Check keyUsage in SSL client and server

include/polarssl/ssl.h

@@ -1657,6 +1657,19 @@ static inline x509_crt *ssl_own_cert( ssl_context *ssl )
     return( ssl->handshake->key_cert == NULL ? NULL
             : ssl->handshake->key_cert->cert );
 }
+
+/*
+ * Check usage of a certificate wrt extensions:
+ * keyUsage, extendedKeyUsage (later), and nSCertType (later).
+ *
+ * Warning: cert_endpoint is the endpoint of the cert (ie, of our peer when we
+ * check a cert we received from them)!
+ *
+ * Return 0 if everything is OK, -1 if not.
+ */
+int ssl_check_cert_usage( const x509_crt *cert,
+                          const ssl_ciphersuite_t *ciphersuite,
+                          int cert_endpoint );
 #endif /* POLARSSL_X509_CRT_PARSE_C */
 
 /* constant-time buffer comparison */

library/ssl_srv.c

@@ -797,6 +797,20 @@ static int ssl_pick_cert( ssl_context *ssl,
         if( ! pk_can_do( cur->key, pk_alg ) )
             continue;
 
+        /*
+         * This avoids sending the client a cert it'll reject based on
+         * keyUsage or other extensions.
+         *
+         * It also allows the user to provision different certificates for
+         * different uses based on keyUsage, eg if they want to avoid signing
+         * and decrypting with the same RSA key.
+         */
+        if( ssl_check_cert_usage( cur->cert, ciphersuite_info,
+                                  SSL_IS_SERVER ) != 0 )
+        {
+            continue;
+        }
+
 #if defined(POLARSSL_ECDSA_C)
         if( pk_alg == POLARSSL_PK_ECDSA )
         {

library/ssl_tls.c

@@ -2699,6 +2699,9 @@ int ssl_parse_certificate( ssl_context *ssl )
             return( POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED );
         }
 
+        /*
+         * Main check: verify certificate
+         */
         ret = x509_crt_verify( ssl->session_negotiate->peer_cert,
                                ssl->ca_chain, ssl->ca_crl, ssl->peer_cn,
                               &ssl->session_negotiate->verify_result,
@@ -2708,21 +2711,35 @@ int ssl_parse_certificate( ssl_context *ssl )
         {
             SSL_DEBUG_RET( 1, "x509_verify_cert", ret );
         }
+
+        /*
+         * Secondary checks: always done, but change 'ret' only if it was 0
+         */
+
 #if defined(POLARSSL_SSL_SET_CURVES)
-        else
         {
-            pk_context *pk = &ssl->session_negotiate->peer_cert->pk;
+            const pk_context *pk = &ssl->session_negotiate->peer_cert->pk;
 
             /* If certificate uses an EC key, make sure the curve is OK */
             if( pk_can_do( pk, POLARSSL_PK_ECKEY ) &&
                 ! ssl_curve_is_acceptable( ssl, pk_ec( *pk )->grp.id ) )
             {
                 SSL_DEBUG_MSG( 1, ( "bad server certificate (EC key curve)" ) );
-                ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
+                if( ret == 0 )
+                    ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
             }
         }
 #endif
 
+        if( ssl_check_cert_usage( ssl->session_negotiate->peer_cert,
+                                  ciphersuite_info,
+                                  ! ssl->endpoint ) != 0 )
+        {
+            SSL_DEBUG_MSG( 1, ( "bad server certificate (usage ext.)" ) );
+            if( ret == 0 )
+                ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
+        }
+
         if( ssl->authmode != SSL_VERIFY_REQUIRED )
             ret = 0;
     }
@@ -4747,3 +4764,54 @@ int ssl_curve_is_acceptable( const ssl_context *ssl, ecp_group_id grp_id )
     return( 0 );
 }
 #endif
+
+int ssl_check_cert_usage( const x509_crt *cert,
+                          const ssl_ciphersuite_t *ciphersuite,
+                          int cert_endpoint )
+{
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+    int usage = 0;
+#endif
+
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+    if( cert_endpoint == SSL_IS_SERVER )
+    {
+        /* Server part of the key exchange */
+        switch( ciphersuite->key_exchange )
+        {
+            case POLARSSL_KEY_EXCHANGE_RSA:
+            case POLARSSL_KEY_EXCHANGE_RSA_PSK:
+                usage = KU_KEY_ENCIPHERMENT;
+                break;
+
+            case POLARSSL_KEY_EXCHANGE_DHE_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_ECDSA:
+                usage = KU_DIGITAL_SIGNATURE;
+                break;
+
+            case POLARSSL_KEY_EXCHANGE_ECDH_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDH_ECDSA:
+                usage = KU_KEY_AGREEMENT;
+                break;
+
+            /* Don't use default: we want warnings when adding new values */
+            case POLARSSL_KEY_EXCHANGE_NONE:
+            case POLARSSL_KEY_EXCHANGE_PSK:
+            case POLARSSL_KEY_EXCHANGE_DHE_PSK:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_PSK:
+                usage = 0;
+        }
+    }
+    else
+    {
+        /* Client auth: we only implement rsa_sign and ecdsa_sign for now */
+        usage = KU_DIGITAL_SIGNATURE;
+    }
+
+    if( x509_crt_check_key_usage( cert, usage ) != 0 )
+        return( -1 );
+#endif /* POLARSSL_X509_CHECK_KEY_USAGE */
+
+    return( 0 );
+}

tests/data_files/server2.ku-ds.crt

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIDijCCAnKgAwIBAgIBLDANBgkqhkiG9w0BAQUFADA7MQswCQYDVQQGEwJOTDER
+MA8GA1UEChMIUG9sYXJTU0wxGTAXBgNVBAMTEFBvbGFyU1NMIFRlc3QgQ0EwHhcN
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+-----END CERTIFICATE-----

tests/data_files/server2.ku-ds_ke.crt

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIDijCCAnKgAwIBAgIBMDANBgkqhkiG9w0BAQUFADA7MQswCQYDVQQGEwJOTDER
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+sYDyD/ZyIlavoPSEiD3LTT/Tp6BIpz+zb4WHOHLEvUCsZputqxPVcNoEAi9xuA==
+-----END CERTIFICATE-----

tests/data_files/server2.ku-ka.crt

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIDijCCAnKgAwIBAgIBKjANBgkqhkiG9w0BAQUFADA7MQswCQYDVQQGEwJOTDER
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+-----END CERTIFICATE-----

tests/data_files/server2.ku-ke.crt

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIDijCCAnKgAwIBAgIBKzANBgkqhkiG9w0BAQUFADA7MQswCQYDVQQGEwJOTDER
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+-----END CERTIFICATE-----

tests/data_files/server5.ku-ds.crt

@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----
+MIICLTCCAbKgAwIBAgIBLTAKBggqhkjOPQQDAjA+MQswCQYDVQQGEwJOTDERMA8G
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+-----END CERTIFICATE-----

tests/data_files/server5.ku-ka.crt

@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----
+MIICKzCCAbKgAwIBAgIBLjAKBggqhkjOPQQDAjA+MQswCQYDVQQGEwJOTDERMA8G
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+-----END CERTIFICATE-----

tests/data_files/server5.ku-ke.crt

@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----
+MIICKzCCAbKgAwIBAgIBLzAKBggqhkjOPQQDAjA+MQswCQYDVQQGEwJOTDERMA8G
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+-----END CERTIFICATE-----

tests/ssl-opt.sh

@@ -151,8 +151,9 @@ run_test() {
     CLI_EXIT=$?
     echo "EXIT: $CLI_EXIT" >> cli_out
 
+    # psk is usefull when server only has bad certs
     if is_polar "$SRV_CMD"; then
-        "$P_CLI" request_page=SERVERQUIT tickets=0 auth_mode=none \
+        "$P_CLI" request_page=SERVERQUIT tickets=0 auth_mode=none psk=abc123 \
             crt_file=data_files/cli2.crt key_file=data_files/cli2.key \
             >/dev/null
     else
@@ -980,6 +981,127 @@ run_test    "ALPN #6 (both, no common)" \
 
 fi
 
+# Tests for keyUsage in leaf certificates, part 1:
+# server-side certificate/suite selection
+
+run_test    "keyUsage srv #1 (RSA, digitalSignature -> ECDHE-RSA)" \
+            "$P_SRV key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ds.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDHE-RSA-WITH-"
+
+
+run_test    "keyUsage srv #2 (RSA, keyEncipherment -> RSA)" \
+            "$P_SRV key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ke.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-RSA-WITH-"
+
+# add psk to leave an option for client to send SERVERQUIT
+run_test    "keyUsage srv #3 (RSA, keyAgreement -> fail)" \
+            "$P_SRV psk=abc123 key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ka.crt" \
+            "$P_CLI psk=badbad" \
+            1 \
+            -C "Ciphersuite is "
+
+run_test    "keyUsage srv #4 (ECDSA, digitalSignature -> ECDHE-ECDSA)" \
+            "$P_SRV key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ds.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDHE-ECDSA-WITH-"
+
+
+run_test    "keyUsage srv #5 (ECDSA, keyAgreement -> ECDH-)" \
+            "$P_SRV key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ka.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDH-"
+
+# add psk to leave an option for client to send SERVERQUIT
+run_test    "keyUsage srv #6 (ECDSA, keyEncipherment -> fail)" \
+            "$P_SRV psk=abc123 key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ke.crt" \
+            "$P_CLI psk=badbad" \
+            1 \
+            -C "Ciphersuite is "
+
+# Tests for keyUsage in leaf certificates, part 2:
+# client-side checks
+
+run_test    "keyUsage cli #0 (reference, no extension)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.crt" \
+            "$P_CLI debug_level=2" \
+            0 \
+            -C "bad server certificate (usage ext.)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #1 (DigitalSignature+KeyEncipherment, RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds_ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad server certificate (usage ext.)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #2 (DigitalSignature+KeyEncipherment, DHE-RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds_ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad server certificate (usage ext.)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #3 (KeyEncipherment, RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad server certificate (usage ext.)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #4 (KeyEncipherment, DHE-RSA: fail)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            1 \
+            -c "bad server certificate (usage ext.)" \
+            -c "Processing of the Certificate handshake message failed" \
+            -C "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #5 (DigitalSignature, DHE-RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad server certificate (usage ext.)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #5 (DigitalSignature, RSA: fail)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            1 \
+            -c "bad server certificate (usage ext.)" \
+            -c "Processing of the Certificate handshake message failed" \
+            -C "Ciphersuite is TLS-"
+
 # Final report
 
 echo "------------------------------------------------------------------------"