Writing Rules

Writing Rules

Rule Example:

[
    {
        "id": "DS185832",
        "name": "Banned C function detected (strcpy)",
        "active": true,
        "tags": [
            "API.DangerousAPI.BannedFunction"
        ],
        "applies_to": [
            "c",
            "cpp",
            "objective-c"
        ],
        "severity": "important",
        "description": "strcpy is frequently dangerous, as it will cause a buffer overflow if the source is larger than the destination.",
        "replacement": "Use strcpy_s or strlcpy if possible. If no safe function is viable, strcpy/strncpy should be proceeded by conditional checks to verify tha that the source string will fit in the destination with a null termnator.",
        "rule_info": "https://github.com/microsoft/devskim/guidance/DS185832.md",
        "patterns": [
            {
                "pattern": "\\bstrcpy\\(([^,]+),([^,\\)]+)\\)",
                "type": "regex",
                "subtype": [
                    "function-call"
                ]
            }
        ],
        "fix_it": [
            {
                "type": "regex_substitute",
                "name": "Change to strcpy_s (Recommended for VC++)",
                "search": "\\bstrcpy\\(([^,]+),([^,\\)]+)\\)",
                "replace": "strcpy_s(\\1, <size of \\1>, \\2)"
            },
            {
                "type": "regex_substitute",
                "name": "Change to strlcpy",
                "search": "\\bstrcpy\\(([^,]+),([^,\\)]+)\\)",
                "replace": "strlcpy(\\1, \\2, <size of \\1>)"
            }
        ]
    }
]