/* * Copyright (c) 2009, Rambler media * Copyright (c) 2008, 2009, 2010 William Ahern * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY Rambler media ''AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL Rambler BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * Rspamd resolver library is based on code written by William Ahern. * * The original library can be found at: http://25thandclement.com/~william/projects/dns.c.html */ #include "config.h" #include "dns.h" #include "main.h" /* Upstream timeouts */ #define DEFAULT_UPSTREAM_ERROR_TIME 10 #define DEFAULT_UPSTREAM_DEAD_TIME 300 #define DEFAULT_UPSTREAM_MAXERRORS 10 #ifdef HAVE_ARC4RANDOM #define DNS_RANDOM arc4random #elif defined HAVE_RANDOM #define DNS_RANDOM random #else #define DNS_RANDOM rand #endif /* * P E R M U T A T I O N G E N E R A T O R */ #define DNS_K_TEA_BLOCK_SIZE 8 #define DNS_K_TEA_CYCLES 32 #define DNS_K_TEA_MAGIC 0x9E3779B9U static void dns_retransmit_handler (int fd, short what, void *arg); static void dns_k_tea_init(struct dns_k_tea *tea, uint32_t key[], unsigned cycles) { memcpy(tea->key, key, sizeof tea->key); tea->cycles = (cycles)? cycles : DNS_K_TEA_CYCLES; } /* dns_k_tea_init() */ static void dns_k_tea_encrypt (struct dns_k_tea *tea, uint32_t v[], uint32_t *w) { guint32 y, z, sum, n; y = v[0]; z = v[1]; sum = 0; for (n = 0; n < tea->cycles; n++) { sum += DNS_K_TEA_MAGIC; y += ((z << 4) + tea->key[0]) ^ (z + sum) ^ ((z >> 5) + tea->key[1]); z += ((y << 4) + tea->key[2]) ^ (y + sum) ^ ((y >> 5) + tea->key[3]); } w[0] = y; w[1] = z; } /* dns_k_tea_encrypt() */ /* * Permutation generator, based on a Luby-Rackoff Feistel construction. * * Specifically, this is a generic balanced Feistel block cipher using TEA * (another block cipher) as the pseudo-random function, F. At best it's as * strong as F (TEA), notwithstanding the seeding. F could be AES, SHA-1, or * perhaps Bernstein's Salsa20 core; I am naively trying to keep things * simple. * * The generator can create a permutation of any set of numbers, as long as * the size of the set is an even power of 2. This limitation arises either * out of an inherent property of balanced Feistel constructions, or by my * own ignorance. I'll tackle an unbalanced construction after I wrap my * head around Schneier and Kelsey's paper. * * CAVEAT EMPTOR. IANAC. */ #define DNS_K_PERMUTOR_ROUNDS 8 static inline unsigned int dns_k_permutor_powof (unsigned int n) { unsigned int m, i = 0; for (m = 1; m < n; m <<= 1, i++); return i; } /* dns_k_permutor_powof() */ static void dns_k_permutor_init (struct dns_k_permutor *p, unsigned low, unsigned high) { uint32_t key[DNS_K_TEA_KEY_SIZE / sizeof (uint32_t)]; unsigned width, i; p->stepi = 0; p->length = (high - low) + 1; p->limit = high; width = dns_k_permutor_powof (p->length); width += width % 2; p->shift = width / 2; p->mask = (1U << p->shift) - 1; p->rounds = DNS_K_PERMUTOR_ROUNDS; for (i = 0; i < G_N_ELEMENTS (key); i++) { key[i] = DNS_RANDOM (); } dns_k_tea_init (&p->tea, key, 0); } /* dns_k_permutor_init() */ static unsigned dns_k_permutor_F (struct dns_k_permutor *p, unsigned k, unsigned x) { uint32_t in[DNS_K_TEA_BLOCK_SIZE / sizeof (uint32_t)], out[DNS_K_TEA_BLOCK_SIZE / sizeof (uint32_t)]; memset(in, '\0', sizeof in); in[0] = k; in[1] = x; dns_k_tea_encrypt (&p->tea, in, out); return p->mask & out[0]; } /* dns_k_permutor_F() */ static unsigned dns_k_permutor_E (struct dns_k_permutor *p, unsigned n) { unsigned l[2], r[2]; unsigned i; i = 0; l[i] = p->mask & (n >> p->shift); r[i] = p->mask & (n >> 0); do { l[(i + 1) % 2] = r[i % 2]; r[(i + 1) % 2] = l[i % 2] ^ dns_k_permutor_F(p, i, r[i % 2]); i++; } while (i < p->rounds - 1); return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0); } /* dns_k_permutor_E() */ static unsigned dns_k_permutor_D (struct dns_k_permutor *p, unsigned n) { unsigned l[2], r[2]; unsigned i; i = p->rounds - 1; l[i % 2] = p->mask & (n >> p->shift); r[i % 2] = p->mask & (n >> 0); do { i--; r[i % 2] = l[(i + 1) % 2]; l[i % 2] = r[(i + 1) % 2] ^ dns_k_permutor_F(p, i, l[(i + 1) % 2]); } while (i > 0); return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0); } /* dns_k_permutor_D() */ static unsigned dns_k_permutor_step(struct dns_k_permutor *p) { unsigned n; do { n = dns_k_permutor_E(p, p->stepi++); } while (n >= p->length); return n + (p->limit + 1 - p->length); } /* dns_k_permutor_step() */ /* * Simple permutation box. Useful for shuffling rrsets from an iterator. * Uses AES s-box to provide good diffusion. */ static unsigned short dns_k_shuffle16 (unsigned short n, unsigned s) { static const unsigned char sbox[256] = { 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; unsigned char a, b; unsigned i; a = 0xff & (n >> 0); b = 0xff & (n >> 8); for (i = 0; i < 4; i++) { a ^= 0xff & s; a = sbox[a] ^ b; b = sbox[b] ^ a; s >>= 8; } return ((0xff00 & (a << 8)) | (0x00ff & (b << 0))); } /* dns_k_shuffle16() */ struct dns_request_key { guint16 id; guint16 port; }; /** Packet creating functions */ static void allocate_packet (struct rspamd_dns_request *req, guint namelen) { namelen += 96 /* header */ + 2 /* Trailing label */ + 4; /* Resource type */ req->packet = memory_pool_alloc (req->pool, namelen); req->pos = 0; req->packet_len = namelen; } static void make_dns_header (struct rspamd_dns_request *req) { struct dns_header *header; /* Set DNS header values */ header = (struct dns_header *)req->packet; memset (header, 0 , sizeof (struct dns_header)); header->qid = dns_k_permutor_step (req->resolver->permutor); header->rd = 1; header->qdcount = 1; req->pos += sizeof (struct dns_header); req->id = header->qid; } static void format_dns_name (struct rspamd_dns_request *req, const char *name, guint namelen) { guint8 *pos = req->packet + req->pos, *begin, *end; guint remain = req->packet_len - req->pos - 5, label_len; if (namelen == 0) { namelen = strlen (name); } begin = (guint8 *)name; for (;;) { end = strchr (begin, '.'); if (end) { label_len = end - begin; if (label_len > DNS_D_MAXLABEL) { msg_err ("dns name component is longer than 63 bytes, should be stripped"); label_len = DNS_D_MAXLABEL; } if (remain < label_len + 1) { label_len = remain - 1; msg_err ("no buffer remain for constructing query, strip to %ud", label_len); } *pos++ = (guint8)label_len; memcpy (pos, begin, label_len); pos += label_len; remain -= label_len + 1; begin = end + 1; } else { end = (guint8 *)name + namelen; label_len = end - begin; if (label_len == 0) { /* If name is ended with dot */ break; } if (label_len > DNS_D_MAXLABEL) { msg_err ("dns name component is longer than 63 bytes, should be stripped"); label_len = DNS_D_MAXLABEL; } if (remain < label_len + 1) { label_len = remain - 1; msg_err ("no buffer remain for constructing query, strip to %ud", label_len); } *pos++ = (guint8)label_len; memcpy (pos, begin, label_len); pos += label_len; remain -= label_len + 1; break; } if (remain == 0) { msg_err ("no buffer space available, aborting"); break; } } /* Termination label */ *(++pos) = '\0'; req->pos += pos - (req->packet + req->pos) + 1; } static void make_ptr_req (struct rspamd_dns_request *req, struct in_addr addr) { char ipbuf[sizeof("255.255.255.255.in-addr.arpa")]; guint32 a = addr.s_addr, r; guint16 *p; r = rspamd_snprintf (ipbuf, sizeof(ipbuf), "%d.%d.%d.%d.in-addr.arpa", (int)(guint8)((a ) & 0xff), (int)(guint8)((a>>8 ) & 0xff), (int)(guint8)((a>>16) & 0xff), (int)(guint8)((a>>24) & 0xff)); allocate_packet (req, r); make_dns_header (req); format_dns_name (req, ipbuf, r); p = (guint16 *)req->packet + req->pos; *p++ = htons (DNS_C_IN); *p = htons (DNS_T_PTR); req->pos += sizeof (guint16) * 2; } static void make_a_req (struct rspamd_dns_request *req, const char *name) { guint16 *p; allocate_packet (req, strlen (name)); make_dns_header (req); format_dns_name (req, name, 0); p = (guint16 *)req->packet + req->pos; *p++ = htons (DNS_C_IN); *p = htons (DNS_T_A); req->pos += sizeof (guint16) * 2; } static void make_txt_req (struct rspamd_dns_request *req, const char *name) { guint16 *p; allocate_packet (req, strlen (name)); make_dns_header (req); format_dns_name (req, name, 0); p = (guint16 *)req->packet + req->pos; *p++ = htons (DNS_C_IN); *p = htons (DNS_T_A); req->pos += sizeof (guint16) * 2; } static void make_mx_req (struct rspamd_dns_request *req, const char *name) { guint16 *p; allocate_packet (req, strlen (name)); make_dns_header (req); format_dns_name (req, name, 0); p = (guint16 *)req->packet + req->pos; *p++ = htons (DNS_C_IN); *p = htons (DNS_T_A); req->pos += sizeof (guint16) * 2; } static int send_dns_request (struct rspamd_dns_request *req) { gint r; r = send (req->sock, req->packet, req->pos, 0); if (r == -1) { if (errno == EAGAIN) { event_set (&req->io_event, req->sock, EV_WRITE, dns_retransmit_handler, req); event_add (&req->io_event, &req->tv); register_async_event (req->session, (event_finalizer_t)event_del, &req->io_event, FALSE); return 0; } else { msg_err ("send failed: %s for server %s", strerror (errno), req->server->name); upstream_fail (&req->server->up, time (NULL)); return -1; } } else if (r < req->pos) { event_set (&req->io_event, req->sock, EV_WRITE, dns_retransmit_handler, req); event_add (&req->io_event, &req->tv); register_async_event (req->session, (event_finalizer_t)event_del, &req->io_event, FALSE); return 0; } return 1; } static void dns_fin_cb (gpointer arg) { struct rspamd_dns_request *req = arg; /* XXX: call callback if possible */ } static void dns_timer_cb (int fd, short what, void *arg) { struct rspamd_dns_request *req = arg; /* Retransmit dns request */ req->retransmits ++; if (req->retransmits >= req->resolver->max_retransmits) { msg_err ("maximum number of retransmits expired"); event_del (&req->timer_event); /* XXX: call user's callback here */ return; } /* Select other server */ req->server = (struct rspamd_dns_server *)get_upstream_round_robin (req->resolver->servers, req->resolver->servers_num, sizeof (struct rspamd_dns_server), time (NULL), DEFAULT_UPSTREAM_ERROR_TIME, DEFAULT_UPSTREAM_DEAD_TIME, DEFAULT_UPSTREAM_MAXERRORS); if (req->server == NULL) { event_del (&req->timer_event); /* XXX: call user's callback here */ return; } if (req->server->sock == -1) { req->server->sock = make_udp_socket (&req->server->addr, htons (53), FALSE, TRUE); } req->sock = req->server->sock; if (req->sock == -1) { event_del (&req->timer_event); /* XXX: call user's callback here */ return; } /* Add other retransmit event */ evtimer_add (&req->timer_event, &req->tv); } static void dns_retransmit_handler (int fd, short what, void *arg) { struct rspamd_dns_request *req = arg; gint r; if (what == EV_WRITE) { /* Retransmit dns request */ req->retransmits ++; if (req->retransmits >= req->resolver->max_retransmits) { msg_err ("maximum number of retransmits expired"); event_del (&req->io_event); /* XXX: call user's callback here */ return; } r = send_dns_request (req); if (r == -1) { event_del (&req->io_event); /* XXX: call user's callback here */ upstream_fail (&req->server->up, time (NULL)); } else if (r == 1) { /* Add timer event */ evtimer_set (&req->timer_event, dns_timer_cb, req); evtimer_add (&req->timer_event, &req->tv); /* Add request to hash table */ g_hash_table_insert (req->resolver->requests, GUINT_TO_POINTER (req->id), req); register_async_event (req->session, (event_finalizer_t)dns_fin_cb, req, FALSE); } } } gboolean make_dns_request (struct rspamd_dns_resolver *resolver, struct rspamd_async_session *session, memory_pool_t *pool, dns_callback_type cb, gpointer ud, enum rspamd_request_type type, ...) { va_list args; struct rspamd_dns_request *req; struct in_addr addr; const char *name; gint r; req = memory_pool_alloc (pool, sizeof (struct rspamd_dns_request)); req->pool = pool; req->session = session; req->resolver = resolver; req->func = cb; req->arg = ud; va_start (args, type); switch (type) { case DNS_REQUEST_PTR: addr = va_arg (args, struct in_addr); make_ptr_req (req, addr); break; case DNS_REQUEST_MX: name = va_arg (args, const char *); make_mx_req (req, name); break; case DNS_REQUEST_A: name = va_arg (args, const char *); make_a_req (req, name); break; case DNS_REQUEST_TXT: name = va_arg (args, const char *); make_txt_req (req, name); break; } va_end (args); req->retransmits = 0; req->server = (struct rspamd_dns_server *)get_upstream_round_robin (resolver->servers, resolver->servers_num, sizeof (struct rspamd_dns_server), time (NULL), DEFAULT_UPSTREAM_ERROR_TIME, DEFAULT_UPSTREAM_DEAD_TIME, DEFAULT_UPSTREAM_MAXERRORS); if (req->server == NULL) { msg_err ("cannot find suitable server for request"); return FALSE; } if (req->server->sock == -1) { req->server->sock = make_udp_socket (&req->server->addr, htons (53), FALSE, TRUE); } req->sock = req->server->sock; if (req->sock == -1) { return FALSE; } /* Fill timeout */ req->tv.tv_sec = resolver->request_timeout / 1000; req->tv.tv_usec = (resolver->request_timeout - req->tv.tv_sec * 1000) * 1000; /* Now send request to server */ r = send_dns_request (req); if (r == 1) { /* Add timer event */ evtimer_set (&req->timer_event, dns_timer_cb, req); evtimer_add (&req->timer_event, &req->tv); /* Add request to hash table */ g_hash_table_insert (resolver->requests, GUINT_TO_POINTER (req->id), req); register_async_event (session, (event_finalizer_t)dns_fin_cb, req, FALSE); } else if (r == -1) { return FALSE; } return TRUE; } #define RESOLV_CONF "/etc/resolv.conf" static gboolean parse_resolv_conf (struct rspamd_dns_resolver *resolver) { FILE *r; char buf[BUFSIZ], *p; struct rspamd_dns_server *new; struct in_addr addr; r = fopen (RESOLV_CONF, "r"); if (r == NULL) { msg_err ("cannot open %s: %s", RESOLV_CONF, strerror (errno)); return FALSE; } while (! feof (r)) { if (fgets (buf, sizeof (buf), r)) { g_strstrip (buf); if (g_ascii_strncasecmp (buf, "nameserver", sizeof ("nameserver") - 1) == 0) { p = buf + sizeof ("nameserver"); while (*p && g_ascii_isspace (*p)) { p ++; } if (! *p) { msg_warn ("cannot parse empty nameserver line in resolv.conf"); continue; } else { if (inet_aton (p, &addr) != 0) { new = &resolver->servers[resolver->servers_num]; new->name = memory_pool_strdup (resolver->static_pool, p); memcpy (&new->addr, &addr, sizeof (struct in_addr)); resolver->servers_num ++; } else { msg_warn ("cannot parse ip address of nameserver: %s", p); continue; } } } } } fclose (r); return TRUE; } struct rspamd_dns_resolver * dns_resolver_init (struct config_file *cfg) { GList *cur; struct rspamd_dns_resolver *new; char *begin, *p; int priority; struct rspamd_dns_server *serv; new = memory_pool_alloc0 (cfg->cfg_pool, sizeof (struct rspamd_dns_resolver)); new->requests = g_hash_table_new (g_direct_hash, g_direct_equal); new->permutor = memory_pool_alloc (cfg->cfg_pool, sizeof (struct dns_k_permutor)); dns_k_permutor_init (new->permutor, 0, G_MAXUINT16); new->static_pool = cfg->cfg_pool; new->request_timeout = cfg->dns_timeout; new->max_retransmits = cfg->dns_retransmits; if (cfg->nameservers == NULL) { /* Parse resolv.conf */ if (! parse_resolv_conf (new) || new->servers_num == 0) { msg_err ("cannot parse resolv.conf and no nameservers defined, so no ways to resolve addresses"); return NULL; } } else { cur = cfg->nameservers; while (cur) { begin = cur->data; p = strchr (begin, ':'); if (p != NULL) { *p = '\0'; p ++; priority = strtoul (p, NULL, 10); } else { priority = 0; } serv = &new->servers[new->servers_num]; if (inet_aton (begin, &serv->addr) != 0) { serv->name = memory_pool_strdup (new->static_pool, begin); serv->up.priority = priority; new->servers_num ++; } else { msg_warn ("cannot parse ip address of nameserver: %s", p); cur = g_list_next (cur); continue; } cur = g_list_next (cur); } if (new->servers_num == 0) { msg_err ("no valid nameservers defined, try to parse resolv.conf"); if (! parse_resolv_conf (new) || new->servers_num == 0) { msg_err ("cannot parse resolv.conf and no nameservers defined, so no ways to resolve addresses"); return NULL; } } } return new; }