Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read a value from a request object. The value then is logged.

...
DATA log_msg TYPE bal_s_msg.

val = request->get_form_field( 'val' ).

log_msg-msgid = 'XY'.
log_msg-msgty = 'E'.
log_msg-msgno = '123'.
log_msg-msgv1 = 'VAL: '.
log_msg-msgv2 = val.

CALL FUNCTION 'BAL_LOG_MSG_ADD'
  EXPORTING
    I_S_MSG          = log_msg
  EXCEPTIONS
    LOG_NOT_FOUND    = 1
    MSG_INCONSISTENT = 2
    LOG_IS_FULL      = 3
    OTHERS           = 4.
...

If a user submits the string "FOO" for val, the following entry is logged:

XY E 123 VAL: FOO

However, if an attacker submits the string "FOO XY E 124 VAL: BAR", the following entry is logged:

XY E 123 VAL: FOO XY E 124 VAL: BAR

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

var params:Object = LoaderInfo(this.root.loaderInfo).parameters;
var val:String = String(params["username"]);
var value:Number = parseInt(val);
if (value == Number.NaN) {
  trace("Failed to parse val = " + val);
}

If a user submits the string "twenty-one" for val, the following entry is logged:

Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

Failed to parse val=twenty-one

User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1.Data enters an application from an untrusted source.

2.The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

...
string val = (string)Session["val"];
try {
int value = Int32.Parse(val);
}
catch (FormatException fe) {
log.Info("Failed to parse val= " + val);
}
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val=twenty-one

INFO: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending upon the nature of the application, log files can be reviewed manually as required, or culled automatically by tools that search the logs for important data points or trends.

Examination of the log files can be hindered or conclusions based on log data can be wrong if an attacker is allowed to supply data to the application that is subsequently logged verbatim. An attacker might insert false entries into the log file by including log entry separator characters in their data. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker injects code or other commands into the log file and takes advantage of a vulnerability in the log processing utility [2].

Example: The following code from a CGI script accepts a string submitted by the user and attempts to convert it into the long integer value it represents. If the value fails to parse as an integer, then its value is logged with an error message indicating what happened.

long value = strtol(val, &endPtr, 10);
if (*endPtr != '\0')
	syslog(LOG_INFO,"Illegal value = %s",val);
...

If a user submits the string "twenty-one" for val, the following entry is logged:

Illegal value=twenty-one

However, if an attacker submits the string "twenty-one\n\nINFO: User logged out=evil", the following entry is logged:

	INFO: Illegal value=twenty-one

	INFO: User logged out=evil

Clearly, the attacker may use this same mechanism to insert arbitrary log entries. For this type of log forging attack to be effective, an attacker must first identify valid log entry formats, but this can often be accomplished by through system information leaks in the target application.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker might insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker might render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read a value from an HTML form. The value then is logged.

...
01  LOGAREA.
     05  VALHEADER        PIC X(50) VALUE 'VAL: '.
     05  VAL              PIC X(50).
...

EXEC CICS
  WEB READ
  FORMFIELD(NAME)
  VALUE(VAL)
  ...
END-EXEC.

EXEC DLI
  LOG
  FROM(LOGAREA)
  LENGTH(50)
END-EXEC.
...

If a user submits the string "FOO" for VAL, the following entry is logged:

VAL: FOO

However, if an attacker submits the string "FOO VAL: BAR", the following entry is logged:

VAL: FOO VAL: BAR

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.


2. The data is written to an application or system log file.


Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a web form. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

<cflog file="app_log" application="No" Thread="No" 
       text="Failed to parse val="#Form.val#">

If a user submits the string "twenty-one" for val, the following entry is logged:

"Information",,"02/28/01","14:50:37",,"Failed to parse val=twenty-one"

However, if an attacker submits the string "twenty-one%0a%0a%22Information%22%2C%2C%2202/28/01%22%2C%2214:53:40%22%2C%2C%22User%20logged%20out:%20badguy%22", the following entry is logged:

"Information",,"02/28/01","14:50:37",,"Failed to parse val=twenty-one"

"Information",,"02/28/01","14:53:40",,"User logged out: badguy"

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events, view transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

    func someHandler(w http.ResponseWriter, r *http.Request){
        r.parseForm()
        name := r.FormValue("name")
        logout := r.FormValue("logout")
        ...
        if (logout){
            ...
        } else {
            log.Printf("Attempt to log out: name: %s logout: %s", name, logout)
        }
    }

If a user submits the string "twenty-one" for logout and he was able to create a user with name "admin", the following entry is logged:

Attempt to log out: name: admin logout: twenty-one

However, if an attacker is able to create a username "admin+logout:+1+++++++++++++++++++++++", the following entry is logged:

Attempt to log out: name: admin logout: 1                       logout: twenty-one

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

var cp = require('child_process');
var http = require('http');
var url = require('url');

function listener(request, response){
  var val = url.parse(request.url, true)['query']['val'];
  if (isNaN(val)){
    console.log("INFO: Failed to parse val = " + val);
  }
  ...
}
...
http.createServer(listener).listen(8080);
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val = twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val=twenty-one

INFO: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending upon the nature of the application, log files can be reviewed manually as required, or culled automatically by tools that search the logs for important data points or trends.

Examination of the log files can be hindered or conclusions based on log data can be wrong if an attacker is allowed to supply data to the application that is subsequently logged verbatim. An attacker might insert false entries into the log file by including log entry separator characters in their data. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker injects code or other commands into the log file and takes advantage of a vulnerability in the log processing utility [2].

Example 1: The following code from a CGI script accepts a string submitted by the user and attempts to convert it into the long integer value it represents. If the value fails to parse as an integer, then its value is logged with an error message indicating what happened.

long value = strtol(val, &endPtr, 10);
if (*endPtr != '\0')
	NSLog("Illegal value = %s",val);
...

If a user submits the string "twenty-one" for val, the following entry is logged:

    INFO: Illegal value=twenty-one

However, if an attacker submits the string "twenty-one\n\nINFO: User logged out=evil", the following entry is logged:

	INFO: Illegal value=twenty-one

	INFO: User logged out=evil

Clearly, the attacker may use this same mechanism to insert arbitrary log entries. For this type of log forging attack to be effective, an attacker must first identify valid log entry formats, but this can often be accomplished through system information leaks in the target application.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

<?php
    $name   =$_GET['name'];
    ...
    $logout =$_GET['logout'];

    if(is_numeric($logout))
    {
        ...
    }
    else
    {
        trigger_error("Attempt to log out: name: $name logout: $val");
    }
?>

If a user submits the string "twenty-one" for logout and he was able to create a user with name "admin", the following entry is logged:

PHP Notice: Attempt to log out: name: admin logout: twenty-one

However, if an attacker is able to create a username "admin+logout:+1+++++++++++++++++++++++", the following entry is logged:

PHP Notice: Attempt to log out: name: admin logout: 1                       logout: twenty-one

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

    name = req.field('name')
    ...
    logout = req.field('logout')

    if (logout):
        ...
    else:
        logger.error("Attempt to log out: name: %s logout: %s" % (name,logout))

If a user submits the string "twenty-one" for logout and he was able to create a user with name "admin", the following entry is logged:

Attempt to log out: name: admin logout: twenty-one

However, if an attacker is able to create a username "admin+logout:+1+++++++++++++++++++++++", the following entry is logged:

Attempt to log out: name: admin logout: 1                       logout: twenty-one

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

...
val = req['val']
unless val.respond_to?(:to_int)
  logger.info("Failed to parse val")
  logger.info(val)
end
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val
INFO: twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val
INFO: twenty-one

INFO: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending upon the nature of the application, log files can be reviewed manually as required, or culled automatically by tools that search the logs for important data points or trends.

Examination of the log files can be hindered or conclusions based on log data can be wrong if an attacker is allowed to supply data to the application that is subsequently logged verbatim. An attacker might insert false entries into the log file by including log entry separator characters in their data. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker injects code or other commands into the log file and takes advantage of a vulnerability in the log processing utility [2].

Example 1: The following code accepts a string submitted by the user and attempts to convert it into the integer value it represents. If the value fails to parse as an integer, then its value is logged with an error message indicating what happened.

...
let num = Int(param)
if num == nil {
    NSLog("Illegal value = %@", param)
}
...

If a user submits the string "twenty-one" for val, the following entry is logged:

    INFO: Illegal value = twenty-one

However, if an attacker submits the string "twenty-one\n\nINFO: User logged out=evil", the following entry is logged:

	INFO: Illegal value=twenty-one

	INFO: User logged out=evil

Clearly, the attacker may use this same mechanism to insert arbitrary log entries. For this type of log forging attack to be effective, an attacker must first identify valid log entry formats, but this can often be accomplished through system information leaks in the target application.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

...
Dim Val As Variant
Dim Value As Integer
Set Val = Request.Form("val")
If IsNumeric(Val) Then
	Set Value = Val
Else
	App.EventLog "Failed to parse val=" & Val, 1
End If
...

If a user submits the string "twenty-one" for val, the following entry is logged:

Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0a+User+logged+out%3dbadguy", the following entry is logged:

Failed to parse val=twenty-one

User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

A cross-site request forgery (CSRF) vulnerability occurs when:
1. A Web application uses session cookies.

2. The application acts on an HTTP request without verifying that the request was made with the user's consent.

By default, Visualforce pages are rendered with hidden form fields that serve as anti-CSRF tokens. These tokens are included in the requests that are sent from within the page, and the server checks the validity of the tokens before executing the corresponding action methods or commands. However, this built-in defense does not apply to page action methods and custom page controller constructors because they are executed before the anti-CSRF tokens are generated during page load.

Example 1: The following Visualforce page declares a custom contoller MyAccountActions and a page action method pageAction(). The pageAction() method is executed when visiting the page URL, and the server does not check for anti-CSRF tokens.

<apex:page controller="MyAccountActions" action="{!pageAction}">
    ...
</apex:page>

public class MyAccountActions {

    ...
    public void pageAction() {
        Map<String,String> reqParams = ApexPages.currentPage().getParameters();
        if (params.containsKey('id')) {
            Id id = reqParams.get('id');
            Account acct = [SELECT Id,Name FROM Account WHERE Id = :id];
            delete acct;
        }
    }
    ...
}

An attacker might set up a malicious website that contains the following code:

<img src="http://my-org.my.salesforce.com/apex/mypage?id=YellowSubmarine" height=1 width=1/>

If an administrator for the Visualforce page visits the malicious page while having an active session on the site, they will unwittingly delete accounts for the attacker.

A cross-site request forgery (CSRF) vulnerability occurs when:
1. A web application uses session cookies.

2. The application acts on an HTTP request without verifying that the request was made with the user's consent.



A nonce is a cryptographic random value that is sent with a message to prevent replay attacks. If the request does not contain a nonce that proves its provenance, the code that handles the request is vulnerable to a CSRF attack (unless it does not change the state of the application). This means a web application that uses session cookies has to take special precautions to ensure that an attacker can't trick users into submitting bogus requests. Imagine a web application that allows administrators to create new accounts as follows:

  var req = new XMLHttpRequest();
  req.open("POST", "/new_user", true);
  body = addToPost(body, new_username);
  body = addToPost(body, new_passwd);
  req.send(body);

An attacker might set up a malicious web site that contains the following code.

  var req = new XMLHttpRequest();
  req.open("POST", "http://www.example.com/new_user", true);
  body = addToPost(body, "attacker");
  body = addToPost(body, "haha");
  req.send(body);

If an administrator for example.com visits the malicious page while she has an active session on the site, she will unwittingly create an account for the attacker. This is a CSRF attack. It is possible because the application does not have a way to determine the provenance of the request. Any request could be a legitimate action chosen by the user or a faked action set up by an attacker. The attacker does not get to see the Web page that the bogus request generates, so the attack technique is only useful for requests that alter the state of the application.

Applications that pass the session identifier in the URL rather than as a cookie do not have CSRF problems because there is no way for the attacker to access the session identifier and include it as part of the bogus request.
CSRF is entry number five on the 2007 OWASP Top 10 list.

A cross-site request forgery (CSRF) vulnerability occurs when:
1. A Web application uses session cookies.

2. The application acts on an HTTP request without verifying that the request was made with the user's consent.

A nonce is a cryptographic random value that is sent with a message to prevent replay attacks. If the request does not contain a nonce that proves its provenance, the code that handles the request is vulnerable to a CSRF attack (unless it does not change the state of the application). This means a Web application that uses session cookies has to take special precautions in order to ensure that an attacker can't trick users into submitting bogus requests. Imagine a Web application that allows administrators to create new accounts by submitting this form:

<form method="POST" action="/new_user" >
Name of new user: <input type="text" name="username">
Password for new user: <input type="password" name="user_passwd">
<input type="submit" name="action" value="Create User">
</form>

An attacker might set up a Web site with the following:

<form method="POST" action="http://www.example.com/new_user">
<input type="hidden" name="username" value="hacker">
<input type="hidden" name="user_passwd" value="hacked">
</form>
<script>
document.usr_form.submit();
</script>

If an administrator for example.com visits the malicious page while she has an active session on the site, she will unwittingly create an account for the attacker. This is a CSRF attack. It is possible because the application does not have a way to determine the provenance of the request. Any request could be a legitimate action chosen by the user or a faked action set up by an attacker. The attacker does not get to see the Web page that the bogus request generates, so the attack technique is only useful for requests that alter the state of the application.

Applications that pass the session identifier in the URL rather than as a cookie do not have CSRF problems because there is no way for the attacker to access the session identifier and include it as part of the bogus request.

A cross-site request forgery (CSRF) vulnerability occurs when:
1. A Web application uses session cookies.

2. The application acts on an HTTP request without verifying that the request was made with the user's consent.

A nonce is a cryptographic random value that is sent with a message to prevent replay attacks. If the request does not contain a nonce that proves its provenance, the code that handles the request is vulnerable to a CSRF attack (unless it does not change the state of the application). This means a Web application that uses session cookies has to take special precautions in order to ensure that an attacker can't trick users into submitting bogus requests. Imagine a Web application that allows administrators to create new accounts as follows:

By default Play Framework adds protection against CSRF, but it can be disabled globally or for certain routes.

Example: The following route definition disables the CSRF protection for the buyItem controller method.

+ nocsrf
POST    /buyItem     controllers.ShopController.buyItem

If a user is tricked into visiting a malicious page while she has an active session for shop.com, she will unwittingly buy items for the attacker. This is a CSRF attack. It is possible because the application does not have a way to determine the provenance of the request. Any request could be a legitimate action chosen by the user or a faked action set up by an attacker. The attacker does not get to see the Web page that the bogus request generates, so the attack technique is only useful for requests that alter the state of the application.

Applications that pass the session identifier in the URL rather than as a cookie do not have CSRF problems because there is no way for the attacker to access the session identifier and include it as part of the bogus request.

A cross-site request forgery (CSRF) vulnerability occurs when:
1. A Web application uses session cookies.

2. The application acts on an HTTP request without verifying that the request was made with the user's consent.



A nonce is a cryptographic random value that is sent with a message to prevent replay attacks. If the request does not contain a nonce that proves its provenance, the code that handles the request is vulnerable to a CSRF attack (unless it does not change the state of the application). This means a Web application that uses session cookies has to take special precautions in order to ensure that an attacker can't trick users into submitting bogus requests. Imagine a Web application that allows administrators to create new accounts by submitting this form:

<form method="POST" action="/new_user" >
  Name of new user: <input type="text" name="username">
  Password for new user: <input type="password" name="user_passwd">
    <input type="submit" name="action" value="Create User">
</form>

An attacker might set up a Web site with the following:

<form method="POST" action="http://www.example.com/new_user">
  <input type="hidden" name="username" value="hacker">
  <input type="hidden" name="user_passwd" value="hacked">
</form>
<script>
  document.usr_form.submit();
</script>

If an administrator for example.com visits the malicious page while she has an active session on the site, she will unwittingly create an account for the attacker. This is a CSRF attack. It is possible because the application does not have a way to determine the provenance of the request. Any request could be a legitimate action chosen by the user or a faked action set up by an attacker. The attacker does not get to see the Web page that the bogus request generates, so the attack technique is only useful for requests that alter the state of the application.

Applications that pass the session identifier in the URL rather than as a cookie do not have CSRF problems because there is no way for the attacker to access the session identifier and include it as part of the bogus request.

CSRF is entry number five on the 2007 OWASP Top 10 list.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection will originate from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example 1: In the following example, an attacker can control the URL to which the server is connecting.

...
PageReference ref = ApexPages.currentPage();
Map<String,String> params = ref.getParameters();
HttpRequest req = new HttpRequest();
req.setEndpoint(params.get('url'));
HTTPResponse res = new Http().send(req);

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https such as:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following types of attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection will originate from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

string url = Request.Form["url"];
HttpClient client = new HttpClient();
HttpResponseMessage response = await client.GetAsync(url);

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection will originate from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

char *url = maliciousInput(); 
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, url);
CURLcode res = curl_easy_perform(curl);

An attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https such as:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using the file:// scheme.
- On Windows systems, using the file:// scheme and UNC paths can enable an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection originates from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

  ...
  final server = await HttpServer.bind('localhost', 18081);
  server.listen((request) async {
      final headers = request.headers;
      final url = headers.value('url');
      final client = IOClient();
      final response = await client.get(Uri.parse(url!));
      ...
  }

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https such as:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker might influence a network connection made by the application server. The network connection originates from the application server's internal IP address and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL the server is connecting to.

url := request.Form.Get("url")
res, err =: http.Get(url)
...

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and the libraries used to establish the connection. For example, controlling the URI scheme enables the attacker to use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- Scan and access internal shares on Windows systems with file:// scheme and UNC paths.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker may influence a network connection made by the application server. The network connection will originate from the application server's internal IP address and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

var http = require('http');
var url = require('url');

function listener(request, response){
  var request_url = url.parse(request.url, true)['query']['url'];
  http.request(request_url)
  ...
}
...
http.createServer(listener).listen(8080);
...

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection will originate from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

val url: String = request.getParameter("url")
val httpclient: CloseableHttpClient = HttpClients.createDefault()
val httpGet = HttpGet(url)
val response1: CloseableHttpResponse = httpclient.execute(httpGet)

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker may influence a network connection made by the application server. The network connection will originate from the application server's internal IP address and an attacker will be able to use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

$url = $_GET['url'];
$c = curl_init();
curl_setopt($c, CURLOPT_POST, 0);
curl_setopt($c,CURLOPT_URL,$url);
$response=curl_exec($c);
curl_close($c);

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker may influence a network connection made by the application server. The network connection will originate from the application server's internal IP address and an attacker will be able to use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

url = request.GET['url']
handle = urllib.urlopen(url)

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker may influence a network connection made by the application server. The network connection will originate from the application server's internal IP address and an attacker will be able to use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

url = req['url']
Net::HTTP.get(url)

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker may influence a network connection made by the application server. The network connection will originate from the application server's internal IP address and an attacker will be able to use this connection to bypass network controls and scan or attack internal resources that are not otherwise exposed.

Example: In the following example, an attacker can control the URL to which the server is connecting.

def getFile(url: String) = Action { request =>
    ...
    val url = request.body.asText.getOrElse("http://google.com")

    ws.url(url).get().map { response =>
      Ok(s"Request sent to $url")
    }
    ...
}

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Attack vulnerable programs running on the application server or on the intranet.
- Attack internal/external web applications using Injection attacks or CSRF.
- Access local files using file:// scheme.
- On Windows systems, file:// scheme and UNC paths can allow an attacker to scan and access internal shares.
- Perform a DNS cache poisoning attack.

A Server-Side Request Forgery occurs when an attacker can influence a network connection made by the application server. The network connection will originate from the application server's internal IP and an attacker can use this connection to bypass network controls and scan or attack internal resources that are otherwise not exposed.

Example 1: Example of an actual user checking details of a given product.

POST /checkDetails HTTP/1.1

url=https://example.com/product/1 

Example 2: Few examples of how an attacker that has control over the url parameter can tamper the request in Example 1.

POST /checkDetails HTTP/1.1

url=https://localhost.com/admin

POST /checkDetails HTTP/1.1

url=file:///etc/passwd

The attacker's ability to hijack the network connection depends on the specific part of the URI that can be controlled, and on the libraries used to establish the connection. For example, controlling the URI scheme lets the attacker use protocols different from http or https like:

- up://
- ldap://
- jar://
- gopher://
- mailto://
- ssh2://
- telnet://
- expect://

An attacker can leverage this hijacked network connection to perform the following attacks:

- Port Scanning of intranet resources.
- Bypass firewalls.
- Access authorization credentials.
- Attack vulnerable programs running on the application server or on the intranet.
- Gain remote code execution.
- Access local files.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.



2. The data is written to an application or system log file.



Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker might inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following REST endpoint attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

@HttpGet
global static void doGet() {
    RestRequest req = RestContext.request;
    String val = req.params.get('val');
    try {
        Integer i = Integer.valueOf(val);
        ...
    } catch (TypeException e) {
        System.Debug(LoggingLevel.INFO, 'Failed to parse val: '+val);
    }
}

If a user submits the string "twenty-one" for val, the following entry is logged:

Failed to parse val: twenty-one

However, if an attacker submits the string "twenty-one%0a%0aUser+logged+out%3dbadguy", the following entry is logged:

Failed to parse val: twenty-one

User logged out=badguy

Clearly, attackers might use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

  ...
          String val = request.Params["val"];
          try {
                  int value = Int.Parse(val);
          }
          catch (FormatException fe) {
                  log.Info("Failed to parse val = " + val);
          }
  ...
  

If a user submits the string "twenty-one" for val, the following entry is logged:

  INFO: Failed to parse val=twenty-one
  

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

  INFO: Failed to parse val=twenty-one

  INFO: User logged out=badguy
  

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Some think that in the mobile world, classic web application vulnerabilities, such as log forging, do not make sense -- why would the user attack themself? However, keep in mind that the essence of mobile platforms is applications that are downloaded from various sources and run alongside each other on the same device. The likelihood of running a piece of malware next to a banking application is high, which necessitates expanding the attack surface of mobile applications to include inter-process communication.

Example 2: The following code adapts Example 1 to the Android platform.

  ...
          String val = this.Intent.Extras.GetString("val");
          try {
                  int value = Int.Parse(val);
          }
          catch (FormatException fe) {
                  Log.E(TAG, "Failed to parse val = " + val);
          }
  ...
  

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files might be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files might be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker can insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker can render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, an attacher can use corrupted log files to cover their tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker might inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message to indicate what happened.

...
    var idValue string

    idValue = req.URL.Query().Get("id")
    num, err := strconv.Atoi(idValue)

    if err != nil {
        sysLog.Debug("Failed to parse value: " + idValue)
    }
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val=twenty-one

INFO: User logged out=badguy

Clearly, attackers can use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

var cp = require('child_process');
var http = require('http');
var url = require('url');

function listener(request, response){
  var val = url.parse(request.url, true)['query']['val'];
  if (isNaN(val)){
    console.error("INFO: Failed to parse val = " + val);
  }
  ...
}
...
http.createServer(listener).listen(8080);
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val=twenty-one

INFO: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

...
val = request.GET["val"]
try:
  int_value = int(val)
except:
  logger.debug("Failed to parse val = " + val)
...

If a user submits the string "twenty-one" for val, the following entry is logged:

INFO: Failed to parse val=twenty-one

However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged:

INFO: Failed to parse val=twenty-one

INFO: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Log forging vulnerabilities occur when:

1. Data enters an application from an untrusted source.

2. The data is written to an application or system log file.

Applications typically use log files to store a history of events or transactions for later review, statistics gathering, or debugging. Depending on the nature of the application, the task of reviewing log files may be performed manually on an as-needed basis or automated with a tool that automatically culls logs for important events or trending information.

Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker may be able to render the file unusable by corrupting the format of the file or injecting unexpected characters. A more subtle attack might involve skewing the log file statistics. Forged or otherwise, corrupted log files can be used to cover an attacker's tracks or even to implicate another party in the commission of a malicious act [1]. In the worst case, an attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility [2].

Example 1: The following web application code attempts to read an integer value from a request object. If the value fails to parse as an integer, then the input is logged with an error message indicating what happened.

...
val = req['val']
unless val.respond_to?(:to_int)
  logger.debug("Failed to parse val")
  logger.debug(val)
end
...

If a user submits the string "twenty-one" for val, the following entry is logged:

DEBUG: Failed to parse val
DEBUG: twenty-one

However, if an attacker submits the string "twenty-one%0a%DEBUG:+User+logged+out%3dbadguy", the following entry is logged:

DEBUG: Failed to parse val
DEBUG: twenty-one

DEBUG: User logged out=badguy

Clearly, attackers may use this same mechanism to insert arbitrary log entries.

Example 1: The first .NET program that a developer learns to write is the following:

public class MyClass {
  ...
    Console.WriteLine("hello world");
  ...
}

While most programmers go on to learn many nuances and subtleties about .NET, a surprising number hang on to this first lesson and never give up on writing messages to standard output using Console.WriteLine().

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features like logging levels, uniform formatting, a logger identifier, timestamps, and, perhaps most critically, the ability to direct the log messages to the right place. When the use of system output streams is jumbled together with the code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Developers widely accept the need for structured logging, but many continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, use of Console.WriteLine may indicate an oversight in the move to a structured logging system.

Example 1: Typically, the first Go program that a developer learns to write is the following:

...

func foo(){
    fmt.Println("Hello World")
}

While most developers go on to learn many nuances and subtleties about Go, some never give up on writing messages to standard output using fmt.Println().

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features such as logging levels, uniform formatting, a logger identifier, timestamps, and the ability to direct log messages to a proper location. When the use of system output streams is jumbled together with code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Structured logging is widely accepted but many developers continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, logging to os.Stdout or os.Stderr might indicate an oversight in the move to a structured logging system.

Example 1: A simple program an early Node.js developer may write to read from stdin and write it back to stdout again may look like the following:

process.stdin.on('readable', function(){
    var s = process.stdin.read();
    if (s != null){
      process.stdout.write(s);
    }
});

While most programmers go on to learn many nuances and subtleties about JavaScript and Node.js in particular, many will hang on to this first lesson and never give up on writing messages to standard output using process.stdout.write().

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features like logging levels, uniform formatting, a logger identifier, timestamps, and, perhaps most critically, the ability to direct the log messages to the right place. When the use of system output streams is jumbled together with the code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Developers widely accept the need for structured logging, but many continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, use of process.stdout or process.stderr may indicate an oversight in the move to a structured logging system.

Example 1: The first Kotlin program that a developer learns to write is the following:

class MyClass {
    ...
        println("hello world")
    ...
    }
}

While most programmers go on to learn many nuances and subtleties about Kotlin, a surprising number hang on to this first lesson and never give up on writing messages to standard output using print or println.

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features like logging levels, uniform formatting, a logger identifier, timestamps, and, perhaps most critically, the ability to direct the log messages to the right place. When the use of system output streams is jumbled together with the code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Developers widely accept the need for structured logging, but many continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, use of the standard ouput or error stream may indicate an oversight in the move to a structured logging system.

Example 1: The first Python program that a developer learns to write usually looks like this:

sys.stdout.write("hello world")

While most programmers go on to learn many nuances and subtleties about Python, a surprising number hang on to this first lesson and never give up on writing messages to standard output.

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features like logging levels, uniform formatting, a logger identifier, timestamps, and, perhaps most critically, the ability to direct the log messages to the right place. When the use of system output streams is jumbled together with the code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Developers widely accept the need for structured logging, but many continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, use of sys.stdout or sys.stderr may indicate an oversight in the move to a structured logging system.

Example 1: The first Ruby program that a developer learns to write often will include functionality such as:

...
puts "hello world"
...

While most programmers go on to learn many nuances and subtleties about Ruby, a surprising number hang on to this first lesson and never give up on writing messages to standard output using Kernel.puts.

The problem is that writing directly to standard output or standard error is often used as an unstructured form of logging. Structured logging facilities provide features like logging levels, uniform formatting, a logger identifier, timestamps, and, perhaps most critically, the ability to direct the log messages to the right place. When the use of system output streams is jumbled together with the code that uses loggers properly, the result is often a well-kept log that is missing critical information.

Developers widely accept the need for structured logging, but many continue to use system output streams in their "pre-production" development. If the code you are reviewing is past the initial phases of development, use of Kernel.puts,Kernel.warn or Kernel.printf may indicate an oversight in the move to a structured logging system.
If there is a company policy not to use these APIs, this could still be worked around via the use of a logging system to then print the information to a system output stream.

Example 2: The following code uses the Logger class, but logs information to a system output stream:

require 'logger'
...
logger = Logger.new($stdout)
logger.info("hello world")
...