libsast

Generic SAST for Security Engineers. Powered by regex based pattern matcher and semantic aware semgrep.

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Install

pip install semgrep==1.86.0 #For semgrep support
pip install libsast

Pattern Matcher is cross-platform, but Semgrep supports only Mac and Linux.

Command Line Options

$ libsast
usage: libsast [-h] [-o OUTPUT] [-p PATTERN_FILE] [-s SGREP_PATTERN_FILE]
               [--sgrep-file-extensions SGREP_FILE_EXTENSIONS [SGREP_FILE_EXTENSIONS ...]]
               [--file-extensions FILE_EXTENSIONS [FILE_EXTENSIONS ...]]
               [--ignore-filenames IGNORE_FILENAMES [IGNORE_FILENAMES ...]]
               [--ignore-extensions IGNORE_EXTENSIONS [IGNORE_EXTENSIONS ...]]
               [--ignore-paths IGNORE_PATHS [IGNORE_PATHS ...]]
               [--show-progress] [--cpu-core CPU_CORE] [-v]
               [path ...]

positional arguments:
  path                  Path can be file(s) or directories

options:
  -h, --help            show this help message and exit
  -o OUTPUT, --output OUTPUT
                        Output filename to save JSON report.
  -p PATTERN_FILE, --pattern-file PATTERN_FILE
                        YAML pattern file, directory or url
  -s SGREP_PATTERN_FILE, --sgrep-pattern-file SGREP_PATTERN_FILE
                        sgrep rules directory
  --sgrep-file-extensions SGREP_FILE_EXTENSIONS [SGREP_FILE_EXTENSIONS ...]
                        File extensions that should be scanned with semantic
                        grep
  --file-extensions FILE_EXTENSIONS [FILE_EXTENSIONS ...]
                        File extensions that should be scanned with pattern
                        matcher
  --ignore-filenames IGNORE_FILENAMES [IGNORE_FILENAMES ...]
                        File name(s) to ignore
  --ignore-extensions IGNORE_EXTENSIONS [IGNORE_EXTENSIONS ...]
                        File extension(s) to ignore in lower case
  --ignore-paths IGNORE_PATHS [IGNORE_PATHS ...]
                        Path(s) to ignore
  --show-progress       Show scan progress
  --cpu-core CPU_CORE   No of CPU cores to use. Use all cores by default
  -v, --version         Show libsast version

Example Usage

$ libsast -s tests/assets/rules/semantic_grep/ -p tests/assets/rules/pattern_matcher/ tests/assets/files/
{
  "pattern_matcher": {
    "test_regex": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            28,
            28
          ],
          "match_position": [
            1141,
            1149
          ],
          "match_string": ".close()"
        }
      ],
      "metadata": {}
    },
    "test_regex_and": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            3,
            3
          ],
          "match_position": [
            52,
            66
          ],
          "match_string": "webkit.WebView"
        },
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            7,
            7
          ],
          "match_position": [
            194,
            254
          ],
          "match_string": ".loadUrl(\"file:/\" + Environment.getExternalStorageDirectory("
        }
      ],
      "metadata": {}
    },
    "test_regex_and_not": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            42,
            42
          ],
          "match_position": [
            1415,
            1424
          ],
          "match_string": "WKWebView"
        },
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            40,
            40
          ],
          "match_position": [
            1363,
            1372
          ],
          "match_string": "WKWebView"
        }
      ],
      "metadata": {}
    },
    "test_regex_and_or": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            50,
            50
          ],
          "match_position": [
            1551,
            1571
          ],
          "match_string": "telephony.SmsManager"
        },
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            58,
            58
          ],
          "match_position": [
            1973,
            1988
          ],
          "match_string": "sendTextMessage"
        }
      ],
      "metadata": {}
    },
    "test_regex_multiline_and_metadata": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            52,
            52
          ],
          "match_position": [
            1586,
            1684
          ],
          "match_string": "public void onRequestPermissionsResult(int requestCode,String permissions[], int[] grantResults) {"
        },
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            10,
            11
          ],
          "match_position": [
            297,
            368
          ],
          "match_string": "public static ForgeAccount add(Context context, ForgeAccount account) {"
        }
      ],
      "metadata": {
        "cwe": "CWE-1051 Initialization with Hard-Coded Network Resource Configuration Data",
        "description": "This is a rule to test regex",
        "foo": "bar",
        "masvs": "MSTG-STORAGE-3",
        "owasp-mobile": "M1: Improper Platform Usage",
        "owasp-web": "A10: Insufficient Logging & Monitoring",
        "severity": "info"
      }
    },
    "test_regex_or": {
      "files": [
        {
          "file_path": "tests/assets/files/test_matcher.test",
          "match_lines": [
            26,
            26
          ],
          "match_position": [
            1040,
            1067
          ],
          "match_string": "Context.MODE_WORLD_READABLE"
        }
      ],
      "metadata": {}
    }
  },
  "semantic_grep": {
    "errors": [
      {
        "code": 3,
        "level": "warn",
        "message": "Semgrep Core WARN - Lexical error in file tests/assets/files/test_matcher.test:40\n\tunrecognized symbols: !",
        "path": "tests/assets/files/test_matcher.test",
        "type": "Lexical error"
      },
    ],
    "matches": {
      "boto-client-ip": {
        "files": [
          {
            "file_path": "tests/assets/files/example_file.py",
            "match_lines": [
              4,
              4
            ],
            "match_position": [
              24,
              31
            ],
            "match_string": "c = boto3.client(host='8.8.8.8')"
          }
        ],
        "metadata": {
          "cwe": "CWE-1050 Excessive Platform Resource Consumption within a Loop",
          "description": "boto client using IP address",
          "owasp-web": "A8: Insecure Deserialization",
          "severity": "ERROR"
        }
      }
    }
  }
}

Python API

>>> from libsast import Scanner
>>> options = {'match_rules': '/Users/ajinabraham/Code/njsscan/njsscan/rules/pattern_matcher', 'sgrep_rules': '/Users/ajinabraham/Code/njsscan/njsscan/rules/semantic_grep', 'sgrep_extensions': {'', '.js'}, 'match_extensions': {'.hbs', '.sh', '.ejs', '.toml', '.mustache', '.tmpl', '.jade', '.json', '.ect', '.vue', '.yml', '.hdbs', '.tl', '.html', '.haml', '.dust', '.pug', '.tpl'}, 'ignore_filenames': {'bootstrap.min.js', '.DS_Store', 'bootstrap-tour.js', 'd3.min.js', 'tinymce.js', 'codemirror.js', 'tinymce.min.js', 'react-dom.production.min.js', 'react.js', 'jquery.min.js', 'react.production.min.js', 'codemirror-compressed.js', 'axios.min.js', 'angular.min.js', 'raphael-min.js', 'vue.min.js'}, 'ignore_extensions': {'.7z', '.exe', '.rar', '.zip', '.a', '.o', '.tz'}, 'ignore_paths': {'__MACOSX', 'jquery', 'fixtures', 'node_modules', 'bower_components', 'example', 'spec'}, 'show_progress': False}
>>> paths = ['../njsscan/tests/assets/dot_njsscan/']
>>> scanner = Scanner(options, paths)
>>> scanner.scan()
{'pattern_matcher': {'handlebar_mustache_template': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/ignore_ext.hbs', 'match_string': '{{{html}}}', 'match_position': (52, 62), 'match_lines': (1, 1)}], 'metadata': {'id': 'handlebar_mustache_template', 'description': 'The Handlebar.js/Mustache.js template has an unescaped variable. Untrusted user input passed to this variable results in Cross Site Scripting (XSS).', 'type': 'Regex', 'pattern': '{{{.+}}}|{{[ ]*&[\\w]+.*}}', 'severity': 'ERROR', 'input_case': 'exact', 'cwe': "CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')", 'owasp': 'A1: Injection'}}}, 'semantic_grep': {'matches': {'node_aes_ecb': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/lorem_scan.js', 'match_position': (16, 87), 'match_lines': (14, 14), 'match_string': "let decipher = crypto.createDecipheriv('aes-128-ecb', Buffer.from(ENCRYPTION_KEY), iv);"}], 'metadata': {'owasp': 'A9: Using Components with Known Vulnerabilities', 'cwe': 'CWE-327: Use of a Broken or Risky Cryptographic Algorithm', 'description': 'AES with ECB mode is deterministic in nature and not suitable for encrypting large amount of repetitive data.', 'severity': 'ERROR'}}, 'node_tls_reject': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/skip_dir/skip_me.js', 'match_position': (9, 58), 'match_lines': (9, 9), 'match_string': "        process.env['NODE_TLS_REJECT_UNAUTHORIZED'] = '0';"}, {'file_path': '../njsscan/tests/assets/dot_njsscan/skip_dir/skip_me.js', 'match_position': (9, 55), 'match_lines': (18, 18), 'match_string': '        process.env.NODE_TLS_REJECT_UNAUTHORIZED = "0";'}], 'metadata': {'owasp': 'A6: Security Misconfiguration', 'cwe': 'CWE-295: Improper Certificate Validation', 'description': "Setting 'NODE_TLS_REJECT_UNAUTHORIZED' to 0 will allow node server to accept self signed certificates and is not a secure behaviour.", 'severity': 'ERROR'}}, 'node_curl_ssl_verify_disable': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/skip_dir/skip_me.js', 'match_position': (5, 11), 'match_lines': (45, 51), 'match_string': '    curl(url,\n\n        {\n\n            SSL_VERIFYPEER: 0\n\n        },\n\n        function (err) {\n\n            response.end(this.body);\n\n        })'}], 'metadata': {'owasp': 'A6: Security Misconfiguration', 'cwe': 'CWE-599: Missing Validation of OpenSSL Certificate', 'description': 'SSL Certificate verification for node-curl is disabled.', 'severity': 'ERROR'}}, 'regex_injection_dos': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/lorem_scan.js', 'match_position': (5, 37), 'match_lines': (25, 27), 'match_string': '    var key = req.param("key");\n\n    // Regex created from user input\n\n    var re = new RegExp("\\\\b" + key);'}], 'metadata': {'owasp': 'A1: Injection', 'cwe': 'CWE-400: Uncontrolled Resource Consumption', 'description': 'User controlled data in RegExp() can make the application vulnerable to layer 7 DoS.', 'severity': 'ERROR'}}, 'express_xss': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/skip.js', 'match_position': (9, 55), 'match_lines': (7, 10), 'match_string': '        var str = new Buffer(req.cookies.profile, \'base64\').toString();\n\n        var obj = serialize.unserialize(str);\n\n        if (obj.username) {\n\n            res.send("Hello " + escape(obj.username));'}], 'metadata': {'owasp': 'A1: Injection', 'cwe': "CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')", 'description': 'Untrusted User Input in Response will result in Reflected Cross Site Scripting Vulnerability.', 'severity': 'ERROR'}}, 'generic_path_traversal': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/lorem_scan.js', 'match_position': (5, 35), 'match_lines': (36, 37), 'match_string': "    var filePath = path.join(__dirname, '/' + req.query.load);\n\n    fileSystem.readFile(filePath); // ignore: generic_path_traversal"}, {'file_path': '../njsscan/tests/assets/dot_njsscan/lorem_scan.js', 'match_position': (5, 35), 'match_lines': (42, 43), 'match_string': "    var filePath = path.join(__dirname, '/' + req.query.load);\n\n    fileSystem.readFile(filePath); // detect this"}], 'metadata': {'owasp': 'A5: Broken Access Control', 'cwe': 'CWE-23: Relative Path Traversal', 'description': 'Untrusted user input in readFile()/readFileSync() can endup in Directory Traversal Attacks.', 'severity': 'ERROR'}}, 'express_open_redirect': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/lorem_scan.js', 'match_position': (5, 26), 'match_lines': (49, 51), 'match_string': '    var target = req.param("target");\n\n    // BAD: sanitization doesn\'t apply here\n\n    res.redirect(target); //ignore: express_open_redirect'}], 'metadata': {'owasp': 'A1: Injection', 'cwe': "CWE-601: URL Redirection to Untrusted Site ('Open Redirect')", 'description': 'Untrusted user input in redirect() can result in Open Redirect vulnerability.', 'severity': 'ERROR'}}, 'node_deserialize': {'files': [{'file_path': '../njsscan/tests/assets/dot_njsscan/skip.js', 'match_position': (19, 45), 'match_lines': (8, 8), 'match_string': '        var obj = serialize.unserialize(str);'}], 'metadata': {'owasp': 'A8: Insecure Deserialization', 'cwe': 'CWE-502: Deserialization of Untrusted Data', 'description': "User controlled data in 'unserialize()' or 'deserialize()' function can result in Object Injection or Remote Code Injection.", 'severity': 'ERROR'}}}, 'errors': [{'type': 'SourceParseError', 'code': 3, 'short_msg': 'parse error', 'long_msg': 'Could not parse .njsscan as javascript', 'level': 'warn', 'spans': [{'start': {'line': 2, 'col': 20}, 'end': {'line': 2, 'col': 21}, 'source_hash': 'c60298be568bfb1325d92cbb3c0bc1450a25b85bb2e4000bdc3267c05f1c8c73', 'file': '.njsscan', 'context_start': None, 'context_end': None}], 'help': 'If the code appears to be valid, this may be a semgrep bug.'}, {'type': 'SourceParseError', 'code': 3, 'short_msg': 'parse error', 'long_msg': 'Could not parse no_ext_scan as javascript', 'level': 'warn', 'spans': [{'start': {'line': 1, 'col': 3}, 'end': {'line': 1, 'col': 5}, 'source_hash': 'f002e2a715be216987dd1b134e7b9fa6eef28e3caa82dead0109c4cdc489e089', 'file': 'no_ext_scan', 'context_start': None, 'context_end': None}], 'help': 'If the code appears to be valid, this may be a semgrep bug.'}]}}

Write you own Static Analysis tool

With libsast, you can write your own static analysis tools. libsast provides two matching engines:

1. Pattern Matcher
2. Semantic Grep

Pattern Matcher

Currently Pattern Matcher supports any language.

Use Regex 101 to write simple Python Regex rule patterns.

A sample rule looks like

- id: test_regex_or
  message: This is a rule to test regex_or
  input_case: exact
  pattern:
  - MODE_WORLD_READABLE|Context\.MODE_WORLD_READABLE
  - openFileOutput\(\s*".+"\s*,\s*1\s*\)
  severity: error
  type: RegexOr
  metadata:
    owasp-web: a1
    reference: http://foo.bar
    foo: Some extra metadata

A rule consist of

• id : A unique id for the rule.
• message: A description for the rule.
• input_case: It can be exact, upper or lower. Data will be converted to lower case/upper case/as it is before comparing with the regex.
• pattern: List of patterns depends on type.
• severity: It can be error, warning or info.
• type: Pattern Matcher supports Regex, RegexAnd, RegexOr, RegexAndOr, RegexAndNot.
• metadata (optional): Define your own custom fields that you can use as metadata along with standard mappings.

1. Regex - if regex1 in input
2. RegexAnd - if regex1 in input and regex2 in input
3. RegexOr - if regex1 in input or regex2 in input
4. RegexAndOr -  if regex1 in input and (regex2 in input or regex3 in input)
5. RegexAndNot - if regex1 in input and not regex2 in input

Example: Pattern Matcher Rule

Test your pattern matcher rules

$ libsast -p tests/assets/rules/pattern_matcher/patterns.yaml tests/assets/files/

Inbuilt Standard Mapping Support

Metadata fields also support libsast standard mapping.

For example, the metadata field owasp-web: a1 will get expanded at runtime as owasp-web: 'A1: Injection'.

Currently Supports

• OWASP Web Top 10
• OWASP Mobile Top 10
• OWASP MASVS
• CWE

Semantic Grep

Semantic Grep uses semgrep, a fast and syntax-aware semantic code pattern search for many languages: like grep but for code.

Currently it supports Python, Java, JavaScript, Go and C.

Use semgrep.dev to write semantic grep rule patterns.

A sample rule for Python code looks like

rules:
  - id: boto-client-ip
    patterns:
      - pattern-inside: boto3.client(host="...")
      - pattern-regex: '\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'
    message: "boto client using IP address"
    languages: [python]
    severity: ERROR
    metadata:
      owasp-web: a2
      owasp-mobile: m7
      cwe: cwe-1048
      foo: Some extra metadata

See semgrep documentation here.

Example: Semantic Grep Rule

Test your semgrep rules

$ libsast -s tests/assets/rules/semantic_grep/sgrep.yaml tests/assets/files/

Realworld Implementations

• njsscan SAST is built with libsast pattern matcher and semantic grep.
• nodejsscan nodejsscan is a static security code scanner for Node.js applications.
• MobSF Static Code Analyzer for Android and iOS mobile applications.
• mobsfscan mobsfscan is a static security code scanner for Mobile applications built for Android (Java, Kotlin) & iOS (Swift, Objective C).