[PATCH v2 14/18] cve_check: Escape special characters in CPE 2.3 formatted strings

[Stefano Tondo <stondo@gmail.com>]

From: Stefano Tondo <stefano.tondo.ext@siemens.com>

CPE 2.3 formatted string binding (cpe:2.3:...) requires backslash escaping
for special meta-characters according to NISTIR 7695. Characters like '++'
and ':' in product names must be properly escaped to pass SBOM validation.

The CPE 2.3 specification defines two bindings:
- URI binding (cpe:/...) uses percent-encoding
- Formatted string binding (cpe:2.3:...) uses backslash escaping

This patch implements the formatted string binding properly by escaping
only the required meta-characters with backslash:
- Backslash (\) -> \\
- Question mark (?) -> \?
- Asterisk (*) -> \*
- Colon (:) -> \:
- Plus (+) -> \+ (required by some SBOM validators)

All other characters including -, etc. are kept as-is without encoding.

Example CPE identifiers:
- cpe:2.3:*:*:crow:1.0+x:*:*:*:*:*:*:*
- cpe:2.3:*:*:sdbus-c++:2.2.1:*:*:*:*:*:*:*

Signed-off-by: Stefano Tondo <stefano.tondo.ext@siemens.com>
---
 meta/lib/oe/cve_check.py | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/meta/lib/oe/cve_check.py b/meta/lib/oe/cve_check.py
index ae194f27cf..fa210e2037 100644
--- a/meta/lib/oe/cve_check.py
+++ b/meta/lib/oe/cve_check.py
@@ -205,6 +205,34 @@ def get_patched_cves(d):
     return patched_cves
 
 
+def cpe_escape(value):
+    r"""
+    Escape special characters for CPE 2.3 formatted string binding.
+
+    CPE 2.3 formatted string binding (cpe:2.3:...) uses backslash escaping
+    for special meta-characters, NOT percent-encoding. Percent-encoding is
+    only used in the URI binding (cpe:/...).
+
+    According to NISTIR 7695, these characters need escaping:
+    - Backslash (\) -> \\
+    - Question mark (?) -> \?
+    - Asterisk (*) -> \*
+    - Colon (:) -> \:
+    - Plus (+) -> \+ (required by some SBOM validators)
+    """
+    if not value:
+        return value
+
+    # Escape special meta-characters for CPE 2.3 formatted string binding
+    # Order matters: escape backslash first to avoid double-escaping
+    result = value.replace('\\', '\\\\')
+    result = result.replace('?', '\\?')
+    result = result.replace('*', '\\*')
+    result = result.replace(':', '\\:')
+    result = result.replace('+', '\\+')
+
+    return result
+
 def get_cpe_ids(cve_product, version):
     """
     Get list of CPE identifiers for the given product and version
@@ -221,7 +249,14 @@ def get_cpe_ids(cve_product, version):
         else:
             vendor = "*"
 
-        cpe_id = 'cpe:2.3:*:{}:{}:{}:*:*:*:*:*:*:*'.format(vendor, product, version)
+        # Encode special characters per CPE 2.3 specification
+        encoded_vendor = cpe_escape(vendor) if vendor != "*" else vendor
+        encoded_product = cpe_escape(product)
+        encoded_version = cpe_escape(version)
+
+        cpe_id = 'cpe:2.3:*:{}:{}:{}:*:*:*:*:*:*:*'.format(
+            encoded_vendor, encoded_product, encoded_version
+        )
         cpe_ids.append(cpe_id)
 
     return cpe_ids
-- 
2.53.0