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Simplify implementation of mbedtls_x509_get_name()

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X.509 names in ASN.1 are encoded as ASN.1 SEQUENCEs of ASN.1 SETs
of Attribute-Value pairs, one for each component in the name. (For
example, there could be an Attribute-Value pair for "DN=www.mbedtls.org").

So far, `mbedtls_x509_get_name()` parsed such names by two nested
loops, the outer one traversing the outer ASN.1 SEQUENCE and the
inner one the ASN.1 SETs.

This commit introduces a helper function `x509_set_sequence_iterate()`
which implements an iterator through an ASN.1 name buffer; the state
of the iterator is a triple consisting of
- the current read pointer
- the end of the current SET
- the end of the name buffer
The iteration step reads a new SET if the current read pointer has
reached the end of the current SET, and afterwards reads the next
AttributeValue pair.
This way, iteration through the X.509 name data can be implemented
in a single loop, which increases readability and slightly reduces
the code-size.
This commit is contained in:
Hanno Becker 2019-02-20 09:45:17 +00:00
parent b40dc58a83
commit 3470d592ce
1 changed files with 43 additions and 41 deletions
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84
library/x509.c
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@ -350,30 +350,31 @@ int mbedtls_x509_get_rsassa_pss_params( const mbedtls_x509_buf *params,
*/
static int x509_get_attr_type_value( unsigned char **p,
const unsigned char *end,
mbedtls_x509_name *cur )
mbedtls_x509_buf *oid,
mbedtls_x509_buf *val )
{
int ret;
size_t len;
mbedtls_x509_buf *oid;
mbedtls_x509_buf *val;
if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
end = *p + len;
oid = &cur->oid;
if( ( ret = mbedtls_asn1_get_tag( p, end, &oid->len, MBEDTLS_ASN1_OID ) ) != 0 )
ret = mbedtls_asn1_get_tag( p, end, &oid->len, MBEDTLS_ASN1_OID );
if( ret != 0 )
return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
oid->tag = MBEDTLS_ASN1_OID;
oid->p = *p;
*p += oid->len;
if( ( end - *p ) < 1 )
if( *p == end )
{
return( MBEDTLS_ERR_X509_INVALID_NAME +
MBEDTLS_ERR_ASN1_OUT_OF_DATA );
}
if( !MBEDTLS_ASN1_IS_STRING_TAG( **p ) )
{
@ -381,7 +382,6 @@ static int x509_get_attr_type_value( unsigned char **p,
MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
}
val = &cur->val;
val->tag = *(*p)++;
if( ( ret = mbedtls_asn1_get_len( p, end, &val->len ) ) != 0 )
@ -395,9 +395,6 @@ static int x509_get_attr_type_value( unsigned char **p,
return( MBEDTLS_ERR_X509_INVALID_NAME +
MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
}
cur->next = NULL;
return( 0 );
}
@ -424,57 +421,62 @@ static int x509_get_attr_type_value( unsigned char **p,
* same set so that they are "merged" together in the functions that consume
* this list, eg mbedtls_x509_dn_gets().
*/
int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
mbedtls_x509_name *cur )
static int x509_set_sequence_iterate( unsigned char **p,
unsigned char const **end_set,
unsigned char const *end,
mbedtls_x509_buf *oid,
mbedtls_x509_buf *val )
{
int ret;
size_t set_len;
const unsigned char *end_set;
/* don't use recursion, we'd risk stack overflow if not optimized */
while( 1 )
if( *p == *end_set )
{
/*
* parse SET
*/
if( ( ret = mbedtls_asn1_get_tag( p, end, &set_len,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET ) ) != 0 )
/* Parse next TLV of ASN.1 SET structure. */
ret = mbedtls_asn1_get_tag( p, end, &set_len,
MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SET );
if( ret != 0 )
return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
end_set = *p + set_len;
*end_set = *p + set_len;
}
while( 1 )
{
if( ( ret = x509_get_attr_type_value( p, end_set, cur ) ) != 0 )
return( ret );
return( x509_get_attr_type_value( p, *end_set, oid, val ) );
}
if( *p == end_set )
break;
int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
mbedtls_x509_name *cur )
{
int ret;
const unsigned char *end_set;
/* Mark this item as being no the only one in a set */
end_set = *p;
while( 1 )
{
ret = x509_set_sequence_iterate( p, &end_set, end,
&cur->oid, &cur->val );
if( ret != 0 )
return( ret );
if( *p != end_set )
cur->next_merged = 1;
cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
if( cur->next == NULL )
return( MBEDTLS_ERR_X509_ALLOC_FAILED );
cur = cur->next;
if( *p == end )
{
cur->next = NULL;
break;
}
/*
* continue until end of SEQUENCE is reached
*/
if( *p == end )
return( 0 );
cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
if( cur->next == NULL )
return( MBEDTLS_ERR_X509_ALLOC_FAILED );
cur = cur->next;
}
return( 0 );
}
static int x509_parse_int( unsigned char **p, size_t n, int *res )