ModSecurity CRS RuleID-960911

Rule ID: 906911

Rule ID	906911
Rule Message	Invalid HTTP Request Line
Rule Summary	Validate request line against the format specified in the HTTP RFC
Impact	4 - Warning
Rule	SecRule REQUEST_LINE "!^(?:(?:[a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?|connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)?|options \*)\s+[\w\./]+|get /[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?)$" \ "phase:1,t:none,t:lowercase,block,msg:'Invalid HTTP Request Line',id:'960911',severity:'4',rev:'2.2.0',logdata:'%{request_line}',tag:'https://www.owasp.org/index.php/ModSecurity_CRS_RuleID-%{tx.id}',tag:'http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.2.1',tag:'RULE_ACCURACY_LEVEL/5',setvar:'tx.msg=%{rule.msg}',setvar:'tx.id=%{rule.id}',setvar:tx.anomaly_score=+%{tx.notice_anomaly_score},setvar:tx.protocol_violation_score=+%{tx.notice_anomaly_score},setvar:'tx.%{rule.id}-PROTOCOL_VIOLATION/INVALID_REQ-%{matched_var_name}=%{matched_var}'"
Detailed Rule Information	Uses rule negation against the regex for positive security. The regex specifies the proper construction of URI request lines such as: "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]] It also outlines proper construction for CONNECT, OPTIONS and GET requests. /// A description of the regular expression: /// /// Beginning of line or string /// Match expression but don't capture it. [(?:[a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?|connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)?|options \*)\s+[\w\./]+|get /[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?] /// Select from 2 alternatives /// (?:[a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?|connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)?|options \*)\s+[\w\./]+ /// Match expression but don't capture it. [[a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?|connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)?|options \*] /// Select from 3 alternatives /// [a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)? /// Any character in this class: [a-z], between 3 and 10 repetitions /// Whitespace, one or more repetitions /// Match expression but don't capture it. [\w{3,7}?://[\w\-\./]*(?::\d+)?], zero or one repetitions /// \w{3,7}?://[\w\-\./]*(?::\d+)? /// Alphanumeric, between 3 and 7 repetitions, as few as possible ///  :// /// Any character in this class: [\w\-\./], any number of repetitions /// Match expression but don't capture it. [:\d+], zero or one repetitions ///  :\d+ ///  : /// Any digit, one or more repetitions /// / /// Any character that is NOT in this class: [?#], any number of repetitions /// Match expression but don't capture it. [\?[^#\s]*], zero or one repetitions /// \?[^#\s]* /// Literal ? /// Any character that is NOT in this class: [#\s], any number of repetitions /// Match expression but don't capture it. [#[\S]*], zero or one repetitions /// #[\S]* /// # /// Any character in this class: [\S], any number of repetitions /// connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)? /// connect /// Space /// Match expression but don't capture it. [\d{1,3}\.], exactly 3 repetitions /// \d{1,3}\. /// Any digit, between 1 and 3 repetitions /// Literal . /// Any digit, between 1 and 3 repetitions /// Literal ., zero or one repetitions /// Match expression but don't capture it. [:\d+], zero or one repetitions ///  :\d+ ///  : /// Any digit, one or more repetitions /// options \* /// options /// Space /// Literal * /// Whitespace, one or more repetitions /// Any character in this class: [\w\./], one or more repetitions /// get /[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)? /// get /// Space /// / /// Any character that is NOT in this class: [?#], any number of repetitions /// Match expression but don't capture it. [\?[^#\s]*], zero or one repetitions /// \?[^#\s]* /// Literal ? /// Any character that is NOT in this class: [#\s], any number of repetitions /// Match expression but don't capture it. [#[\S]*], zero or one repetitions /// #[\S]* /// # /// Any character in this class: [\S], any number of repetitions /// End of line or string
Example Payload	Here is an example payloads taken from HTTPrint (http://net-square.com/httprint/) that will trigger this rule. 127.0.0.1 - - [14/Sep/2010:11:51:43 -0400] "\x16\x03" 501 214 TI@aD8CoAWYAAAOFHNMAAACA
Example Audit Log Entry	Include an example ModSecurity Audit Log Entry for when this rule matchs. --1167a167-A-- [14/Sep/2010:11:51:43 --0400] TI@aD8CoAWYAAAOFHNMAAACA 127.0.0.1 51285 127.0.0.1 80 --1167a167-B-- ^V^C --1167a167-F-- --1167a167-H-- Message: Match of "rx ^(?:(?:[a-z]{3,10}\\s+(?:\\w{3,7}?://[\\w\\-\\./]*(?::\\d+)?)?/[^?#]*(?:\\?[^#\\s]*)?(?:#[\\S]*)?|connect (?:\\d{1,3}\\.){3}\\d{1,3}\\.?(?::\\d+)?|options \\*)\\s+[\\w\\./]+|get /[^?#]*(?:\\?[^#\\s]*)?(?:#[\\S]*)?)$" against "REQUEST_LINE" required. [file "/usr/local/apache/conf/modsec_current/base_rules/modsecurity_crs_20_protocol_violations.conf"] [line "34"] [id "960911"] [rev "2.0.8"] [msg "Invalid HTTP Request Line"] [severity "WARNING"] [tag "http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.2.1"] Apache-Error: [file "core.c"] [line 3773] [level 3] Invalid method in request \\x16\\x03 Stopwatch: 1284479503453580 43606 (4888 42377 -) Producer: ModSecurity for Apache/2.5.12 (http://www.modsecurity.org/); core ruleset/2.0.8. Server: Apache/2.2.12 (Unix) mod_ssl/2.2.12 OpenSSL/0.9.8l DAV/2 --1167a167-Z--
Attack Scenarios	Some malformed URIs are created on purpose as part of HTTP fingerprinting scans - http://projects.webappsec.org/Fingerprinting Other times, these are caused by poorly written web clients.
Ease of Attack	Easy
Ease of Detection	Easy with either regular expressions or by monitoring Apache error logging in phase:5
False Positives	None known If there are any known false positives - specify them here Also sign-up for the Reporting False Positives mail-list here: https://lists.sourceforge.net/lists/listinfo/mod-security-report-false-positives Send FP Report emails here: mod-security-report-false-positiveslists.sourceforge.net
False Negatives	None known
Rule Maturity	8 10 point scale (0-9) where: 0 = Beta/Experimental 9 = Heavily Tested
Rule Accuracy	8 10 point scale (0-9) where: 0 = High % of FP 5 = No false positives reported
Rule Documentation Contributor(s)	Ryan Barnett - ryan.barnettowasp.org
Additional References	http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.2.1