ASN.1: Introduce helper function to free ASN.1 sequence

Author: Hanno Becker

include/mbedtls/asn1.h

@@ -275,6 +275,16 @@ int mbedtls_asn1_get_bitstring( unsigned char **p, const unsigned char *end,
 int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
                              size_t *len );
 
+/**
+ * \brief          Free a heap-allocated linked list presentation of
+ *                 an ASN.1 sequence, including the first element.
+ *
+ * \param seq      The address of the first sequence component. This may
+ *                 be \c NULL, in which case this functions returns
+ *                 immediately.
+ */
+void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq );
+
 /**
  * \brief       This function parses and splits an ASN.1 "SEQUENCE OF <tag>"
  *              and updates the source buffer pointer to immediately behind

library/asn1parse.c

@@ -229,7 +229,16 @@ int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end
     return( 0 );
 }
 
-
+void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq )
+{
+    while( seq != NULL )
+    {
+        mbedtls_asn1_sequence *next = seq->next;
+        mbedtls_platform_zeroize( seq, sizeof( *seq ) );
+        mbedtls_free( seq );
+        seq = next;
+    }
+}
 
 /*
  *  Parses and splits an ASN.1 "SEQUENCE OF <tag>"