cli: allow ignoring specific PYSEC ids

This commit introduces a new flag to pip-audit's CLI (--ignore-vuln)
that takes a string representing a PYSEC id, if any of the packages
scanned detect said vulnerability, it will be ignored in the final
report.

This allows users of pip-audit to ignore certain vulnerabilities that
they may deem not exploitable for whatever reason.

The flag can be used multiple times to ignore multiple PYSEC ids.

Closes #245

CHANGELOG.md

@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 All versions prior to 0.0.9 are untracked.
 
+## [Unreleased]
+
+### Added
+
+* CLI: The `--ignore-vuln` option has been added, allowing users to
+  specify PYSEC ids to ignore during the final report.
+  ([#275](https://github.com/trailofbits/pip-audit/pull/275))
+
 ## [2.2.1] - 2022-05-02
 
 ### Fixed

pip_audit/_cli.py

@@ -287,6 +287,14 @@ def _parser() -> argparse.ArgumentParser:
         # argparse's default renderer uses __repr__ and produces
         # a pretty unpleasant help message.
     )
+    parser.add_argument(
+        "--ignore-vuln",
+        type=str,
+        action="append",
+        dest="ignore_vuln",
+        default=[],
+        help="ignore a specific vulnerability by its PYSEC id",
+    )
     return parser
 
 
@@ -390,6 +398,7 @@ def audit() -> None:
         pkg_count = 0
         vuln_count = 0
         skip_count = 0
+        vuln_ignore_count = 0
         for (spec, vulns) in auditor.audit(source):
             if spec.is_skipped():
                 spec = cast(SkippedDependency, spec)
@@ -401,6 +410,10 @@ def audit() -> None:
             else:
                 spec = cast(ResolvedDependency, spec)
                 state.update_state(f"Auditing {spec.name} ({spec.version})")
+            if args.ignore_vuln:
+                filtered_vulns = [v for v in vulns if v.id not in args.ignore_vuln]
+                vuln_ignore_count += len(vulns) - len(filtered_vulns)
+                vulns = filtered_vulns
             result[spec] = vulns
             if len(vulns) > 0:
                 pkg_count += 1
@@ -442,7 +455,8 @@ def audit() -> None:
     if vuln_count > 0:
         summary_msg = (
             f"Found {vuln_count} known "
-            f"{'vulnerability' if vuln_count == 1 else 'vulnerabilities'} "
+            f"{'vulnerability' if vuln_count == 1 else 'vulnerabilities'}"
+            f"{(vuln_ignore_count and ', ignored %d ' % vuln_ignore_count) or ' '}"
             f"in {pkg_count} {'package' if pkg_count == 1 else 'packages'}"
         )
         if args.fix:
@@ -457,7 +471,14 @@ def audit() -> None:
         if pkg_count != fixed_pkg_count:
             sys.exit(1)
     else:
-        print("No known vulnerabilities found", file=sys.stderr)
+        summary_msg = "No known vulnerabilities found"
+        if vuln_ignore_count:
+            summary_msg += f", {vuln_ignore_count} ignored"
+
+        print(
+            summary_msg,
+            file=sys.stderr,
+        )
         # If our output format is a "manifest" format we always emit it,
         # even if nothing other than a dependency summary is present.
         if skip_count > 0 or formatter.is_manifest:

test/test_cli.py

@@ -10,9 +10,12 @@
         ([], 1, 1, "Found 1 known vulnerability in 1 package"),
         ([], 2, 1, "Found 2 known vulnerabilities in 1 package"),
         ([], 2, 2, "Found 2 known vulnerabilities in 2 packages"),
+        (["--ignore-vuln", "bar"], 2, 2, "Found 2 known vulnerabilities, ignored 1 in 2 packages"),
         (["--fix"], 1, 1, "fixed 1 vulnerability in 1 package"),
         (["--fix"], 2, 1, "fixed 2 vulnerabilities in 1 package"),
         (["--fix"], 2, 2, "fixed 2 vulnerabilities in 2 packages"),
+        ([], 0, 0, "No known vulnerabilities found"),
+        (["--ignore-vuln", "bar"], 0, 1, "No known vulnerabilities found, 1 ignored"),
     ],
 )
 def test_plurals(capsys, monkeypatch, args, vuln_count, pkg_count, expected):
@@ -35,6 +38,9 @@ def test_plurals(capsys, monkeypatch, args, vuln_count, pkg_count, expected):
         for i in range(pkg_count)
     ]
 
+    if "--ignore-vuln" in args:
+        result[0][1].append(pretend.stub(id="bar"))
+
     auditor = pretend.stub(audit=lambda a: result)
     monkeypatch.setattr(pip_audit._cli, "Auditor", lambda *a, **kw: auditor)