add record parser

1 files changed, 193 insertions, 0 deletions

diff --git a/src/record.c b/src/record.c
new file mode 100644
index 0000000..7ba40a3
--- /dev/null
+++ b/src/record.c
@@ -0,0 +1,193 @@
+/*
+ * src/record.c
+ * (c) 2021 Jonas Gunz <himself@jonasgunz.de>
+ * License: MIT
+ */
+
+/* https://datatracker.ietf.org/doc/html/rfc1035#section-3.3 */
+
+#include "record.h"
+
+/*
+ * Prototypes for rdata from string functions
+ * Arguments:
+ *	_str:	String representing rdata
+ *	_rdata:	A buffer containing the raw rdata will be alloced here
+ * Return: Length of alloced _rdata buffer, <0 on error
+ */
+
+/* Obsolete record types. Will throw error. */
+static ssize_t record_rdata_obsolete(char* _str, void** _rdata);
+
+/* Unimplemented record types. Will throw error. */
+static ssize_t record_rdata_not_implemented(char* _str, void** _rdata);
+
+/* rdata that does not need conversion from string form */
+static ssize_t record_rdata_verbatim(char* _str, void** _rdata);
+
+/* IPv4 Addresses */
+static ssize_t record_rdata_a(char* _str, void** _rdata);
+
+/* Start of authority */
+static ssize_t record_rdata_soa(char* _str, void** _rdata);
+
+static const char* const record_types[] = {
+	"A",
+	"NS",
+	"MD",
+	"MF",
+	"CNAME",
+	"SOA",
+	"MB",
+	"MG",
+	"MR",
+	"NULL",
+	"WKS",
+	"PTR",
+	"HINFO",
+	"MINFO",
+	"MX",
+	"TXT"
+};
+static const uint16_t record_types_len = sizeof(record_types) / sizeof(char*);
+
+static ssize_t (*record_rdata_creator[])(char*, void**) = {
+	&record_rdata_a, /* A */
+	&record_rdata_verbatim, /* NS */
+	&record_rdata_obsolete, /* MD */
+	&record_rdata_obsolete, /* MF */
+	&record_rdata_verbatim, /* CNAME */
+	&record_rdata_soa, /* SOA */
+
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+	&record_rdata_not_implemented,
+};
+
+static const char* const record_classes[] = {
+	"IN",
+	"CS",
+	"CH",
+	"HS"
+};
+static const uint16_t record_classes_len = sizeof(record_classes) / sizeof(char*);
+
+/* Implementation of RDATA cobverters */
+
+static ssize_t record_rdata_obsolete(char* _str, void** _rdata) {
+	LOGPRINTF(_LOG_ERROR, "Record type not obsolete");
+	return -1;
+}
+
+static ssize_t record_rdata_not_implemented(char* _str, void** _rdata) {
+	LOGPRINTF(_LOG_ERROR, "Record type not implemented");
+	return -1;
+}
+
+static ssize_t record_rdata_verbatim(char* _str, void** _rdata) {
+	size_t len;
+
+	if ( !_str || !_rdata )
+		return -1;
+
+	len = strlen(_str) + 1; /* Including \0 */
+
+	*_rdata = malloc(len);
+
+	if ( !*_rdata )
+		return -1;
+
+	strncpy(*_rdata, _str, len);
+
+	return (signed) len;
+}
+
+static ssize_t record_rdata_a(char* _str, void** _rdata) {
+	char* tok;
+	char* str;
+	char* end;
+	size_t len;
+	int i;
+
+	if ( !_str || !_rdata )
+		return -1;
+
+	len = strlen(_str) + 1;
+	str = malloc(len);
+	strncpy(str, _str, len);
+
+	*_rdata = malloc(4);
+	if ( !*_rdata )
+		return -1;
+
+	tok = strtok(str, ".");
+	if( !tok )
+		goto err;
+
+	((uint8_t*)(*_rdata))[3] = (uint8_t) strtol(tok, &end, 10);
+
+	if( *end != '\0' )
+		goto err;
+
+	for( i=2; i>=0; i-- ) {
+		tok = strtok(NULL, ".");
+
+		if( !tok )
+			goto err;
+
+		((uint8_t*)(*_rdata))[i] = (uint8_t) strtol(tok, &end, 10);
+
+		if( *end != '\0' )
+			goto err;
+	}
+
+	free(str);
+	return 4;
+err:
+	free(str);
+	return -1;
+}
+
+static ssize_t record_rdata_soa(char* _str, void** _rdata) {
+	LOGPRINTF(_LOG_ERROR, "Record type not implemented");
+	return -1;
+}
+
+
+/* Other methods */
+
+static uint16_t record_match_from_array(char* _str, const char* const _arr[], uint16_t _len) {
+	uint16_t i;
+
+	for( i=0; i<_len; i++ ){
+		if ( strcasecmp( _str, _arr[i] ) == 0 )
+			return i+1; /* Indices start with 1 */
+	}
+
+	return 0;
+}
+
+uint16_t record_class_from_str(char* _str) {
+	return record_match_from_array(_str, record_classes, record_classes_len);
+}
+
+uint16_t record_type_from_str(char* _str) {
+	return record_match_from_array(_str, record_types, record_types_len);
+}
+
+ssize_t record_rdata_from_str(void** _rdata, char *_str, uint16_t _rdtype) {
+	if ( _rdtype >= record_types_len )
+		return -1;
+
+	if ( !_rdata || !_str )
+		return -1;
+
+	return (*record_rdata_creator)(_str, _rdata);
+}