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Fix implementation of VERIFY_OPTIONAL verification mode

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This commit changes the behaviour of mbedtls_ssl_parse_certificate
to make the two authentication modes MBEDTLS_SSL_VERIFY_REQUIRED and
MBEDTLS_SSL_VERIFY_OPTIONAL be in the following relationship:

    Mode == MBEDTLS_SSL_VERIFY_REQUIRED
<=> Mode == MBEDTLS_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.
This commit is contained in:
Hanno Becker 2017-05-08 16:31:14 +01:00
parent ddc6e52cc1
commit 39ae8cd207
2 changed files with 29 additions and 11 deletions
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7
ChangeLog
View file

@ -17,6 +17,13 @@ Bugfix
that triggered the alert. that triggered the alert.
* In SSLv3, if refusing a renegotiation attempt, don't process any further * In SSLv3, if refusing a renegotiation attempt, don't process any further
data. data.
* Accept empty trusted CA chain in authentication mode
MBEDTLS_SSL_VERIFY_OPTIONAL.
Fixes #864. Found by jethrogb.
* Fix implementation of mbedtls_ssl_parse_certificate
to not annihilate fatal errors in authentication mode
MBEDTLS_SSL_VERIFY_OPTIONAL and to reflect bad EC curves
within verification result.
Changes Changes
* Send fatal alerts in many more cases instead of dropping the connection. * Send fatal alerts in many more cases instead of dropping the connection.

29
library/ssl_tls.c
View file

@ -4472,14 +4472,6 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
ca_crl = ssl->conf->ca_crl; ca_crl = ssl->conf->ca_crl;
} }
if( ca_chain == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_BAD_CERT );
return( MBEDTLS_ERR_SSL_CA_CHAIN_REQUIRED );
}
/* /*
* Main check: verify certificate * Main check: verify certificate
*/ */
@ -4508,6 +4500,8 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
if( mbedtls_pk_can_do( pk, MBEDTLS_PK_ECKEY ) && if( mbedtls_pk_can_do( pk, MBEDTLS_PK_ECKEY ) &&
mbedtls_ssl_check_curve( ssl, mbedtls_pk_ec( *pk )->grp.id ) != 0 ) mbedtls_ssl_check_curve( ssl, mbedtls_pk_ec( *pk )->grp.id ) != 0 )
{ {
ssl->session_negotiate->verify_result |= MBEDTLS_X509_BADCERT_BAD_KEY;
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate (EC key curve)" ) ); MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate (EC key curve)" ) );
if( ret == 0 ) if( ret == 0 )
ret = MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE; ret = MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE;
@ -4525,8 +4519,24 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
ret = MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE; ret = MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE;
} }
if( authmode == MBEDTLS_SSL_VERIFY_OPTIONAL ) /* mbedtls_x509_crt_verify_with_profile is supposed to report a
* verification failure through MBEDTLS_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( authmode == MBEDTLS_SSL_VERIFY_OPTIONAL &&
( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED ||
ret == MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE ) )
{
ret = 0; ret = 0;
}
if( ca_chain == NULL && authmode == MBEDTLS_SSL_VERIFY_REQUIRED )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
ret = MBEDTLS_ERR_SSL_CA_CHAIN_REQUIRED;
}
if( ret != 0 ) if( ret != 0 )
{ {
@ -4558,6 +4568,7 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
alert ); alert );
} }
} }
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate" ) ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate" ) );