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Finish OCSP response verification

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Complete the code that implements the checks between the relationship
between the requested certificate and the OCSP response issuer as part
of the verification process. The checks essentially use the information
in the OCSP response and the supplied certificate chains to:

    * Check whether the issuer is the parent of the requested cert

failing that, we check that

    * There is a parent for the issuer in one of the supplied cert
      chains
    * The issuer's parent is also the parent of the requested cert

If either of the two checks succeeds, we accept this verification step.
This commit is contained in:
Andres Amaya Garcia
2017-11-15 11:05:19 +00:00
parent 6aa52ffc56
commit 94fe8c196e
1 changed files with 69 additions and 21 deletions
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90
library/x509_ocsp.c
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@@ -1423,16 +1423,22 @@ exit:
static int x509_ocsp_is_parent_crt(
mbedtls_x509_ocsp_single_response *single_resp,
mbedtls_x509_crt *crt,
mbedtls_x509_crt *child,
mbedtls_x509_crt *parent,
int is_trust_ca,
int *is_parent )
{
int ret;
*is_parent = 0;
/*
* Check parental relationship using information in the OCSP response
*/
/* Check hash of parent's DN */
ret = x509_ocsp_mdcmp( single_resp->md_alg, crt->subject_raw.p,
crt->subject_raw.len,
ret = x509_ocsp_mdcmp( single_resp->md_alg, parent->subject_raw.p,
parent->subject_raw.len,
single_resp->issuer_name_hash.p );
if( ret < 0 )
return( ret );
@@ -1440,13 +1446,41 @@ static int x509_ocsp_is_parent_crt(
return( 0 );
/* Check hash of parent's public key */
ret = x509_ocsp_mdcmp( single_resp->md_alg, crt->pk_raw.p, crt->pk_raw.len,
ret = x509_ocsp_mdcmp( single_resp->md_alg, parent->pk_raw.p,
parent->pk_raw.len,
single_resp->issuer_key_hash.p );
if( ret < 0 )
return( ret );
else if( ret != 0 )
return( 0 );
/*
* Confirm parental relationship using the child certificate
*/
/* Basic parenting skills (name, CA bit, key usage) */
if( x509_ocsp_crt_check_parent( child, parent, is_trust_ca ) != 0 )
{
return( 0 );
}
/* Signature */
if( x509_ocsp_crt_check_signature( child, parent ) != 0 )
{
return( 0 );
}
/*
* Optional time check.
*
* TODO: Not sure whether we should accept time-invalid certificates
*/
if( mbedtls_x509_time_is_past( &parent->valid_to ) ||
mbedtls_x509_time_is_future( &parent->valid_from ) )
{
return( 0 );
}
/* Found parent of the requested certificate's status */
*is_parent = 1;
@@ -1455,7 +1489,9 @@ static int x509_ocsp_is_parent_crt(
static int x509_ocsp_find_parent_crt(
mbedtls_x509_ocsp_single_response *single_resp,
mbedtls_x509_crt *child,
mbedtls_x509_crt *chain,
int is_trust_ca,
mbedtls_x509_crt **parent )
{
int ret;
@@ -1466,8 +1502,8 @@ static int x509_ocsp_find_parent_crt(
for( cur = chain; cur != NULL; cur = cur->next )
{
if( ( ret = x509_ocsp_is_parent_crt( single_resp, cur,
&is_parent ) ) != 0 )
if( ( ret = x509_ocsp_is_parent_crt( single_resp, child, cur,
is_trust_ca, &is_parent ) ) != 0 )
{
return( ret );
}
@@ -1493,7 +1529,7 @@ static int x509_ocsp_find_parent_crt(
*/
static int x509_ocsp_verify_response_issuer(
mbedtls_x509_ocsp_single_response *single_resp,
mbedtls_x509_crt *crt,
mbedtls_x509_crt *req_crt,
mbedtls_x509_crt *chain,
mbedtls_x509_crt *trust_ca,
mbedtls_x509_crt *issuer,
@@ -1501,10 +1537,11 @@ static int x509_ocsp_verify_response_issuer(
{
int ret;
int is_parent = 0;
mbedtls_x509_crt *parent;
int is_trust_ca = 0;
mbedtls_x509_crt *parent = NULL;
/* Check whether the issuer is the parent of the requested certificate */
if( ( ret = x509_ocsp_is_parent_crt( single_resp, issuer,
if( ( ret = x509_ocsp_is_parent_crt( single_resp, req_crt, issuer, 0,
&is_parent ) ) != 0 )
{
return( ret );
@@ -1512,10 +1549,10 @@ static int x509_ocsp_verify_response_issuer(
else if( is_parent != 0 )
{
/*
* Condition 2 has been met, try to build a chain of trust from the
* crt upwards
* Condition 2 was satisfied: The issuer is the parent of the requested
* certificate
*/
// TODO
return( 0 );
}
#if defined(MBEDTLS_X509_CHECK_EXTENDED_KEY_USAGE)
@@ -1529,7 +1566,7 @@ static int x509_ocsp_verify_response_issuer(
}
/*
* Try to find the parent of the requested certificate.
* Check that issuer and requested certificate have the same parent.
*
* TODO: Currently we try to locate the parent in the untrusted chain,
* and the trust_ca chain. Should we also look in the OCSP response's
@@ -1539,15 +1576,15 @@ static int x509_ocsp_verify_response_issuer(
* speaking we do notuse the parent to directly verify the response's,
* so we do not search the parent
*/
if( ( ret = x509_ocsp_find_parent_crt( single_resp, chain,
if( ( ret = x509_ocsp_find_parent_crt( single_resp, issuer, trust_ca, 1,
&parent ) ) != 0 )
{
return( ret );
}
else if( parent == NULL )
{
if( ( ret = x509_ocsp_find_parent_crt( single_resp, trust_ca,
&parent ) ) != 0 )
if( ( ret = x509_ocsp_find_parent_crt( single_resp, issuer, chain,
0, &parent ) ) != 0 )
{
return( ret );
}
@@ -1557,14 +1594,25 @@ static int x509_ocsp_verify_response_issuer(
return( 0 );
}
}
else
is_trust_ca = 1;
/*
* Condition 3 has been met, try to build a chain of trust from the
* issuer upwards and verify that *parent is the parent of crt
*/
// TODO
if( ( ret = x509_ocsp_is_parent_crt( single_resp, req_crt, parent,
is_trust_ca, &is_parent ) ) != 0 )
{
return( ret );
}
else if( is_parent != 0 )
{
/*
* Condition 3 was satisfied: The issuer and requested certificate
* have the same parent
*/
return( 0 );
}
#endif /* MBEDTLS_X509_CHECK_EXTENDED_KEY_USAGE */
*flags |= MBEDTLS_X509_BADOCSP_RESPONSE_ISSUER_NOT_TRUSTED;
return( 0 );
}