mbedtls_asn1_store_named_data: clarify val allocation behavior
Document how mbedtls_asn1_store_named_data allocates val.p in the new
or modified entry.
Change the behavior to be more regular, always setting the new length
to val_len. This does not affect the previous documented behavior
since this aspect was not documented. This does not affect current
usage in Mbed TLS's X.509 module where calls with the same OID always
use the same size for the associated value.
diff --git a/include/mbedtls/asn1write.h b/include/mbedtls/asn1write.h
index 8ecab4e..9824146 100644
--- a/include/mbedtls/asn1write.h
+++ b/include/mbedtls/asn1write.h
@@ -334,9 +334,13 @@
* through (will be updated in case of a new entry).
* \param oid The OID to look for.
* \param oid_len The size of the OID.
- * \param val The data to store (can be \c NULL if you want to fill
- * it by hand).
+ * \param val The associated data to store. If this is \c NULL,
+ * no data is copied to the new or existing buffer.
* \param val_len The minimum length of the data buffer needed.
+ * If this is 0, do not allocate a buffer for the associated
+ * data.
+ * If the OID was already present, enlarge, shrink or free
+ * the existing buffer to fit \p val_len.
*
* \return A pointer to the new / existing entry on success.
* \return \c NULL if if there was a memory allocation error.
diff --git a/library/asn1write.c b/library/asn1write.c
index 98c6766..a138d0b 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -432,18 +432,26 @@
memcpy( cur->oid.p, oid, oid_len );
cur->val.len = val_len;
- cur->val.p = mbedtls_calloc( 1, val_len );
- if( cur->val.p == NULL )
+ if( val_len != 0 )
{
- mbedtls_free( cur->oid.p );
- mbedtls_free( cur );
- return( NULL );
+ cur->val.p = mbedtls_calloc( 1, val_len );
+ if( cur->val.p == NULL )
+ {
+ mbedtls_free( cur->oid.p );
+ mbedtls_free( cur );
+ return( NULL );
+ }
}
cur->next = *head;
*head = cur;
}
- else if( cur->val.len < val_len )
+ else if( val_len == 0 )
+ {
+ mbedtls_free( cur->val.p );
+ cur->val.p = NULL;
+ }
+ else if( cur->val.len != val_len )
{
/*
* Enlarge existing value buffer if needed