Make use of cb to build linked list presentation of SubjectAltName
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 5d43a44..3dfa863 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -599,80 +599,13 @@
     return( 0 );
 }
 
-static int x509_get_subject_alt_name( unsigned char **p,
+static int x509_get_subject_alt_name( unsigned char *p,
                                       const unsigned char *end,
                                       mbedtls_x509_sequence *subject_alt_name )
 {
-    int ret;
-    size_t len, tag_len;
-    mbedtls_asn1_buf *buf;
-    unsigned char tag;
-    mbedtls_asn1_sequence *cur = subject_alt_name;
-
-    /* Get main sequence tag */
-    if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
-            MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
-
-    if( *p + len != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
-
-    while( *p < end )
-    {
-        if( ( end - *p ) < 1 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_OUT_OF_DATA );
-
-        tag = **p;
-        (*p)++;
-        if( ( ret = mbedtls_asn1_get_len( p, end, &tag_len ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
-
-        if( ( tag & MBEDTLS_ASN1_TAG_CLASS_MASK ) !=
-                MBEDTLS_ASN1_CONTEXT_SPECIFIC )
-        {
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
-        }
-
-        /* Skip everything but DNS name */
-        if( tag != ( MBEDTLS_ASN1_CONTEXT_SPECIFIC | 2 ) )
-        {
-            *p += tag_len;
-            continue;
-        }
-
-        /* Allocate and assign next pointer */
-        if( cur->buf.p != NULL )
-        {
-            if( cur->next != NULL )
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS );
-
-            cur->next = mbedtls_calloc( 1, sizeof( mbedtls_asn1_sequence ) );
-
-            if( cur->next == NULL )
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                        MBEDTLS_ERR_ASN1_ALLOC_FAILED );
-
-            cur = cur->next;
-        }
-
-        buf = &(cur->buf);
-        buf->tag = tag;
-        buf->p = *p;
-        buf->len = tag_len;
-        *p += buf->len;
-    }
-
-    /* Set final sequence entry's next pointer to NULL */
-    cur->next = NULL;
-
-    if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
-
-    return( 0 );
+    return( x509_subject_alt_name_traverse( p, end,
+                                            x509_get_subject_alt_name_cb,
+                                            (void*) &subject_alt_name ) );
 }
 
 /*
@@ -793,9 +726,12 @@
             /* Parse subject alt name */
             crt->subject_alt_raw.p = *p;
             crt->subject_alt_raw.len = end_ext_octet - *p;
-            if( ( ret = x509_get_subject_alt_name( p, end_ext_octet,
+            if( ( ret = x509_get_subject_alt_name( *p, end_ext_octet,
                     &crt->subject_alt_names ) ) != 0 )
+            {
                 return( ret );
+            }
+            *p = end_ext_octet;
             break;
 
         case MBEDTLS_X509_EXT_NS_CERT_TYPE: