Merge pull request #6869 from bigbrett/ios-ca-api

Add support for new Apple trust APIs with WOLFSSL_SYS_CA_CERTS

Author: dgarske

CMakeLists.txt

@@ -1724,21 +1724,23 @@ if(WOLFSSL_SYS_CA_CERTS)
         override_cache(WOLFSSL_SYS_CA_CERTS "no")
     elseif(APPLE)
         check_include_file("Security/SecTrustSettings.h" HAVE_SECURITY_SECTRUSTSETTINGS_H)
-        if(NOT HAVE_SECURITY_SECTRUSTSETTINGS_H)
-            message("Can't enable system CA certs without Security/SecTrustSettings.h.")
-            override_cache(WOLFSSL_SYS_CA_CERTS "no")
-        else()
+        check_include_file("Security/SecCertificate.h" HAVE_SECURITY_SECCERTIFICATE_H)
+        check_include_file("Security/SecTrust.h" HAVE_SECURITY_SECTRUST_H)
+        check_include_file("Security/SecPolicy.h" HAVE_SECURITY_SECPOLICY_H)
+        if(HAVE_SECURITY_SECTRUSTSETTINGS_H OR (HAVE_SECURITY_SECCERTIFICATE_H
+                                                AND HAVE_SECURITY_SECTRUST_H
+                                                AND HAVE_SECURITY_SECPOLICY_H))
             find_library(CORE_FOUNDATION_FRAMEWORK CoreFoundation)
             if(NOT CORE_FOUNDATION_FRAMEWORK)
-                message("Can't enable system CA certs without CoreFoundation framework.")
-                override_cache(WOLFSSL_SYS_CA_CERTS "no")
+                message(FATAL_ERROR "Can't enable system CA certs without CoreFoundation framework.")
             else()
                 find_library(SECURITY_FRAMEWORK Security)
                 if(NOT SECURITY_FRAMEWORK)
-                    message("Can't enable system CA certs without Security framework.")
-                    override_cache(WOLFSSL_SYS_CA_CERTS "no")
+                    message(FATAL_ERROR "Can't enable system CA certs without Security framework.")
                 endif()
             endif()
+        else()
+            message(FATAL_ERROR "Can't enable system CA certs without Apple Security.framework headers.")
         endif()
     endif()
 

configure.ac

@@ -8351,14 +8351,24 @@ then
 
     case $host_os in
         *darwin*)
-            AC_CHECK_HEADERS([Security/SecTrustSettings.h],
+            # Creates the HAVE_SECURITY_SECXXX_H macros in config.h
+            AC_CHECK_HEADERS([Security/SecTrustSettings.h])
+            AC_CHECK_HEADERS([Security/SecCertificate.h])
+            AC_CHECK_HEADERS([Security/SecTrust.h])
+            AC_CHECK_HEADERS([Security/SecPolicy.h])
+            # Either Security/SecTrustSettings (for MacOS cert loading), or the
+            # trio of Security/SecCertificate.h, Security/SecTrust.h, and
+            # Security/SecPolicy.h (for native trust APIs other apple devices)
+            # must be present
+            AS_IF([test -n "$ac_cv_header_Security_SecTrustSettings_h" \
+                   || (test -n "$ac_cv_header_Security_SecCertificate_h" \
+                       && test -n "$ac_cv_header_Security_SecTrust_h" \
+                       && test -n "$ac_cv_header_Security_SecPolicy_h")],
                 [
-                    # For Mac we need these frameworks to load system CA certs
                     LDFLAGS="$LDFLAGS -framework CoreFoundation -framework Security"
                 ],
                 [
-                    AC_MSG_NOTICE([Can't enable system CA certs without Security/SecTrustSettings.h])
-                    ENABLED_SYS_CA_CERTS="no"
+                    AC_MSG_ERROR([Unable to find Apple Security.framework headers])
                 ]
             )
             ;;

doc/dox_comments/header_files/ssl.h

@@ -1236,7 +1236,9 @@ int wolfSSL_CTX_load_verify_locations_ex(WOLFSSL_CTX* ctx, const char* file,
 
     \brief This function returns a pointer to an array of strings representing
     directories wolfSSL will search for system CA certs when
-    wolfSSL_CTX_load_system_CA_certs is called.
+    wolfSSL_CTX_load_system_CA_certs is called. On systems that don't store
+    certificates in an accessible system directory (such as Apple platforms),
+    this function will always return NULL.
 
     \return Valid pointer on success.
     \return NULL pointer on failure.
@@ -1266,10 +1268,19 @@ const char** wolfSSL_get_system_CA_dirs(word32* num);
 /*!
     \ingroup CertsKeys
 
-    \brief This function attempts to load CA certificates into a WOLFSSL_CTX
-    from an OS-dependent CA certificate store. Loaded certificates will be
-    trusted. The platforms supported and tested are: Linux (Debian, Ubuntu, 
-    Gentoo, Fedora, RHEL), Windows 10/11, Android, Apple OS X and iOS.
+    \brief On most platforms (including Linux and Windows), this function
+    attempts to load CA certificates into a WOLFSSL_CTX from an OS-dependent
+    CA certificate store. Loaded certificates will be trusted.
+
+    On Apple platforms (excluding macOS), certificates can't be obtained from
+    the system, and therefore cannot be loaded into the wolfSSL certificate
+    manager. For these platforms, this function enables TLS connections bound to
+    the WOLFSSL_CTX to use the native system trust APIs to verify authenticity
+    of the peer certificate chain if the authenticity of the peer cannot first
+    be authenticated against certificates loaded by the user.
+
+    The platforms supported and tested are: Linux (Debian, Ubuntu,
+    Gentoo, Fedora, RHEL), Windows 10/11, Android, macOS, and iOS.
 
     \return WOLFSSL_SUCCESS on success.
     \return WOLFSSL_BAD_PATH if no system CA certs were loaded.

src/internal.c

@@ -217,6 +217,14 @@ WOLFSSL_CALLBACKS needs LARGE_STATIC_BUFFERS, please add LARGE_STATIC_BUFFERS
     static int _DtlsCheckWindow(WOLFSSL* ssl);
 #endif
 
+#if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+#include <Security/SecCertificate.h>
+#include <Security/SecTrust.h>
+#include <Security/SecPolicy.h>
+static int DoAppleNativeCertValidation(const WOLFSSL_BUFFER_INFO* certs,
+                                            int totalCerts);
+#endif /* #if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS) */
+
 #ifdef WOLFSSL_DTLS13
 #ifndef WOLFSSL_DTLS13_SEND_MOREACK_DEFAULT
 #define WOLFSSL_DTLS13_SEND_MOREACK_DEFAULT 0
@@ -271,6 +279,7 @@ static int SSL_hmac(WOLFSSL* ssl, byte* digest, const byte* in, word32 sz,
                        const unsigned char* secret, int secretSz, void* ctx);
 #endif
 
+
     /* Label string for client random. */
     #define SSC_CR      "CLIENT_RANDOM"
 
@@ -2426,6 +2435,11 @@ int InitSSL_Ctx(WOLFSSL_CTX* ctx, WOLFSSL_METHOD* method, void* heap)
     maxq10xx_SetupPkCallbacks(ctx, &method->version);
 #endif /* WOLFSSL_MAXQ10XX_TLS */
 
+#if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+    /* Should only be set when wolfSSL_CTX_load_system_CA_certs() is called */
+    ctx->doAppleNativeCertValidationFlag = 0;
+#endif /* defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS) */
+
     return ret;
 }
 
@@ -14205,6 +14219,24 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
                     }
                 #endif /* WOLFSSL_ALT_CERT_CHAINS */
 
+                #if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+                    /* If we are using native Apple CA validation, it is okay
+                     * for a CA cert to fail validation here, as we will verify
+                     * the entire chain when we hit the peer (leaf) cert */
+                    if (ssl->ctx->doAppleNativeCertValidationFlag) {
+                        WOLFSSL_MSG("Bypassing errors to allow for Apple native"
+                                    " CA validation");
+                        ret = 0; /* clear errors and continue */
+                        args->verifyErr = 0;
+                        #if defined(OPENSSL_EXTRA) \
+                            || defined(OPENSSL_EXTRA_X509_SMALL)
+                        ssl->peerVerifyRet = 0;
+                        #endif
+                        /* do not add to certificate manager */
+                        skipAddCA = 1;
+                    }
+                #endif /* defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS) */
+
                     /* Do verify callback */
                     ret = DoVerifyCallback(SSL_CM(ssl), ssl, ret, args);
                     if (ssl->options.verifyNone &&
@@ -14273,7 +14305,7 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
                     FreeDecodedCert(args->dCert);
                     args->dCertInit = 0;
                     args->count--;
-                } /* while (count > 0 && !args->haveTrustPeer) */
+                } /* while (count > 1 && !args->haveTrustPeer) */
             } /* if (count > 0) */
 
             /* Check for error */
@@ -14394,6 +14426,7 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
                 }
                 else {
                     WOLFSSL_MSG("Failed to verify Peer's cert");
+
                     #if defined(OPENSSL_EXTRA) || defined(OPENSSL_EXTRA_X509_SMALL)
                     if (ssl->peerVerifyRet == 0) { /* Return first cert error here */
                         if (ret == ASN_BEFORE_DATE_E) {
@@ -14411,6 +14444,7 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
                         }
                     }
                     #endif
+
                     if (ssl->verifyCallback) {
                         WOLFSSL_MSG(
                             "\tCallback override available, will continue");
@@ -14419,6 +14453,18 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
                         if (args->fatal)
                             DoCertFatalAlert(ssl, ret);
                     }
+                    #if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+                    /* Disregard failure to verify peer cert, as we will verify
+                     * the whole chain with the native API later */
+                    else if (ssl->ctx->doAppleNativeCertValidationFlag) {
+                        WOLFSSL_MSG("\tApple native CA validation override"
+                                    " available, will continue");
+                        /* check if fatal error */
+                        args->fatal = (args->verifyErr) ? 1 : 0;
+                        if (args->fatal)
+                            DoCertFatalAlert(ssl, ret);
+                    }
+                    #endif/*defined(__APPLE__)&& defined(WOLFSSL_SYS_CA_CERTS)*/
                     else {
                         WOLFSSL_MSG("\tNo callback override available, fatal");
                         args->fatal = 1;
@@ -15178,6 +15224,22 @@ int ProcessPeerCerts(WOLFSSL* ssl, byte* input, word32* inOutIdx,
             }
         #endif
 
+        #if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+            /* If we can't validate the peer cert chain against the CAs loaded
+             * into wolfSSL, try to validate against the system certificates
+             * using Apple's native trust APIs */
+            if ((ret != 0) && (ssl->ctx->doAppleNativeCertValidationFlag)) {
+                if (DoAppleNativeCertValidation(args->certs,
+                                                     args->totalCerts)) {
+                    WOLFSSL_MSG("Apple native cert chain validation SUCCESS");
+                    ret = 0;
+                }
+                else {
+                    WOLFSSL_MSG("Apple native cert chain validation FAIL");
+                }
+            }
+        #endif /* defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS) */
+
             /* Do verify callback */
             ret = DoVerifyCallback(SSL_CM(ssl), ssl, ret, args);
 
@@ -39353,6 +39415,139 @@ int wolfSSL_sk_BY_DIR_entry_push(WOLF_STACK_OF(WOLFSSL_BY_DIR_entry)* sk,
 
 #endif /* OPENSSL_ALL */
 
+#if defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS)
+
+/*
+ * Converts a DER formatted certificate to a SecCertificateRef
+ *
+ * @param derCert pointer to the DER formatted certificate
+ * @param derLen length of the DER formatted cert, in bytes
+ *
+ * @return The newly created SecCertificateRef. Must be freed by caller when
+ * no longer in use
+ */
+static SecCertificateRef ConvertToSecCertificateRef(const byte* derCert,
+                                                    int derLen)
+{
+    CFDataRef         derData = NULL;
+    SecCertificateRef secCert = NULL;
+
+    WOLFSSL_ENTER("ConvertToSecCertificateRef");
+
+    /* Create a CFDataRef from the DER encoded certificate */
+    derData = CFDataCreate(kCFAllocatorDefault, derCert, derLen);
+    if (!derData) {
+        WOLFSSL_MSG("Error: can't create CFDataRef object for DER cert");
+        goto cleanup;
+    }
+
+    /* Create a SecCertificateRef from the CFDataRef */
+    secCert = SecCertificateCreateWithData(kCFAllocatorDefault, derData);
+    if (!secCert) {
+        WOLFSSL_MSG("Error: can't create SecCertificateRef from CFDataRef");
+        goto cleanup;
+    }
+
+cleanup:
+    if (derData) {
+        CFRelease(derData);
+    }
+
+    WOLFSSL_LEAVE("ConvertToSecCertificateRef", !!secCert);
+
+    return secCert;
+}
+
+
+/*
+ * Validates a chain of certificates using the Apple system trust APIs
+ *
+ * @param certs pointer to the certificate chain to validate
+ * @param totalCerts the number of certificates in certs
+ *
+ * @return 1 if chain is valid and trusted
+ * @return 0 if chain is invalid or untrusted
+ *
+ * As of MacOS 14.0 we are still able to access system certificates and load
+ * them manually into wolfSSL. For other apple devices, apple has removed the
+ * ability to obtain certificates from the trust store, so we can't use
+ * wolfSSL's built-in certificate validation mechanisms anymore. We instead
+ * must call into the Security Framework APIs to authenticate peer certificates
+ */
+static int DoAppleNativeCertValidation(const WOLFSSL_BUFFER_INFO* certs,
+                                            int totalCerts)
+{
+    int i;
+    int ret;
+    OSStatus status;
+    CFMutableArrayRef certArray = NULL;
+    SecCertificateRef secCert   = NULL;
+    SecTrustRef       trust     = NULL;
+    SecPolicyRef      policy    = NULL ;
+
+    WOLFSSL_ENTER("DoAppleNativeCertValidation");
+
+    certArray = CFArrayCreateMutable(kCFAllocatorDefault,
+                                     totalCerts,
+                                     &kCFTypeArrayCallBacks);
+    if (!certArray) {
+        WOLFSSL_MSG("Error: can't allocate CFArray for certificates");
+        ret = 0;
+        goto cleanup;
+    }
+
+    for (i = 0; i < totalCerts; i++) {
+        secCert = ConvertToSecCertificateRef(certs[i].buffer, certs[i].length);
+        if (!secCert) {
+            WOLFSSL_MSG("Error: can't convert DER cert to SecCertificateRef");
+            ret = 0;
+            goto cleanup;
+        }
+        else {
+            CFArrayAppendValue(certArray, secCert);
+            /* Release, since the array now holds the reference */
+            CFRelease(secCert);
+        }
+    }
+
+    /* Create trust object for SecCertifiate Ref */
+    policy = SecPolicyCreateSSL(true, NULL);
+    status = SecTrustCreateWithCertificates(certArray, policy, &trust);
+    if (status != errSecSuccess) {
+        WOLFSSL_MSG_EX("Error creating trust object, "
+                       "SecTrustCreateWithCertificates returned %d",status);
+        ret = 0;
+        goto cleanup;
+    }
+
+    /* Evaluate the certificate's authenticity */
+    if (SecTrustEvaluateWithError(trust, NULL) == 1) {
+        WOLFSSL_MSG("Cert chain is trusted");
+        ret = 1;
+    }
+    else {
+        WOLFSSL_MSG("Cert chain trust evaluation failed"
+                    "SecTrustEvaluateWithError returned 0");
+        ret = 0;
+    }
+
+    /* Cleanup */
+cleanup:
+    if (certArray) {
+        CFRelease(certArray);
+    }
+    if (trust) {
+        CFRelease(trust);
+    }
+    if (policy) {
+        CFRelease(policy);
+    }
+
+    WOLFSSL_LEAVE("DoAppleNativeCertValidation", ret);
+
+    return ret;
+}
+#endif /* defined(__APPLE__) && defined(WOLFSSL_SYS_CA_CERTS) */
 
 #undef ERROR_OUT