support/scripts/pkg-stats: add support for reporting stale CVE entries

The NVD database contains some CPEs that are wrongly not associated
with any version number. They are for example sometimes associated
with very old CVEs.
Those CPEs are annoying, because they pollute our pkg-stat CVE results
with CVE entries which actually don't affect us.

The proper way to solve it is, and should remain, to fix the NVD
database by reporting these issues. Having to deal with a lot of
CVEs/CPEs, the NVD database is however slow to be updated.

To reduce the noise in our pkg-stats results in the meantime, one
possibility is to add <PKG_IGNORE_CVES> entries for those CVEs.  This
however comes with the downside that even once the NVD database gets
fixed, those ignored entries risk remaining in Buildroot forever
because they are undetected.

This commit tries to address this downside by checking for and
reporting CVEs that are ignored in Buildroot, but where the
NVD reports our package version as unaffected. Those CVEs will appear
in the 'CVEs Ignored' column as '(stale)', and the cell will be
colored the same way warnings are. This should allow us to detect and
remove those entries.

It can be tested for example by adding the following variable to the
apache package (for a CVE that was recently fixed in the NVD database):
APACHE_IGNORE_CVES = CVE-1999-0236

Signed-off-by: Raphaël Mélotte <raphael.melotte@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 56ea5a02268631f2ea679c067e9b0ec94e0e512e)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

support/scripts/cve.py

@@ -184,13 +184,11 @@ class CVE:
         """The set of CPE products referred by this CVE definition"""
         return set(cpe_product(p['id']) for p in self.each_cpe())
 
-    def affects(self, name, version, cve_ignore_list, cpeid=None):
+    def affects(self, name, version, cpeid=None):
         """
         True if the Buildroot Package object passed as argument is affected
         by this CVE.
         """
-        if self.identifier in cve_ignore_list:
-            return self.CVE_DOESNT_AFFECT
 
         pkg_version = distutils.version.LooseVersion(version)
         if not hasattr(pkg_version, "version"):

support/scripts/pkg-stats

@@ -122,6 +122,7 @@ class Package:
         self.cves = list()
         self.ignored_cves = list()
         self.unsure_cves = list()
+        self.stale_cve_ignores = list()
         self.latest_version = {'status': RM_API_STATUS_ERROR, 'version': None, 'id': None}
         self.status = {}
 
@@ -638,7 +639,18 @@ def check_package_cve_affects(cve, cpe_product_pkgs):
         if product not in cpe_product_pkgs:
             continue
         for pkg in cpe_product_pkgs[product]:
-            cve_status = cve.affects(pkg.name, pkg.current_version, pkg.ignored_cves, pkg.cpeid)
+            cve_status = cve.affects(pkg.name, pkg.current_version, pkg.cpeid)
+
+            if cve.identifier in pkg.ignored_cves:
+                if cve_status == cve.CVE_DOESNT_AFFECT:
+                    # We have an ignore entry for a CVE which is
+                    # already reported as 'not affected'. This might
+                    # happen for example when the NVD database doesn't
+                    # initially include version numbers for a CPE, and
+                    # later fixes it. Store it so that we can report
+                    # it.
+                    pkg.stale_cve_ignores.append(cve.identifier)
+                cve_status = cve.CVE_DOESNT_AFFECT
             if cve_status == cve.CVE_AFFECTS:
                 pkg.cves.append(cve.identifier)
             elif cve_status == cve.CVE_UNKNOWN:
@@ -670,6 +682,8 @@ def check_package_cves(nvd_path, packages):
         if 'cve' not in pkg.status:
             if pkg.cves or pkg.unsure_cves:
                 pkg.status['cve'] = ("error", "affected by CVEs")
+            elif pkg.stale_cve_ignores:
+                pkg.status['cve'] = ("warning", "has stale CVE ignores")
             else:
                 pkg.status['cve'] = ("ok", "not affected by CVEs")
 
@@ -712,10 +726,13 @@ def calculate_stats(packages):
         stats["patches"] += pkg.patch_count
         stats["total-cves"] += len(pkg.cves)
         stats["total-unsure-cves"] += len(pkg.unsure_cves)
+        stats["total-stale-cve-ignores"] += len(pkg.stale_cve_ignores)
         if len(pkg.cves) != 0:
             stats["pkg-cves"] += 1
         if len(pkg.unsure_cves) != 0:
             stats["pkg-unsure-cves"] += 1
+        if len(pkg.stale_cve_ignores) != 0:
+            stats["pkg-stale-cve-ignores"] += 1
         if pkg.cpeid:
             stats["cpe-id"] += 1
         else:
@@ -867,7 +884,7 @@ function expandField(fieldId){
  .wrong, .lotsofpatches, .invalid_url, .version-needs-update, .cpe-nok, .cve-nok {
    background: #ff9a69;
  }
- .somepatches, .somewarnings, .missing_url, .version-unknown, .cpe-unknown, .cve-unknown {
+ .somepatches, .somewarnings, .missing_url, .version-unknown, .cpe-unknown, .cve-unknown, .cve-stale {
    background: #ffd870;
  }
  .cve_ignored, .version-error {
@@ -1080,10 +1097,17 @@ def dump_html_pkg(f, pkg):
     div_class = ["centered data ignored_cves"]
     div_class.append(f'_{pkg_css_class}')
     if pkg.ignored_cves:
-        div_class.append("cve_ignored")
+        if pkg.stale_cve_ignores:
+            div_class.append("cve-stale")
+        else:
+            div_class.append("cve_ignored")
     f.write(f'  <div id="{data_field_id}" class="{" ".join(div_class)}">\n')
     for ignored_cve in pkg.ignored_cves:
-        f.write(f'    <a href="https://security-tracker.debian.org/tracker/{ignored_cve}">{ignored_cve}</a><br/>\n')
+        if ignored_cve in pkg.stale_cve_ignores:
+            f.write(f"""    <a href="https://security-tracker.debian.org/tracker/{ignored_cve}">{ignored_cve}"""
+                    """ <i>(stale)</i></a><br/>\n""")
+        else:
+            f.write(f'    <a href="https://security-tracker.debian.org/tracker/{ignored_cve}">{ignored_cve}</a><br/>\n')
     f.write("  </div>\n")
 
     # CPE ID
@@ -1193,6 +1217,10 @@ def dump_html_stats(f, stats):
             stats["pkg-unsure-cves"])
     f.write('<div class="data">Total number of unsure CVEs affecting all packages</div><div class="data">%s</div>\n' %
             stats["total-unsure-cves"])
+    f.write('<div class="data">Packages with stale CVE ignores</div><div class="data">%s</div>\n' %
+            stats["pkg-stale-cve-ignores"])
+    f.write('<div class="data">Total number of stale CVE ignores affecting all packages</div><div class="data">%s</div>\n' %
+            stats["total-stale-cve-ignores"])
     f.write('<div class="data">Packages with CPE ID</div><div class="data">%s</div>\n' %
             stats["cpe-id"])
     f.write('<div class="data">Packages without CPE ID</div><div class="data">%s</div>\n' %