Fix implementation of VERIFY_OPTIONAL verification mode
This commit changes the behaviour of mbedtls_ssl_parse_certificate
to make the two authentication modes SSL_VERIFY_REQUIRED and
SSL_VERIFY_OPTIONAL be in the following relationship:
Mode == SSL_VERIFY_REQUIRED
<=> Mode == SSL_VERIFY_OPTIONAL + check verify result
Also, it changes the behaviour to perform the certificate chain
verification even if the trusted CA chain is empty. Previously, the
function failed in this case, even when using optional verification,
which was brought up in #864.
diff --git a/ChangeLog b/ChangeLog
index a64de5d..d33897c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,12 @@
* Wipe stack buffers in RSA private key operations
(rsa_rsaes_pkcs1_v15_decrypt(), rsa_rsaes_oaep_decrypt).
Found by Laurent Simon.
+ * Accept empty trusted CA chain in authentication mode
+ SSL_VERIFY_OPTIONAL. Fixes #864. Found by jethrogb.
+ * Fix implementation of ssl_parse_certificate
+ to not annihilate fatal errors in authentication mode
+ SSL_VERIFY_OPTIONAL and to reflect bad EC curves
+ within verification result.
= mbed TLS 1.3.19 branch released 2017-03-08
diff --git a/include/polarssl/x509.h b/include/polarssl/x509.h
index cd01539..adaacff 100644
--- a/include/polarssl/x509.h
+++ b/include/polarssl/x509.h
@@ -97,6 +97,8 @@
#define BADCERT_KEY_USAGE 0x0800 /**< Usage does not match the keyUsage extension. */
#define BADCERT_EXT_KEY_USAGE 0x1000 /**< Usage does not match the extendedKeyUsage extension. */
#define BADCERT_NS_CERT_TYPE 0x2000 /**< Usage does not match the nsCertType extension. */
+#define BADCERT_BAD_KEY 0x10000 /**< Bad key (e.g. unsupported elliptic curve in use) */
+
/* \} name */
/* \} addtogroup x509_module */
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 7cf968d..5779229 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2841,12 +2841,6 @@
if( ssl->authmode != SSL_VERIFY_NONE )
{
- if( ssl->ca_chain == NULL )
- {
- SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
- return( POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED );
- }
-
/*
* Main check: verify certificate
*/
@@ -2872,6 +2866,8 @@
if( pk_can_do( pk, POLARSSL_PK_ECKEY ) &&
! ssl_curve_is_acceptable( ssl, pk_ec( *pk )->grp.id ) )
{
+ ssl->session_negotiate->verify_result |= BADCERT_BAD_KEY;
+
SSL_DEBUG_MSG( 1, ( "bad certificate (EC key curve)" ) );
if( ret == 0 )
ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
@@ -2889,8 +2885,36 @@
ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
}
- if( ssl->authmode != SSL_VERIFY_REQUIRED )
+ /* x509_crt_verify_with_profile is supposed to report a
+ * verification failure through POLARSSL_ERR_X509_CERT_VERIFY_FAILED,
+ * with details encoded in the verification flags. All other kinds
+ * of error codes, including those from the user provided f_vrfy
+ * functions, are treated as fatal and lead to a failure of
+ * ssl_parse_certificate even if verification was optional. */
+ if( ssl->authmode == SSL_VERIFY_OPTIONAL &&
+ ( ret == POLARSSL_ERR_X509_CERT_VERIFY_FAILED ||
+ ret == POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE ) )
+ {
ret = 0;
+ }
+
+ if( ssl->ca_chain == NULL && ssl->authmode == SSL_VERIFY_REQUIRED )
+ {
+ SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
+ ret = POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED;
+ }
+
+#if defined(POLARSSL_DEBUG_C)
+ if( ssl->session_negotiate->verify_result != 0 )
+ {
+ SSL_DEBUG_MSG( 3, ( "! Certificate verification flags %x",
+ ssl->session_negotiate->verify_result ) );
+ }
+ else
+ {
+ SSL_DEBUG_MSG( 3, ( "Certificate verification flags clear" ) );
+ }
+#endif /* POLARSSL_DEBUG_C */
}
SSL_DEBUG_MSG( 2, ( "<= parse certificate" ) );
diff --git a/library/x509_crt.c b/library/x509_crt.c
index a3517f6..16a29b5 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1403,6 +1403,7 @@
{ BADCERT_KEY_USAGE, "Usage does not match the keyUsage extension" },
{ BADCERT_EXT_KEY_USAGE, "Usage does not match the extendedKeyUsage extension" },
{ BADCERT_NS_CERT_TYPE, "Usage does not match the nsCertType extension" },
+ { BADCERT_BAD_KEY, "The certificate uses an invalid key (e.g. unsupported elliptic curve)" },
{ 0, NULL }
};