Make CPE matching case insensitive

According to

Common Platform Enumeration: Naming Specification Version 2.3
Section 2.3
and
Common Platform Enumeration: Name Matching Specification Version 2.3
Section 7.3 and 6.1.3.2

CPE attributes should be lowercased before comparing them.

In practice, all CPEs in the CVE Database are in lowercase,
that shouldn't be a problem, but comparing with user input
(like CPE coming from an SBOM) should work according to the
specification.

cpematcher/core.py

@@ -77,6 +77,7 @@ def matches(self, other: Self) -> bool:
 
     @staticmethod
     def _glob_equal(value1: str, value2: str) -> bool:
+        value1, value2 = value1.lower(), value2.lower()
         # Depending on the order, fnmatch.fnmatch could return False if wildcard
         # is the first value. As wildcard should always return True in any case,
         # we reorder the arguments based on that.

cpematcher/version.py

@@ -2,8 +2,8 @@
 
 
 class Version:
-    def __init__(self, version: str):
-        self.version = version
+    def __init__(self, version: str | None):
+        self.version = version and version.lower()
 
     def __bool__(self):
         return bool(self.version)

tests/test_core.py

@@ -50,9 +50,21 @@ def test_matches_with_same_branch(self):
 
     def test_matches_with_exact_version(self):
         version_cpe = CPE("cpe:2.3:a:apache:activemq:4.1.1:*:*:*:*:*:*:*")
-
         assert version_cpe.matches(version_cpe)
 
+    def test_matches_case_insensitive(self):
+        cpe_str = "cpe:2.3:a:apache:activemq:4.1.1:*:*:*:*:*:*:*"
+        cpe = CPE(cpe_str)
+        upper_cpe = CPE(cpe_str.replace("apche", "APACHE"))
+        assert cpe.matches(upper_cpe)
+
+        cpe_alnum_version = (
+            "cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:*"
+        )
+        alnum_cpe = CPE(cpe_alnum_version)
+        cpe_alnum_upper = CPE(cpe_alnum_version.replace("r2:sp1", "R2:SP1"))
+        assert alnum_cpe.matches(cpe_alnum_upper)
+
     def test_matches_with_version_start_including(self):
         branch_cpe = CPE(self.template % "4.1.*", version_start_including="4.1.3")