asn: reject trailing bytes after the last PolicyInformation in certificatePolicies

Author: gasbytes

tests/api/test_asn.c

@@ -1603,6 +1603,34 @@ int test_DecodeCertExtensions_empty_certpol(void)
     return EXPECT_RESULT();
 }
 
+/* Trailing bytes after the last PolicyInformation must be rejected rather than
+ * skipped. */
+int test_DecodeCertExtensions_certpol_trailing_junk(void)
+{
+    EXPECT_DECLS;
+#if (defined(WOLFSSL_SEP) || defined(WOLFSSL_CERT_EXT)) && \
+    !defined(NO_CERTS) && !defined(NO_ASN)
+    /* One valid PolicyInformation followed by two bytes that are not one. */
+    static const byte trailingJunk[] = {
+        0x30, 0x09,                          /* certificatePolicies SEQUENCE */
+            0x30, 0x05,                      /* PolicyInformation SEQUENCE */
+                0x06, 0x03, 0x2A, 0x03, 0x04,/* policyIdentifier OID 1.2.3.4 */
+            0x00, 0x00                       /* trailing junk */
+    };
+    DecodedCert cert;
+    int isUnknown = 0;
+
+    wc_InitDecodedCert(&cert, trailingJunk, (word32)sizeof(trailingJunk), NULL);
+
+    ExpectIntEQ(DecodeExtensionType(trailingJunk, (word32)sizeof(trailingJunk),
+        CERT_POLICY_OID, 0, &cert, &isUnknown),
+        WC_NO_ERR_TRACE(ASN_PARSE_E));
+
+    wc_FreeDecodedCert(&cert);
+#endif
+    return EXPECT_RESULT();
+}
+
 int test_ParseCert_SM3wSM2_short_pubkey(void)
 {
     EXPECT_DECLS;

tests/api/test_asn.h

@@ -37,6 +37,7 @@ int test_SerialNumber0_RootCA(void);
 int test_DecodeAltNames_length_underflow(void);
 int test_DecodeCertExtensions_dup_certpol(void);
 int test_DecodeCertExtensions_empty_certpol(void);
+int test_DecodeCertExtensions_certpol_trailing_junk(void);
 int test_ParseCert_SM3wSM2_short_pubkey(void);
 int test_ParseCert_dnBufferBoundary(void);
 int test_wc_DecodeObjectId(void);
@@ -63,6 +64,7 @@ int test_wc_AsnFeatureCoverage(void);
     TEST_DECL_GROUP("asn", test_DecodeAltNames_length_underflow),   \
     TEST_DECL_GROUP("asn", test_DecodeCertExtensions_dup_certpol),  \
     TEST_DECL_GROUP("asn", test_DecodeCertExtensions_empty_certpol), \
+    TEST_DECL_GROUP("asn", test_DecodeCertExtensions_certpol_trailing_junk), \
     TEST_DECL_GROUP("asn", test_ParseCert_SM3wSM2_short_pubkey),    \
     TEST_DECL_GROUP("asn", test_ParseCert_dnBufferBoundary),        \
     TEST_DECL_GROUP("asn", test_wc_DecodeObjectId),                 \

wolfcrypt/src/asn.c

@@ -21487,8 +21487,9 @@ static int DecodeCertPolicy(const byte* input, word32 sz, DecodedCert* cert)
         }
     }
 
-    /* Unwrap certificatePolicies */
-    while ((ret == 0) && ((int)idx < total_length)
+    /* Unwrap certificatePolicies. idx is an offset into input, so it is bound
+     * by sz. */
+    while ((ret == 0) && (idx < sz)
     #if defined(WOLFSSL_CERT_EXT)
         && (cert->extCertPoliciesNb < MAX_CERTPOL_NB)
     #endif