Merge branch 'iotssl-1077-dos-crl'

Modifies the function mbedtls_x509_crl_parse() to ensure that a CRL in PEM
format with trailing characters after the footer does not result in the
execution of an infinite loop.

ChangeLog

@@ -3,6 +3,11 @@ mbed TLS ChangeLog (Sorted per branch, date)
 = mbed TLS 2.x.x branch released xxxx-xx-xx
 
 Security
+   * Fixed potential livelock during the parsing of a CRL in PEM format in
+     mbedtls_x509_crl_parse(). A string containing a CRL followed by trailing
+     characters after the footer could result in the execution of an infinite
+     loop. The issue can be triggered remotely. Found by Greg Zaverucha,
+     Microsoft.
    * Removed MD5 from the allowed hash algorithms for CertificateRequest and
      CertificateVerify messages, to prevent SLOTH attacks against TLS 1.2.
      Introduced by interoperability fix for #513.

library/x509_crl.c

@@ -530,7 +530,7 @@ int mbedtls_x509_crl_parse( mbedtls_x509_crl *chain, const unsigned char *buf, s
 
             mbedtls_pem_free( &pem );
         }
-        else if( ret != MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
+        else if( is_pem )
         {
             mbedtls_pem_free( &pem );
             return( ret );

tests/data_files/crl-malformed-trailing-spaces.pem

@@ -0,0 +1,20 @@
+-----BEGIN X509 CRL-----
+MIIBbzCB9gIBATAJBgcqhkjOPQQBMD4xCzAJBgNVBAYTAk5MMREwDwYDVQQKEwhQ
+b2xhclNTTDEcMBoGA1UEAxMTUG9sYXJzc2wgVGVzdCBFQyBDQRcNMTMwOTI0MTYz
+MTA4WhcNMjMwOTIyMTYzMTA4WjAUMBICAQoXDTEzMDkyNDE2MjgzOFqgcjBwMG4G
+A1UdIwRnMGWAFJ1tICRJAT8ry3i1Gbx+JMnb+zZ8oUKkQDA+MQswCQYDVQQGEwJO
+TDERMA8GA1UEChMIUG9sYXJTU0wxHDAaBgNVBAMTE1BvbGFyc3NsIFRlc3QgRUMg
+Q0GCCQDBQ+J+YkPM6DAJBgcqhkjOPQQBA2kAMGYCMQDVG95rrSSl4dJgbJ5vR1GW
+svEuEsAh35EhF1WrcadMuCeMQVX9cUPupFfQUpHyMfoCMQCKf0yv8pN9BAoi3FVm
+56meWPhUekgLKKMAobt2oJJY6feuiFU2YFGs1aF0rV6Bj+U=
+-----END X509 CRL-----
+-----BEGIN X509 CRL-----
+MIIBcTCB9wIBATAKBggqhkjOPQQDBDA+MQswCQYDVQQGEwJOTDERMA8GA1UEChMI
+UG9sYXJTU0wxHDAaBgNVBAMTE1BvbGFyc3NsIFRlc3QgRUMgQ0EXDTEzMDkyNDE2
+MzEwOFoXDTIzMDkyMjE2MzEwOFowFDASAgEKFw0xMzA5MjQxNjI4MzhaoHIwcDBu
+BgNVHSMEZzBlgBSdbSAkSQE/K8t4tRm8fiTJ2/s2fKFCpEAwPjELMAkGA1UEBhMC
+TkwxETAPBgNVBAoTCFBvbGFyU1NMMRwwGgYDVQQDExNQb2xhcnNzbCBUZXN0IEVD
+IENBggkAwUPifmJDzOgwCgYIKoZIzj0EAwQDaQAwZgIxAL/VFrDIYUECsS0rVpAy
+6zt/CqeAZ1sa/l5LTaG1XW286n2Kibipr6EpkYZNYIQILgIxAI0wb3Py1DHPWpYf
+/BFBH7C3KYq+nWTrLeEnhrjU1LzG/CiQ8lnuskya6lw/P3lJ/A==
+-----END X509 CRL-----      

tests/suites/test_suite_x509parse.data

@@ -198,6 +198,10 @@ X509 CRL Information EC, SHA512 Digest
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_SHA512_C
 mbedtls_x509_crl_info:"data_files/crl-ec-sha512.pem":"CRL version   \: 2\nissuer name   \: C=NL, O=PolarSSL, CN=Polarssl Test EC CA\nthis update   \: 2013-09-24 16\:31\:08\nnext update   \: 2023-09-22 16\:31\:08\nRevoked certificates\:\nserial number\: 0A revocation date\: 2013-09-24 16\:28\:38\nsigned using  \: ECDSA with SHA512\n"
 
+X509 CRL Malformed Input (trailing spaces at end of file)
+depends_on:MBEDTLS_PEM_PARSE_C
+mbedtls_x509_crl_parse:"data_files/crl-malformed-trailing-spaces.pem":MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT
+
 X509 CSR Information RSA with MD4
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_MD4_C
 mbedtls_x509_csr_info:"data_files/server1.req.md4":"CSR version   \: 1\nsubject name  \: C=NL, O=PolarSSL, CN=PolarSSL Server 1\nsigned using  \: RSA with MD4\nRSA key size  \: 2048 bits\n"

tests/suites/test_suite_x509parse.function

@@ -163,6 +163,22 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_FS_IO:MBEDTLS_X509_CRL_PARSE_C */
+void mbedtls_x509_crl_parse( char *crl_file, int result )
+{
+    mbedtls_x509_crl   crl;
+    char buf[2000];
+
+    mbedtls_x509_crl_init( &crl );
+    memset( buf, 0, 2000 );
+
+    TEST_ASSERT( mbedtls_x509_crl_parse_file( &crl, crl_file ) == result );
+
+exit:
+    mbedtls_x509_crl_free( &crl );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_FS_IO:MBEDTLS_X509_CSR_PARSE_C */
 void mbedtls_x509_csr_info( char *csr_file, char *result_str )
 {