Skoll review

Author: jackctj117

certs/test-serial0/generate_certs.sh

@@ -11,6 +11,8 @@
 #   ee_serial0.pem                           - EE cert with serial 0 (rejected)
 #   ee_normal.pem                            - Normal EE cert (serial 100)
 #   selfsigned_nonca_serial0.pem             - Self-signed non-CA, serial 0
+#   intermediate_serial0.pem                 - Intermediate CA, serial 0
+#                                              (CA:TRUE but issuer != subject)
 
 set -e
 
@@ -23,7 +25,7 @@ echo "==================================================="
 
 # 1. Create Root CA with serial number 0
 echo ""
-echo "[1/4] Creating Root CA with serial number 0..."
+echo "[1/5] Creating Root CA with serial number 0..."
 openssl req -x509 -newkey rsa:2048 -keyout root_serial0_key.pem -out root_serial0.pem \
     -days 7300 -nodes -subj "/CN=Test Root CA Serial 0/O=wolfSSL Test/C=US" \
     -set_serial 0 \
@@ -35,7 +37,7 @@ openssl x509 -in root_serial0.pem -noout -serial
 
 # 2. Create end-entity cert with serial 0 signed by root_serial0
 echo ""
-echo "[2/4] Creating end-entity certificate with serial number 0..."
+echo "[2/5] Creating end-entity certificate with serial number 0..."
 openssl req -newkey rsa:2048 -keyout ee_serial0_key.tmp -out ee_serial0.csr.tmp -nodes \
     -subj "/CN=End Entity Serial 0/O=wolfSSL Test/C=US"
 
@@ -52,7 +54,7 @@ openssl x509 -in ee_serial0.pem -noout -serial
 
 # 3. Create normal end-entity cert signed by root CA with serial 0
 echo ""
-echo "[3/4] Creating normal end-entity certificate (signed by serial 0 root)..."
+echo "[3/5] Creating normal end-entity certificate (signed by serial 0 root)..."
 openssl req -newkey rsa:2048 -keyout ee_normal_key.tmp -out ee_normal.csr.tmp -nodes \
     -subj "/CN=End Entity Normal/O=wolfSSL Test/C=US"
 
@@ -69,7 +71,7 @@ openssl x509 -in ee_normal.pem -noout -serial
 
 # 4. Create self-signed non-CA certificate with serial 0
 echo ""
-echo "[4/4] Creating self-signed non-CA certificate with serial number 0..."
+echo "[4/5] Creating self-signed non-CA certificate with serial number 0..."
 openssl req -x509 -newkey rsa:2048 -keyout selfsigned_nonca_serial0_key.tmp \
     -out selfsigned_nonca_serial0.pem -days 3650 -nodes \
     -subj "/CN=Self-Signed Non-CA Serial 0/O=wolfSSL Test/C=US" \
@@ -82,6 +84,25 @@ rm -f selfsigned_nonca_serial0_key.tmp
 echo "   Self-signed non-CA cert serial number:"
 openssl x509 -in selfsigned_nonca_serial0.pem -noout -serial
 
+# 5. Create intermediate CA cert with serial 0, signed by root_serial0
+#    (CA:TRUE but issuer != subject, so cert->selfSigned will be 0).
+echo ""
+echo "[5/5] Creating intermediate CA certificate with serial number 0..."
+openssl req -newkey rsa:2048 -keyout intermediate_serial0_key.tmp \
+    -out intermediate_serial0.csr.tmp -nodes \
+    -subj "/CN=Intermediate CA Serial 0/O=wolfSSL Test/C=US"
+
+openssl x509 -req -in intermediate_serial0.csr.tmp \
+    -CA root_serial0.pem -CAkey root_serial0_key.pem \
+    -out intermediate_serial0.pem -days 3650 -set_serial 0 \
+    -extfile <(echo "basicConstraints=critical,CA:TRUE
+keyUsage=critical,keyCertSign,cRLSign")
+
+rm -f intermediate_serial0_key.tmp intermediate_serial0.csr.tmp
+
+echo "   Intermediate CA cert serial number:"
+openssl x509 -in intermediate_serial0.pem -noout -serial
+
 echo ""
 echo "==================================================="
 echo "Certificate generation complete!"

certs/test-serial0/include.am

@@ -7,5 +7,6 @@ EXTRA_DIST += certs/test-serial0/generate_certs.sh \
              certs/test-serial0/root_serial0_key.pem \
              certs/test-serial0/ee_serial0.pem \
              certs/test-serial0/ee_normal.pem \
-             certs/test-serial0/selfsigned_nonca_serial0.pem
+             certs/test-serial0/selfsigned_nonca_serial0.pem \
+             certs/test-serial0/intermediate_serial0.pem
 

certs/test-serial0/intermediate_serial0.pem

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

tests/api.c

@@ -21386,67 +21386,69 @@ static int test_MakeCertWithPathLen(void)
     return EXPECT_RESULT();
 }
 
-static int test_MakeCertWith0Ser(void)
+/* Exhaustive matrix coverage of the serial-0 predicate in
+ * ParseCertRelative (asn.c). Inputs are openssl-generated PEM fixtures
+ * under certs/test-serial0/ — no cert-under-test data is generated by
+ * wolfSSL, so the test cannot pass for the wrong reason if wc_MakeCert
+ * encoding ever drifts.
+ *
+ * Predicate exempts only (CA_TYPE|TRUSTED_PEER_TYPE) && isCA && selfSigned.
+ *
+ *   Fixture                          isCA selfSigned CERT_TYPE CA_TYPE
+ *   root_serial0.pem                 1    1          reject    accept
+ *   intermediate_serial0.pem         1    0          reject    reject
+ *   selfsigned_nonca_serial0.pem     0    1          reject    reject
+ *   ee_serial0.pem                   0    0          reject    reject
+ */
+static int test_ParseSerial0FixtureMatrix(void)
 {
     EXPECT_DECLS;
-#if defined(WOLFSSL_CERT_REQ) && !defined(NO_ASN_TIME) && \
-    defined(WOLFSSL_CERT_GEN) && !defined(NO_RSA) && \
-    defined(WOLFSSL_KEY_GEN) && defined(WOLFSSL_ASN_TEMPLATE)
-    Cert cert;
-    DecodedCert decodedCert;
-    byte der[FOURK_BUF];
-    int derSize = 0;
-    WC_RNG rng;
-    RsaKey key;
-    int ret;
-
-    XMEMSET(&rng, 0, sizeof(WC_RNG));
-    XMEMSET(&key, 0, sizeof(RsaKey));
-    XMEMSET(&cert, 0, sizeof(Cert));
-    XMEMSET(&decodedCert, 0, sizeof(DecodedCert));
-
-    ExpectIntEQ(wc_InitRng(&rng), 0);
-    ExpectIntEQ(wc_InitRsaKey(&key, NULL), 0);
-    ExpectIntEQ(wc_MakeRsaKey(&key, 2048, WC_RSA_EXPONENT, &rng), 0);
-    ExpectIntEQ(wc_InitCert(&cert), 0);
-
-    (void)XSTRNCPY(cert.subject.country, "US", CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.state, "state", CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.locality, "Bozeman", CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.org, "yourOrgNameHere", CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.unit, "yourUnitNameHere", CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.commonName, "www.yourDomain.com",
-        CTC_NAME_SIZE);
-    (void)XSTRNCPY(cert.subject.email, "yourEmail@yourDomain.com",
-        CTC_NAME_SIZE);
-
-    cert.selfSigned = 1;
-    cert.isCA       = 0;
-    cert.sigType    = CTC_SHA256wRSA;
+#if !defined(NO_CERTS) && !defined(NO_FILESYSTEM) && \
+    defined(WOLFSSL_PEM_TO_DER) && !defined(WOLFSSL_NO_PEM) && \
+    !defined(WOLFSSL_NO_ASN_STRICT) && !defined(WOLFSSL_PYTHON) && \
+    !defined(WOLFSSL_ASN_ALLOW_0_SERIAL)
+    struct {
+        const char* path;
+        int  expectedCertType; /* expected wc_ParseCert(..., CERT_TYPE) */
+        int  expectedCaType;   /* expected wc_ParseCert(..., CA_TYPE) */
+    } cases[] = {
+        { "./certs/test-serial0/root_serial0.pem",
+            WC_NO_ERR_TRACE(ASN_PARSE_E), 0 },
+        { "./certs/test-serial0/intermediate_serial0.pem",
+            WC_NO_ERR_TRACE(ASN_PARSE_E), WC_NO_ERR_TRACE(ASN_PARSE_E) },
+        { "./certs/test-serial0/selfsigned_nonca_serial0.pem",
+            WC_NO_ERR_TRACE(ASN_PARSE_E), WC_NO_ERR_TRACE(ASN_PARSE_E) },
+        { "./certs/test-serial0/ee_serial0.pem",
+            WC_NO_ERR_TRACE(ASN_PARSE_E), WC_NO_ERR_TRACE(ASN_PARSE_E) },
+    };
+    size_t i;
 
-    /* set serial number to 0 */
-    cert.serialSz  = 1;
-    cert.serial[0] = 0;
+    for (i = 0; i < sizeof(cases) / sizeof(cases[0]); ++i) {
+        byte*  pemBuf = NULL;
+        size_t pemSz  = 0;
+        byte*  derBuf = NULL;
+        int    derSz  = 0;
+        DecodedCert dc;
 
-    ExpectIntGE(wc_MakeCert(&cert, der, FOURK_BUF, &key, NULL, &rng), 0);
-    ExpectIntGE(derSize = wc_SignCert(cert.bodySz, cert.sigType, der,
-        FOURK_BUF, &key, NULL, &rng), 0);
+        ExpectIntEQ(load_file(cases[i].path, &pemBuf, &pemSz), 0);
+        ExpectNotNull(derBuf = (byte*)XMALLOC(pemSz, NULL,
+            DYNAMIC_TYPE_TMP_BUFFER));
+        ExpectIntGE(derSz = wc_CertPemToDer(pemBuf, (int)pemSz, derBuf,
+            (int)pemSz, CERT_TYPE), 0);
 
-    wc_InitDecodedCert(&decodedCert, der, (word32)derSize, NULL);
+        wc_InitDecodedCert(&dc, derBuf, (word32)derSz, NULL);
+        ExpectIntEQ(wc_ParseCert(&dc, CERT_TYPE, NO_VERIFY, NULL),
+            cases[i].expectedCertType);
+        wc_FreeDecodedCert(&dc);
 
-#if !defined(WOLFSSL_NO_ASN_STRICT) && !defined(WOLFSSL_PYTHON) && \
-    !defined(WOLFSSL_ASN_ALLOW_0_SERIAL)
-    ExpectIntEQ(wc_ParseCert(&decodedCert, CERT_TYPE, NO_VERIFY, NULL),
-        WC_NO_ERR_TRACE(ASN_PARSE_E));
-#else
-    ExpectIntEQ(wc_ParseCert(&decodedCert, CERT_TYPE, NO_VERIFY, NULL), 0);
-#endif
+        wc_InitDecodedCert(&dc, derBuf, (word32)derSz, NULL);
+        ExpectIntEQ(wc_ParseCert(&dc, CA_TYPE, NO_VERIFY, NULL),
+            cases[i].expectedCaType);
+        wc_FreeDecodedCert(&dc);
 
-    wc_FreeDecodedCert(&decodedCert);
-    ret = wc_FreeRsaKey(&key);
-    ExpectIntEQ(ret, 0);
-    ret = wc_FreeRng(&rng);
-    ExpectIntEQ(ret, 0);
+        XFREE(derBuf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
+        XFREE(pemBuf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
+    }
 #endif
     return EXPECT_RESULT();
 }
@@ -34536,7 +34538,7 @@ TEST_CASE testCases[] = {
     TEST_DECL(test_wc_ParseCert),
     TEST_DECL(test_wc_ParseCert_Error),
     TEST_DECL(test_MakeCertWithPathLen),
-    TEST_DECL(test_MakeCertWith0Ser),
+    TEST_DECL(test_ParseSerial0FixtureMatrix),
     TEST_DECL(test_MakeCertWithCaFalse),
 #ifdef WOLFSSL_CERT_SIGN_CB
     TEST_DECL(test_wc_SignCert_cb),

tests/api/test_asn.c

@@ -1073,9 +1073,6 @@ int test_SerialNumber0_RootCA(void)
         wolfSSL_CertManagerFree(cm);
         cm = NULL;
     }
-    /* Balance the wolfSSL_Init refcount incremented by internal
-     * wolfSSL_CTX_new_ex calls in CertManagerLoadCA/Verify. */
-    wolfSSL_Cleanup();
 
     /* Test 4: Self-signed non-CA certificate with serial 0 should be rejected */
     ExpectNotNull(cm = wolfSSL_CertManagerNew());
@@ -1086,7 +1083,21 @@ int test_SerialNumber0_RootCA(void)
         wolfSSL_CertManagerFree(cm);
         cm = NULL;
     }
-    wolfSSL_Cleanup();
+
+    /* Test 5: Intermediate CA (CA:TRUE but issuer != subject) with serial 0
+     * must be rejected when loaded as CA_TYPE. Exercises the selfSigned
+     * half of the ParseCertRelative exemption predicate. */
+    {
+        const char* intermediateSerial0File =
+            "./certs/test-serial0/intermediate_serial0.pem";
+        ExpectNotNull(cm = wolfSSL_CertManagerNew());
+        ExpectIntNE(wolfSSL_CertManagerLoadCA(cm, intermediateSerial0File,
+                    NULL), WOLFSSL_SUCCESS);
+        if (cm != NULL) {
+            wolfSSL_CertManagerFree(cm);
+            cm = NULL;
+        }
+    }
 #endif /* !WOLFSSL_NO_ASN_STRICT && !WOLFSSL_PYTHON &&
           !WOLFSSL_ASN_ALLOW_0_SERIAL &&
           !WOLFSSL_TEST_APPLE_NATIVE_CERT_VALIDATION */

wolfcrypt/src/asn.c

@@ -20633,6 +20633,13 @@ static int DecodeCertInternal(DecodedCert* cert, int verify, int* criticalExt,
         ret = badDate;
     }
 
+    /* Note: serial-0 rejection is performed in ParseCertRelative (after
+     * basicConstraints has been parsed and isCA is authoritative), not
+     * here. Checking isCA at this point would fail-open on a forged
+     * isCA flag. Callers that invoke DecodeCert/DecodeToKey/wc_GetPubX509
+     * directly are pubkey-extraction paths and do not make trust
+     * decisions; trust-bearing flows go through ParseCertRelative. */
+
     return ret;
 }
 
@@ -22035,18 +22042,28 @@ int ParseCertRelative(DecodedCert* cert, int type, int verify, void* cm,
 
 #if !defined(WOLFSSL_NO_ASN_STRICT) && !defined(WOLFSSL_PYTHON) && \
     !defined(WOLFSSL_ASN_ALLOW_0_SERIAL)
-        /* Check for serial number of 0. RFC 5280 section 4.1.2.2 requires
-         * positive serial numbers. However, allow zero for self-signed CA
-         * certificates (root CAs) being loaded as trust anchors since they
-         * are explicitly trusted and some legacy root CAs in real-world
-         * trust stores have serial number 0. */
+        /* RFC 5280 section 4.1.2.2 requires conforming CAs to issue
+         * positive serial numbers; the same section notes that verifiers
+         * SHOULD gracefully handle non-conforming certs with zero or
+         * negative serials. wolfSSL's policy is to reject as a security
+         * guard, with an exemption for self-signed CA certs loaded as
+         * explicitly-trusted anchors (some legacy real-world roots have
+         * serial 0).
+         *
+         * Note: cert->selfSigned is a subject/issuer name-hash compare
+         * (see DecodeCertInternal where it's set), not a validated
+         * self-signature. That is acceptable here because the trust
+         * decision is user-driven via CertManagerLoadCA; this check is
+         * only a structural sanity guard. */
         if ((ret == 0) && (cert->serialSz == 1) && (cert->serial[0] == 0)) {
-            if (!((type == CA_TYPE || type == TRUSTED_PEER_TYPE) &&
-                  cert->isCA && cert->selfSigned)
-#ifdef WOLFSSL_CERT_REQ
-                && !cert->isCSR
-#endif
-            ) {
+            int isTrustAnchorLoad =
+                (type == CA_TYPE || type == TRUSTED_PEER_TYPE)
+                && cert->isCA && cert->selfSigned;
+            int isCsr = 0;
+        #ifdef WOLFSSL_CERT_REQ
+            isCsr = cert->isCSR;
+        #endif
+            if (!isTrustAnchorLoad && !isCsr) {
                 WOLFSSL_MSG("Error serial number of 0 for non-root certificate");
                 return ASN_PARSE_E;
             }