Log injection¶
ID: js/log-injectionKind: path-problemSecurity severity: 6.1Severity: errorPrecision: mediumTags: - security - external/cwe/cwe-117Query suites: - javascript-security-extended.qls - javascript-security-and-quality.qls
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If unsanitized user input is written to a log entry, a malicious user may be able to forge new log entries.
Forgery can occur if a user provides some input with characters that are interpreted when the log output is displayed. If the log is displayed as a plain text file, then new line characters can be used by a malicious user. If the log is displayed as HTML, then arbitrary HTML may be included to spoof log entries.
Recommendation¶
User input should be suitably sanitized before it is logged.
If the log entries are in plain text then line breaks should be removed from user input, usingString.prototype.replace or similar. Care should also be taken that user input is clearly marked in log entries.
For log entries that will be displayed in HTML, user input should be HTML-encoded before being logged, to prevent forgery and other forms of HTML injection.
Example¶
In the first example, a username, provided by the user, is logged using `console.info`. In the first case, it is logged without any sanitization. In the second case, the username is used to build an error that is logged using `console.error`. If a malicious user provides `username=Guest%0a[INFO]+User:+Admin%0a` as a username parameter, the log entry will be splitted in two different lines, where the second line will be `[INFO]+User:+Admin`.
consthttp=require('http');consturl=require('url');constserver=http.createServer((req,res)=>{letq=url.parse(req.url,true);console.info(`[INFO] User:${q.query.username}`);// BAD: User input logged as-is})server.listen(3000,'127.0.0.1',()=>{});
In the second example,String.prototype.replace is used to ensure no line endings are present in the user input.
consthttp=require('http');consturl=require('url');constserver=http.createServer((req,res)=>{letq=url.parse(req.url,true);// GOOD: remove newlines from user controlled input before loggingletusername=q.query.username.replace(/\n|\r/g,"");console.info(`[INFO] User:${username}`);});server.listen(3000,'127.0.0.1',()=>{});
References¶
OWASP:Log Injection.
Common Weakness Enumeration:CWE-117.