From 3583eb1a470ae6d1ccd2f12e5664594414e33a29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20De=20Keersmaeker?=
<francois.dekeersmaeker@uclouvain.be>
Date: Wed, 10 Jul 2024 11:09:38 +0200
Subject: [PATCH] Updated DNS lib
---
include/dns.h | 42 ++++++++++++--
src/dns.c | 149 ++++++++++++++++++++++++++++++++++++++++++++------
2 files changed, 170 insertions(+), 21 deletions(-)
diff --git a/include/dns.h b/include/dns.h
index 7b6975e..0384b90 100644
--- a/include/dns.h
+++ b/include/dns.h
@@ -1,5 +1,6 @@
/**
- * @file include/dns.h
+ * @file include/parsers/dns.h
+ * @author François De Keersmaeker (francois.dekeersmaeker@uclouvain.be)
* @brief DNS message parser
* @date 2022-09-09
*
@@ -15,6 +16,9 @@
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
#include <arpa/inet.h>
#include "packet_utils.h"
#include "dns_map.h"
@@ -71,7 +75,7 @@ typedef struct dns_header {
*/
typedef struct dns_question {
char *qname;
- dns_rr_type_t qtype;
+ uint16_t qtype;
uint16_t qclass;
} dns_question_t;
@@ -89,7 +93,7 @@ typedef union {
*/
typedef struct dns_resource_record {
char *name;
- dns_rr_type_t rtype;
+ uint16_t rtype;
uint16_t rclass;
uint32_t ttl;
uint16_t rdlength;
@@ -187,10 +191,10 @@ dns_question_t* dns_get_question(dns_question_t *questions, uint16_t qdcount, ch
/**
* @brief Retrieve the IP addresses corresponding to a given domain name in a DNS Answers list.
- *
+ *
* Searches a DNS Answer list for a specific domain name and returns the corresponding IP address.
* Processes each Answer recursively if the Answer Type is a CNAME.
- *
+ *
* @param answers DNS Answers list to search in
* @param ancount number of Answers in the list
* @param domain_name domain name to search for
@@ -199,6 +203,34 @@ dns_question_t* dns_get_question(dns_question_t *questions, uint16_t qdcount, ch
ip_list_t dns_get_ip_from_name(dns_resource_record_t *answers, uint16_t ancount, char *domain_name);
+///// COMMUNICATE /////
+
+/**
+ * @brief Convert domain name to message format.
+ *
+ * @param dst converted domain name
+ * @param src domain name to convert
+ */
+void dns_convert_qname(char *dst, char *src, uint16_t len);
+
+/**
+ * @brief Send a DNS query for the given domain name.
+ *
+ * @param qname domain name to query for
+ * @param sockfd socket file descriptor
+ * @param server_addr DNS server IPv4 address
+ */
+void dns_send_query(char *qname, int sockfd, struct sockaddr_in *server_addr);
+
+/**
+ * @brief Receive a DNS response
+ *
+ * @param sockfd socket file descriptor
+ * @param server_addr DNS server IPv4 address
+ */
+dns_message_t dns_receive_response(int sockfd, struct sockaddr_in *server_addr);
+
+
///// DESTROY /////
/**
diff --git a/src/dns.c b/src/dns.c
index 5c31265..cf69502 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -1,5 +1,6 @@
/**
- * @file src/dns.c
+ * @file src/parsers/dns.c
+ * @author François De Keersmaeker (francois.dekeersmaeker@uclouvain.be)
* @brief DNS message parser
* @date 2022-09-09
*
@@ -191,7 +192,7 @@ dns_resource_record_t* dns_parse_rrs(uint16_t count, uint8_t *data, uint16_t *of
// Parse domain name
(rrs + i)->name = dns_parse_domain_name(data, offset);
// Parse rtype, rclass and TTL
- dns_rr_type_t rtype = ntohs(*((uint16_t *) (data + *offset)));
+ uint16_t rtype = ntohs(*((uint16_t *) (data + *offset)));
(rrs + i)->rtype = rtype;
(rrs + i)->rclass = ntohs(*((uint16_t *) (data + *offset + 2))) & DNS_CLASS_MASK;
(rrs + i)->ttl = ntohl(*((uint32_t *) (data + *offset + 4)));
@@ -199,7 +200,7 @@ dns_resource_record_t* dns_parse_rrs(uint16_t count, uint8_t *data, uint16_t *of
uint16_t rdlength = ntohs(*((uint16_t *) (data + *offset + 8)));
(rrs + i)->rdlength = rdlength;
*offset += 10;
- (rrs + i)->rdata = dns_parse_rdata(rtype, rdlength, data, offset);
+ (rrs + i)->rdata = dns_parse_rdata((dns_rr_type_t) rtype, rdlength, data, offset);
}
return rrs;
}
@@ -326,39 +327,48 @@ dns_question_t* dns_get_question(dns_question_t *questions, uint16_t qdcount, ch
/**
* @brief Retrieve the IP addresses corresponding to a given domain name in a DNS Answers list.
- *
+ *
* Searches a DNS Answer list for a specific domain name and returns the corresponding IP address.
* Processes each Answer recursively if the Answer Type is a CNAME.
- *
+ *
* @param answers DNS Answers list to search in
* @param ancount number of Answers in the list
* @param domain_name domain name to search for
* @return struct ip_list representing the list of corresponding IP addresses
*/
-ip_list_t dns_get_ip_from_name(dns_resource_record_t *answers, uint16_t ancount, char *domain_name) {
+ip_list_t dns_get_ip_from_name(dns_resource_record_t *answers, uint16_t ancount, char *domain_name)
+{
ip_list_t ip_list;
ip_list.ip_count = 0;
ip_list.ip_addresses = NULL;
char *cname = domain_name;
- for (uint16_t i = 0; i < ancount; i++) {
- if (strcmp((answers + i)->name, cname) == 0) {
+ for (uint16_t i = 0; i < ancount; i++)
+ {
+ if (strcmp((answers + i)->name, cname) == 0)
+ {
dns_rr_type_t rtype = (answers + i)->rtype;
if (rtype == A || rtype == AAAA)
{
// Handle IP list length
- if (ip_list.ip_addresses == NULL) {
- ip_list.ip_addresses = (ip_addr_t *) malloc(sizeof(ip_addr_t));
- } else {
+ if (ip_list.ip_addresses == NULL)
+ {
+ ip_list.ip_addresses = (ip_addr_t *)malloc(sizeof(ip_addr_t));
+ }
+ else
+ {
void *realloc_ptr = realloc(ip_list.ip_addresses, (ip_list.ip_count + 1) * sizeof(ip_addr_t));
- if (realloc_ptr == NULL) {
+ if (realloc_ptr == NULL)
+ {
// Handle realloc error
free(ip_list.ip_addresses);
fprintf(stderr, "Error reallocating memory for IP list.\n");
ip_list.ip_count = 0;
ip_list.ip_addresses = NULL;
return ip_list;
- } else {
- ip_list.ip_addresses = (ip_addr_t*) realloc_ptr;
+ }
+ else
+ {
+ ip_list.ip_addresses = (ip_addr_t *)realloc_ptr;
}
}
// Handle IP version and value
@@ -375,6 +385,113 @@ ip_list_t dns_get_ip_from_name(dns_resource_record_t *answers, uint16_t ancount,
}
+///// COMMUNICATE /////
+
+/**
+ * @brief Convert domain name to message format.
+ *
+ * @param dst converted domain name
+ * @param src domain name to convert
+ */
+void dns_convert_qname(char *dst, char *src, uint16_t len) {
+ int lock = 0; // Points to the next index to fill in the output array
+
+ // Start by iterating over each character in the input domain name
+ for (int i = 0; i < len; i++)
+ {
+ int segment_len = 0; // Length of the current segment
+
+ // Count the length of the current segment until we hit a dot or the end of the string
+ while (*(src + i) != '.' && *(src + i) != '\0')
+ {
+ *(dst + lock + 1 + segment_len) = *(src + i);
+ segment_len++;
+ i++;
+ }
+
+ *(dst + lock) = segment_len; // Prefix the segment with its length
+ lock += segment_len + 1; // Move the index past the current segment
+ }
+
+ *(dst + lock) = '\0'; // Null terminate the DNS label format string
+}
+
+/**
+ * @brief Send a DNS query for the given domain name.
+ *
+ * @param qname domain name to query for
+ * @param sockfd socket file descriptor
+ * @param server_addr DNS server IPv4 address
+ */
+void dns_send_query(char *qname, int sockfd, struct sockaddr_in *server_addr) {
+ // Buffer that will contain the message
+ uint16_t qname_len = strlen(qname);
+ uint16_t qname_labels_len = qname_len + sizeof(uint8_t) * 2;
+ uint16_t dns_questions_size = qname_labels_len + sizeof(uint16_t) * 2;
+ uint16_t dns_message_size = DNS_HEADER_SIZE + dns_questions_size;
+ uint8_t *buffer = (uint8_t *) malloc(dns_message_size);
+
+ // Populate DNS Header fields
+ dns_header_t dns_header;
+ dns_header.id = htons((uint16_t) getpid());
+ dns_header.flags = htons((uint16_t) (0b0000000100000000));
+ dns_header.qr = 0; // Query: qr = 0
+ dns_header.qdcount = htons((uint16_t) 1); // Only 1 question
+ dns_header.ancount = 0;
+ dns_header.nscount = 0;
+ dns_header.arcount = 0;
+
+ // Populate DNS Question fields
+ dns_question_t dns_question;
+ dns_question.qname = (char *)malloc(qname_labels_len);
+ dns_convert_qname(dns_question.qname, qname, qname_len);
+ dns_question.qtype = htons((uint16_t) A);
+ dns_question.qclass = htons((uint16_t) 1);
+
+ // Copy all DNS fields
+ memcpy(buffer, &dns_header, sizeof(uint16_t) * 2);
+ memcpy(buffer + sizeof(uint16_t) * 2, &(dns_header.qdcount), sizeof(uint16_t) * 4);
+ memcpy(buffer + DNS_HEADER_SIZE, dns_question.qname, qname_labels_len);
+ memcpy(buffer + DNS_HEADER_SIZE + qname_labels_len, &(dns_question.qtype), sizeof(uint16_t) * 2);
+
+ // Send DNS message
+ if (sendto(sockfd, buffer, dns_message_size, 0, (struct sockaddr *)server_addr, sizeof(*server_addr)) < 0)
+ {
+ perror("Failed sending DNS query.");
+ }
+
+ // Free memory
+ free(dns_question.qname);
+ free(buffer);
+}
+
+/**
+ * @brief Receive a DNS response.
+ *
+ * @param sockfd socket file descriptor
+ * @param server_addr DNS server IPv4 address
+ * @return received DNS message
+ */
+dns_message_t dns_receive_response(int sockfd, struct sockaddr_in *server_addr)
+{
+ // Receiving buffer
+ int bufsize = 65536;
+ uint8_t *buffer = (uint8_t *)malloc(bufsize);
+
+ // Await response
+ int n = recvfrom(sockfd, (char *)buffer, bufsize, 0, NULL, NULL);
+ if (n < 0)
+ {
+ perror("Failed receiving DNS response.");
+ exit(-1);
+ }
+
+ // Parse received DNS message
+ dns_message_t dns_message = dns_parse_message(buffer);
+ free(buffer);
+ return dns_message;
+}
+
///// DESTROY /////
/**
@@ -410,7 +527,7 @@ static void dns_free_rrs(dns_resource_record_t *rrs, uint16_t count) {
dns_resource_record_t rr = *(rrs + i);
if (rr.rdlength > 0) {
free(rr.name);
- dns_free_rdata(rr.rdata, rr.rtype);
+ dns_free_rdata(rr.rdata, (dns_rr_type_t) rr.rtype);
}
}
free(rrs);
@@ -539,7 +656,7 @@ void dns_print_rr(char* section_name, dns_resource_record_t rr) {
printf(" Class: %hd\n", rr.rclass);
printf(" TTL [s]: %d\n", rr.ttl);
printf(" Data length: %hd\n", rr.rdlength);
- printf(" RDATA: %s\n", dns_rdata_to_str(rr.rtype, rr.rdlength, rr.rdata));
+ printf(" RDATA: %s\n", dns_rdata_to_str((dns_rr_type_t) rr.rtype, rr.rdlength, rr.rdata));
}
/**
--
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