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libstrophe-gh/src/resolver.c
Dmitry Podgorny a45af3a929 resolver: srv_rr_list can be uninitialised 
Resolver assumes that srv_rr_list is empty at the beginning. Make it so
explicitly and let user pass uninitialised list as argument.
2016-09-02 12:39:10 +03:00

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/* resolver.h
* strophe XMPP client library -- DNS resolver
*
* Copyright (C) 2015 Dmitry Podgorny <pasis.ua@gmail.com>
*
* This software is provided AS-IS with no warranty, either express
* or implied.
*
* This program is dual licensed under the MIT and GPLv3 licenses.
*/
/** @file
* DNS resolver.
*/
#ifndef _WIN32
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h> /* res_query */
#endif /* _WIN32 */
#include <string.h> /* strncpy */
#include "ostypes.h"
#include "snprintf.h"
#include "resolver.h"
#define MESSAGE_HEADER_LEN 12
#define MESSAGE_RESPONSE 1
#define MESSAGE_T_SRV 33
#define MESSAGE_C_IN 1
struct message_header {
uint16_t id;
uint8_t octet2;
uint8_t octet3;
uint16_t qdcount;
uint16_t ancount;
uint16_t nscount;
uint16_t arcount;
};
#ifdef _WIN32
static int resolver_win32_srv_lookup(xmpp_ctx_t *ctx, const char *fulldomain,
resolver_srv_rr_t **srv_rr_list);
static int resolver_win32_srv_query(const char *fulldomain,
unsigned char *buf, size_t len);
#endif /* _WIN32 */
/* the same as ntohs(), but receives pointer to the value */
static uint16_t xmpp_ntohs_ptr(const void *ptr)
{
const uint8_t *p = (const uint8_t *)ptr;
return (uint16_t)((p[0] << 8U) + p[1]);
}
static uint8_t message_header_qr(const struct message_header *header)
{
return (header->octet2 >> 7) & 1;
}
static uint8_t message_header_rcode(const struct message_header *header)
{
return header->octet3 & 0x0f;
}
static unsigned message_name_get(const unsigned char *buf, size_t buf_len,
unsigned buf_offset,
char *name, size_t name_max)
{
size_t name_len = 0;
unsigned i = buf_offset;
unsigned pointer;
unsigned char label_len;
while ((label_len = buf[i++]) != 0) {
/* label */
if ((label_len & 0xc0) == 0) {
if (name != NULL) {
if (name_len != 0)
name[name_len++] = '.';
strncpy(&name[name_len], (char *)&buf[i], label_len);
}
i += label_len;
name_len += label_len;
/* pointer */
} else if ((label_len & 0xc0) == 0xc0) {
pointer = (label_len & 0x3f) << 8 | buf[i++];
(void)message_name_get(buf, buf_len, pointer, &name[name_len],
name_max - name_len);
/* pointer is always the last */
break;
/* The 10 and 01 combinations are reserved for future use. */
} else {
return 0;
}
}
if (label_len == 0 && name != NULL)
name[name_len] = '\0';
return i - buf_offset;
}
static unsigned message_name_len(const unsigned char *buf, size_t buf_len,
unsigned buf_offset)
{
return message_name_get(buf, buf_len, buf_offset, NULL, SIZE_MAX);
}
static void resolver_srv_list_sort(resolver_srv_rr_t **srv_rr_list)
{
resolver_srv_rr_t * rr_head;
resolver_srv_rr_t * rr_current;
resolver_srv_rr_t * rr_next;
resolver_srv_rr_t * rr_prev;
int swap;
rr_head = *srv_rr_list;
if ((rr_head == NULL) || (rr_head->next == NULL)) {
/* Empty or single record list */
return;
}
do {
rr_prev = NULL;
rr_current = rr_head;
rr_next = rr_head->next;
swap = 0;
while (rr_next != NULL) {
/*
* RFC2052: A client MUST attempt to contact the target host
* with the lowest-numbered priority it can reach.
* RFC2052: When selecting a target host among the
* those that have the same priority, the chance of trying
* this one first SHOULD be proportional to its weight.
*/
if ((rr_current->priority > rr_next->priority) ||
(rr_current->priority == rr_next->priority &&
rr_current->weight < rr_next->weight))
{
/* Swap node */
swap = 1;
if (rr_prev != NULL) {
rr_prev->next = rr_next;
} else {
/* Swap head node */
rr_head = rr_next;
}
rr_current->next = rr_next->next;
rr_next->next = rr_current;
rr_prev = rr_next;
rr_next = rr_current->next;
} else {
/* Next node */
rr_prev = rr_current;
rr_current = rr_next;
rr_next = rr_next->next;
}
}
} while (swap != 0);
*srv_rr_list = rr_head;
}
int resolver_srv_lookup_buf(xmpp_ctx_t *ctx, const unsigned char *buf,
size_t len, resolver_srv_rr_t **srv_rr_list)
{
unsigned i;
unsigned j;
unsigned name_len;
unsigned rdlength;
uint16_t type;
uint16_t class;
struct message_header header;
resolver_srv_rr_t *rr;
*srv_rr_list = NULL;
if (len < MESSAGE_HEADER_LEN)
return XMPP_DOMAIN_NOT_FOUND;
header.id = xmpp_ntohs_ptr(&buf[0]);
header.octet2 = buf[2];
header.octet3 = buf[3];
header.qdcount = xmpp_ntohs_ptr(&buf[4]);
header.ancount = xmpp_ntohs_ptr(&buf[6]);
header.nscount = xmpp_ntohs_ptr(&buf[8]);
header.arcount = xmpp_ntohs_ptr(&buf[10]);
if (message_header_qr(&header) != MESSAGE_RESPONSE ||
message_header_rcode(&header) != 0)
{
return XMPP_DOMAIN_NOT_FOUND;
}
j = MESSAGE_HEADER_LEN;
/* skip question section */
for (i = 0; i < header.qdcount; ++i) {
name_len = message_name_len(buf, len, j);
if (name_len == 0) {
/* error in name format */
return XMPP_DOMAIN_NOT_FOUND;
}
j += name_len + 4;
}
for (i = 0; i < header.ancount; ++i) {
name_len = message_name_len(buf, len, j);
j += name_len;
type = xmpp_ntohs_ptr(&buf[j]);
class = xmpp_ntohs_ptr(&buf[j + 2]);
rdlength = xmpp_ntohs_ptr(&buf[j + 8]);
j += 10;
if (type == MESSAGE_T_SRV && class == MESSAGE_C_IN) {
rr = xmpp_alloc(ctx, sizeof(*rr));
rr->next = *srv_rr_list;
rr->priority = xmpp_ntohs_ptr(&buf[j]);
rr->weight = xmpp_ntohs_ptr(&buf[j + 2]);
rr->port = xmpp_ntohs_ptr(&buf[j + 4]);
name_len = message_name_get(buf, len, j + 6, rr->target,
sizeof(rr->target));
if (name_len > 0)
*srv_rr_list = rr;
else
xmpp_free(ctx, rr); /* skip broken record */
}
j += rdlength;
}
resolver_srv_list_sort(srv_rr_list);
return *srv_rr_list != NULL ? XMPP_DOMAIN_FOUND : XMPP_DOMAIN_NOT_FOUND;
}
int resolver_srv_lookup(xmpp_ctx_t *ctx, const char *service, const char *proto,
const char *domain, resolver_srv_rr_t **srv_rr_list)
{
char fulldomain[2048];
unsigned char buf[65535];
int len;
int set = XMPP_DOMAIN_NOT_FOUND;
xmpp_snprintf(fulldomain, sizeof(fulldomain),
"_%s._%s.%s", service, proto, domain);
*srv_rr_list = NULL;
#ifdef _WIN32
set = resolver_win32_srv_lookup(ctx, fulldomain, srv_rr_list);
if (set == XMPP_DOMAIN_FOUND)
return set;
len = resolver_win32_srv_query(fulldomain, buf, sizeof(buf));
#else /* _WIN32 */
len = res_query(fulldomain, MESSAGE_C_IN, MESSAGE_T_SRV, buf, sizeof(buf));
#endif /* _WIN32 */
if (len > 0)
set = resolver_srv_lookup_buf(ctx, buf, (size_t)len, srv_rr_list);
return set;
}
void resolver_srv_free(xmpp_ctx_t *ctx, resolver_srv_rr_t *srv_rr_list)
{
resolver_srv_rr_t *rr;
while (srv_rr_list != NULL) {
rr = srv_rr_list->next;
xmpp_free(ctx, srv_rr_list);
srv_rr_list = rr;
}
}
#ifdef _WIN32
/*******************************************************************************
* Next part was copied from sock.c and contains old win32 code.
*
* The idea is to get raw response from a name server and pass it to
* resolver_srv_lookup_buf(). In fact, resolver_win32_srv_query() replaces
* the call of res_query().
* Dnsapi code is moved to a separated function resolver_srv_win32_lookup() and
* changed to meet new API.
*
* XXX If the code is compiled it should work like before.
******************************************************************************/
#include <winsock2.h>
#include <ws2tcpip.h>
#include <windns.h>
#include <Iphlpapi.h>
struct dnsquery_header
{
unsigned short id;
unsigned char qr;
unsigned char opcode;
unsigned char aa;
unsigned char tc;
unsigned char rd;
unsigned char ra;
unsigned char z;
unsigned char rcode;
unsigned short qdcount;
unsigned short ancount;
unsigned short nscount;
unsigned short arcount;
};
struct dnsquery_question
{
char qname[1024];
unsigned short qtype;
unsigned short qclass;
};
static void netbuf_add_16bitnum(unsigned char *buf, int buflen, int *offset, unsigned short num)
{
unsigned char *start = buf + *offset;
unsigned char *p = start;
/* assuming big endian */
*p++ = (num >> 8) & 0xff;
*p++ = (num) & 0xff;
*offset += 2;
}
static void netbuf_add_domain_name(unsigned char *buf, int buflen, int *offset,
char *name)
{
unsigned char *start = buf + *offset;
unsigned char *p = start;
unsigned char *wordstart, *wordend;
wordstart = (unsigned char *)name;
while (*wordstart)
{
int len;
wordend = wordstart;
while (*wordend && *wordend != '.')
{
wordend++;
}
len = (int)(wordend - wordstart);
if (len > 0x3F)
{
len = 0x3F;
}
*p++ = len;
while (wordstart != wordend)
{
*p++ = *wordstart++;
}
if (*wordstart == '.')
{
wordstart++;
}
}
*p++ = '\0';
*offset += p - start;
}
static void netbuf_add_dnsquery_header(unsigned char *buf, int buflen, int *offset, struct dnsquery_header *header)
{
unsigned char *p;
netbuf_add_16bitnum(buf, buflen, offset, header->id);
p = buf + *offset;
*p++ = ((header->qr & 0x01) << 7)
| ((header->opcode & 0x0F) << 3)
| ((header->aa & 0x01) << 2)
| ((header->tc & 0x01) << 1)
| ((header->rd & 0x01));
*p++ = ((header->ra & 0x01) << 7)
| ((header->z & 0x07) << 4)
| ((header->rcode & 0x0F));
*offset += 2;
netbuf_add_16bitnum(buf, buflen, offset, header->qdcount);
netbuf_add_16bitnum(buf, buflen, offset, header->ancount);
netbuf_add_16bitnum(buf, buflen, offset, header->nscount);
netbuf_add_16bitnum(buf, buflen, offset, header->arcount);
}
static void netbuf_add_dnsquery_question(unsigned char *buf, int buflen, int *offset, struct dnsquery_question *question)
{
netbuf_add_domain_name(buf, buflen, offset, question->qname);
netbuf_add_16bitnum(buf, buflen, offset, question->qtype);
netbuf_add_16bitnum(buf, buflen, offset, question->qclass);
}
static int resolver_win32_srv_lookup(xmpp_ctx_t *ctx, const char *fulldomain,
resolver_srv_rr_t **srv_rr_list)
{
resolver_srv_rr_t *rr;
HINSTANCE hdnsapi = NULL;
DNS_STATUS (WINAPI * pDnsQuery_A)(PCSTR, WORD, DWORD, PIP4_ARRAY, PDNS_RECORD*, PVOID*);
void (WINAPI * pDnsRecordListFree)(PDNS_RECORD, DNS_FREE_TYPE);
if (hdnsapi = LoadLibrary("dnsapi.dll")) {
pDnsQuery_A = (void *)GetProcAddress(hdnsapi, "DnsQuery_A");
pDnsRecordListFree = (void *)GetProcAddress(hdnsapi, "DnsRecordListFree");
if (pDnsQuery_A && pDnsRecordListFree) {
PDNS_RECORD dnsrecords = NULL;
DNS_STATUS error;
error = pDnsQuery_A(fulldomain, DNS_TYPE_SRV, DNS_QUERY_STANDARD, NULL, &dnsrecords, NULL);
if (error == 0) {
PDNS_RECORD current = dnsrecords;
while (current) {
if (current->wType == DNS_TYPE_SRV) {
rr = xmpp_alloc(ctx, sizeof(*rr));
if (rr == NULL)
break;
rr->next = *srv_rr_list;
rr->port = current->Data.Srv.wPort;
rr->priority = current->Data.Srv.wPriority;
rr->weight = current->Data.Srv.wWeight;
xmpp_snprintf(rr->target, sizeof(rr->target), "%s",
current->Data.Srv.pNameTarget);
*srv_rr_list = rr;
}
current = current->pNext;
}
}
pDnsRecordListFree(dnsrecords, DnsFreeRecordList);
}
FreeLibrary(hdnsapi);
}
resolver_srv_list_sort(srv_rr_list);
return *srv_rr_list != NULL ? XMPP_DOMAIN_FOUND : XMPP_DOMAIN_NOT_FOUND;
}
static int resolver_win32_srv_query(const char *fulldomain,
unsigned char *buf, size_t len)
{
int set = 0;
int insize;
/* if dnsapi didn't work/isn't there, try querying the dns server manually */
if (!set)
{
struct dnsquery_header header;
struct dnsquery_question question;
int offset = 0;
int addrlen;
sock_t sock;
struct sockaddr_in dnsaddr;
char dnsserverips[16][256];
int numdnsservers = 0;
int j;
/* Try getting the DNS server ips from GetNetworkParams() in iphlpapi first */
if (!numdnsservers)
{
HINSTANCE hiphlpapi = NULL;
DWORD (WINAPI * pGetNetworkParams)(PFIXED_INFO, PULONG);
if (hiphlpapi = LoadLibrary("Iphlpapi.dll"))
{
pGetNetworkParams = (void *)GetProcAddress(hiphlpapi, "GetNetworkParams");
if (pGetNetworkParams)
{
FIXED_INFO *fi;
ULONG len;
DWORD error;
char buffer[65535];
len = 65535;
fi = buffer;
if ((error = pGetNetworkParams(fi, &len)) == ERROR_SUCCESS)
{
IP_ADDR_STRING *pias = &(fi->DnsServerList);
while (pias && numdnsservers < 16)
{
strcpy(dnsserverips[numdnsservers++], pias->IpAddress.String);
pias = pias->Next;
}
}
}
}
FreeLibrary(hiphlpapi);
}
/* Next, try getting the DNS server ips from the registry */
if (!numdnsservers)
{
HKEY search;
LONG error;
error = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters", 0, KEY_READ, &search);
if (error != ERROR_SUCCESS)
{
error = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\VxD\\MSTCP", 0, KEY_READ, &search);
}
if (error == ERROR_SUCCESS)
{
char name[512];
DWORD len = 512;
error = RegQueryValueEx(search, "NameServer", NULL, NULL, (LPBYTE)name, &len);
if (error != ERROR_SUCCESS)
{
error = RegQueryValueEx(search, "DhcpNameServer", NULL, NULL, (LPBYTE)name, &len);
}
if (error == ERROR_SUCCESS)
{
char *parse = "0123456789.", *start, *end;
start = name;
end = name;
name[len] = '\0';
while (*start && numdnsservers < 16)
{
while (strchr(parse, *end))
{
end++;
}
strncpy(dnsserverips[numdnsservers++], start, end - start);
while (*end && !strchr(parse, *end))
{
end++;
}
start = end;
}
}
}
RegCloseKey(search);
}
if (!numdnsservers)
{
HKEY searchlist;
LONG error;
error = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces", 0, KEY_READ, &searchlist);
if (error == ERROR_SUCCESS)
{
unsigned int i;
DWORD numinterfaces = 0;
RegQueryInfoKey(searchlist, NULL, NULL, NULL, &numinterfaces, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
for (i = 0; i < numinterfaces; i++)
{
char name[512];
DWORD len = 512;
HKEY searchentry;
RegEnumKeyEx(searchlist, i, (LPTSTR)name, &len, NULL, NULL, NULL, NULL);
if (RegOpenKeyEx(searchlist, name, 0, KEY_READ, &searchentry) == ERROR_SUCCESS)
{
if (RegQueryValueEx(searchentry, "DhcpNameServer", NULL, NULL, (LPBYTE)name, &len) == ERROR_SUCCESS)
{
char *parse = "0123456789.", *start, *end;
start = name;
end = name;
name[len] = '\0';
while (*start && numdnsservers < 16)
{
while (strchr(parse, *end))
{
end++;
}
strncpy(dnsserverips[numdnsservers++], start, end - start);
while (*end && !strchr(parse, *end))
{
end++;
}
start = end;
}
}
else if (RegQueryValueEx(searchentry, "NameServer", NULL, NULL, (LPBYTE)name, &len) == ERROR_SUCCESS)
{
char *parse = "0123456789.", *start, *end;
start = name;
end = name;
name[len] = '\0';
while (*start && numdnsservers < 16)
{
while (strchr(parse, *end))
{
end++;
}
strncpy(dnsserverips[numdnsservers++], start, end - start);
while (*end && !strchr(parse, *end))
{
end++;
}
start = end;
}
}
RegCloseKey(searchentry);
}
}
RegCloseKey(searchlist);
}
}
/* If we have a DNS server, use it */
if (numdnsservers)
{
ULONG nonblocking = 1;
int i;
memset(&header, 0, sizeof(header));
header.id = 12345; /* FIXME: Get a better id here */
header.rd = 1;
header.qdcount = 1;
netbuf_add_dnsquery_header(buf, len, &offset, &header);
memset(&question, 0, sizeof(question));
strncpy(question.qname, fulldomain, 1024);
question.qtype = 33; /* SRV */
question.qclass = 1; /* INTERNET! */
netbuf_add_dnsquery_question(buf, len, &offset, &question);
insize = 0;
for (i = 0; i < numdnsservers && insize <= 0; i++)
{
sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
ioctlsocket(sock, FIONBIO, &nonblocking);
memset(&dnsaddr, 0, sizeof(dnsaddr));
dnsaddr.sin_family = AF_INET;
dnsaddr.sin_port = htons(53);
dnsaddr.sin_addr.s_addr = inet_addr(dnsserverips[i]);
addrlen = sizeof(dnsaddr);
sendto(sock, (char *)buf, offset, 0, (struct sockaddr *)&dnsaddr, addrlen);
for (j = 0; j < 50; j++)
{
insize = recvfrom(sock, (char *)buf, len, 0, (struct sockaddr *)&dnsaddr, &addrlen);
if (insize == SOCKET_ERROR)
{
if (sock_error() == WSAEWOULDBLOCK)
{
Sleep(100);
}
else
{
break;
}
}
else
{
break;
}
}
closesocket(sock);
}
set = insize > 0;
}
}
return set ? insize : -1;
}
#endif /* _WIN32 */
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