/* * Copyright (c) 2009-2012, Vsevolod Stakhov * 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 AUTHOR ''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 AUTHOR 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 static const unsigned base = 36; static const unsigned t_min = 1; static const unsigned t_max = 26; static const unsigned skew = 38; static const unsigned damp = 700; static const unsigned initial_n = 128; static const unsigned initial_bias = 72; static const gint dns_port = 53; #ifdef HAVE_ARC4RANDOM #define DNS_RANDOM arc4random #elif defined HAVE_RANDOM #define DNS_RANDOM random #else #define DNS_RANDOM rand #endif #define UDP_PACKET_SIZE 4096 #define DNS_COMPRESSION_BITS 0xC0 /* Punycode utility */ static guint digit(unsigned n) { return "abcdefghijklmnopqrstuvwxyz0123456789"[n]; } static guint adapt(guint delta, guint numpoints, gint first) { guint k; if (first) { delta = delta / damp; } else { delta /= 2; } delta += delta / numpoints; k = 0; while (delta > ((base - t_min) * t_max) / 2) { delta /= base - t_min; k += base; } return k + (((base - t_min + 1) * delta) / (delta + skew)); } /** * Convert an UCS4 string to a puny-coded DNS label string suitable * when combined with delimiters and other labels for DNS lookup. * * @param in an UCS4 string to convert * @param in_len the length of in. * @param out the resulting puny-coded string. The string is not NUL * terminatied. * @param out_len before processing out_len should be the length of * the out variable, after processing it will be the length of the out * string. * * @return returns 0 on success, an wind error code otherwise * @ingroup wind */ gboolean punycode_label_toascii(const gunichar *in, gsize in_len, gchar *out, gsize *out_len) { guint n = initial_n; guint delta = 0; guint bias = initial_bias; guint h = 0; guint b; guint i; guint o = 0; guint m; for (i = 0; i < in_len; ++i) { if (in[i] < 0x80) { ++h; if (o >= *out_len) { return FALSE; } out[o++] = in[i]; } } b = h; if (b > 0) { if (o >= *out_len) { return FALSE; } out[o++] = 0x2D; } /* is this string punycoded */ if (h < in_len) { if (o + 4 >= *out_len) { return FALSE; } memmove (out + 4, out, o); memcpy (out, "xn--", 4); o += 4; } while (h < in_len) { m = (guint) -1; for (i = 0; i < in_len; ++i) { if (in[i] < m && in[i] >= n) { m = in[i]; } } delta += (m - n) * (h + 1); n = m; for (i = 0; i < in_len; ++i) { if (in[i] < n) { ++delta; } else if (in[i] == n) { guint q = delta; guint k; for (k = base;; k += base) { guint t; if (k <= bias) { t = t_min; } else if (k >= bias + t_max) { t = t_max; } else { t = k - bias; } if (q < t) { break; } if (o >= *out_len) { return -1; } out[o++] = digit (t + ((q - t) % (base - t))); q = (q - t) / (base - t); } if (o >= *out_len) { return -1; } out[o++] = digit (q); /* output */ bias = adapt (delta, h + 1, h == b); delta = 0; ++h; } } ++delta; ++n; } *out_len = o; return TRUE; } /* * 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 (gint fd, short what, void *arg); static void dns_k_tea_init(struct dns_k_tea *tea, guint32 key[], guint 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, guint32 v[], guint32 *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 guint dns_k_permutor_powof (guint n) { guint 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, guint low, guint high) { guint32 key[DNS_K_TEA_KEY_SIZE / sizeof (guint32)]; guint 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 guint dns_k_permutor_F (struct dns_k_permutor *p, guint k, guint x) { guint32 in[DNS_K_TEA_BLOCK_SIZE / sizeof (guint32)], out[DNS_K_TEA_BLOCK_SIZE / sizeof (guint32)]; 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 guint dns_k_permutor_E (struct dns_k_permutor *p, guint n) { guint l[2], r[2]; guint 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 guint dns_k_permutor_D (struct dns_k_permutor *p, guint n) { guint l[2], r[2]; guint 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 guint dns_k_permutor_step(struct dns_k_permutor *p) { guint 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 guint16 dns_k_shuffle16 (guint16 n, guint s) { static const guint8 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 }; guchar a, b; guint 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; }; /** Message compression */ struct dns_name_table { guint8 off; guint8 *label; guint8 len; }; static gboolean try_compress_label (memory_pool_t *pool, guint8 *target, guint8 *start, guint8 len, guint8 *label, GList **table) { GList *cur; struct dns_name_table *tbl; guint16 pointer; cur = *table; while (cur) { tbl = cur->data; if (tbl->len == len) { if (memcmp (label, tbl->label, len) == 0) { pointer = htons ((guint16)tbl->off | 0xC0); memcpy (target, &pointer, sizeof (pointer)); return TRUE; } } cur = g_list_next (cur); } /* Insert label to list */ tbl = memory_pool_alloc (pool, sizeof (struct dns_name_table)); tbl->off = target - start; tbl->label = label; tbl->len = len; *table = g_list_prepend (*table, tbl); return FALSE; } /** 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 = htons (1); req->pos += sizeof (struct dns_header); req->id = header->qid; } static gboolean maybe_punycode_label (guint8 *begin, guint8 **res, guint8 **dot, guint *label_len) { gboolean ret = FALSE; guint8 *p = begin; *dot = NULL; while (*p) { if (*p == '.') { *dot = p; break; } else if ((*p) & 0x80) { ret = TRUE; } p ++; } if (*p) { *res = p - 1; *label_len = p - begin; } else { *res = p; *label_len = p - begin; } return ret; } static void format_dns_name (struct rspamd_dns_request *req, const gchar *name, guint namelen) { guint8 *pos = req->packet + req->pos, *end, *dot, *name_pos, *begin; guint remain = req->packet_len - req->pos - 5, label_len; GList *table = NULL; gunichar *uclabel; glong uclabel_len; gsize punylabel_len; guint8 tmp_label[DNS_D_MAXLABEL]; if (namelen == 0) { namelen = strlen (name); } begin = (guint8 *)name; end = (guint8 *)name + namelen; for (;;) { /* Check label for unicode characters */ if (maybe_punycode_label (begin, &name_pos, &dot, &label_len)) { /* Convert to ucs4 */ uclabel = g_utf8_to_ucs4_fast ((gchar *)begin, label_len, &uclabel_len); memory_pool_add_destructor (req->pool, g_free, uclabel); punylabel_len = DNS_D_MAXLABEL; punycode_label_toascii (uclabel, uclabel_len, (gchar *)tmp_label, &punylabel_len); /* Try to compress name */ if (! try_compress_label (req->pool, pos, req->packet, punylabel_len, tmp_label, &table)) { /* Copy punylabel */ *pos++ = (guint8)punylabel_len; memcpy (pos, tmp_label, punylabel_len); pos += punylabel_len; } else { pos += 2; } if (dot) { remain -= label_len + 1; begin = dot + 1; } else { break; } } else { if (dot) { 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); } if (label_len == 0) { /* Two dots in order, skip this */ msg_info ("name contains two or more dots in a row, replace it with one dot"); begin = dot + 1; continue; } /* First try to compress name */ if (! try_compress_label (req->pool, pos, req->packet, end - begin, begin, &table)) { *pos++ = (guint8)label_len; memcpy (pos, begin, label_len); pos += label_len; } else { pos += 2; } remain -= label_len + 1; begin = dot + 1; } else { 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; break; } } if (remain == 0) { msg_err ("no buffer space available, aborting"); break; } } /* Termination label */ *pos = '\0'; req->pos += pos - (req->packet + req->pos) + 1; if (table != NULL) { g_list_free (table); } } static void make_ptr_req (struct rspamd_dns_request *req, struct in_addr *addr) { gchar ipbuf[sizeof("255.255.255.255.in-addr.arpa")]; guint32 r; guint16 *p; guint8 *addr_p = (guint8 *)&addr->s_addr; r = rspamd_snprintf (ipbuf, sizeof(ipbuf), "%d.%d.%d.%d.in-addr.arpa", addr_p[3], addr_p[2], addr_p[1], addr_p[0]); allocate_packet (req, r); make_dns_header (req); format_dns_name (req, ipbuf, r); p = (guint16 *)(req->packet + req->pos); *p++ = htons (DNS_T_PTR); *p = htons (DNS_C_IN); req->requested_name = memory_pool_strdup (req->pool, ipbuf); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_PTR; } static void make_a_req (struct rspamd_dns_request *req, const gchar *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_T_A); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_A; req->requested_name = name; } #ifdef HAVE_INET_PTON static void make_aaa_req (struct rspamd_dns_request *req, const gchar *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_T_AAAA); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_AAA; req->requested_name = name; } #endif static void make_txt_req (struct rspamd_dns_request *req, const gchar *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_T_TXT); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_TXT; req->requested_name = name; } static void make_mx_req (struct rspamd_dns_request *req, const gchar *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_T_MX); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_MX; req->requested_name = name; } static void make_srv_req (struct rspamd_dns_request *req, const gchar *service, const gchar *proto, const gchar *name) { guint16 *p; guint len; gchar *target; len = strlen (service) + strlen (proto) + strlen (name) + 5; allocate_packet (req, len); make_dns_header (req); target = memory_pool_alloc (req->pool, len); len = rspamd_snprintf (target, len, "_%s._%s.%s", service, proto, name); format_dns_name (req, target, len); p = (guint16 *)(req->packet + req->pos); *p++ = htons (DNS_T_SRV); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_SRV; req->requested_name = name; } static void make_spf_req (struct rspamd_dns_request *req, const gchar *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_T_SPF); *p = htons (DNS_C_IN); req->pos += sizeof (guint16) * 2; req->type = DNS_REQUEST_SPF; req->requested_name = name; } static gint 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_base_set (req->resolver->ev_base, &req->io_event); event_add (&req->io_event, &req->tv); register_async_event (req->session, (event_finalizer_t)event_del, &req->io_event, g_quark_from_static_string ("dns resolver")); return 0; } else { msg_err ("send failed: %s for server %s", strerror (errno), req->server->name); upstream_fail (&req->server->up, req->time); return -1; } } else if (r < req->pos) { event_set (&req->io_event, req->sock, EV_WRITE, dns_retransmit_handler, req); event_base_set (req->resolver->ev_base, &req->io_event); event_add (&req->io_event, &req->tv); register_async_event (req->session, (event_finalizer_t)event_del, &req->io_event, g_quark_from_static_string ("dns resolver")); return 0; } return 1; } static void dns_fin_cb (gpointer arg) { struct rspamd_dns_request *req = arg; event_del (&req->timer_event); g_hash_table_remove (req->resolver->requests, &req->id); } static guint8 * decompress_label (guint8 *begin, guint16 *len, guint16 max) { guint16 offset = DNS_COMPRESSION_BITS; offset = (*len) ^ (offset << 8); if (offset > max) { return NULL; } *len = *(begin + offset); return begin + offset; } static guint8 * dns_request_reply_cmp (struct rspamd_dns_request *req, guint8 *in, gint len) { guint8 *p, *c, *l1, *l2; guint16 len1, len2; gint decompressed = 0; /* QR format: * labels - len:octets * null label - 0 * class - 2 octets * type - 2 octets */ /* In p we would store current position in reply and in c - position in request */ p = in; c = req->packet + sizeof (struct dns_header); for (;;) { /* Get current label */ len1 = *p; len2 = *c; if (p - in > len) { msg_info ("invalid dns reply"); return NULL; } /* This may be compressed, so we need to decompress it */ if (len1 & DNS_COMPRESSION_BITS) { len1 = ((*p) << 8) + *(p + 1); l1 = decompress_label (in, &len1, len); if (l1 == NULL) { msg_info ("invalid DNS pointer"); return NULL; } decompressed ++; l1 ++; p += 2; } else { l1 = ++p; p += len1; } if (len2 & DNS_COMPRESSION_BITS) { len2 = ((*p) << 8) + *(p + 1); l2 = decompress_label (req->packet, &len2, len); if (l2 == NULL) { msg_info ("invalid DNS pointer"); return NULL; } decompressed ++; l2 ++; c += 2; } else { l2 = ++c; c += len2; } if (len1 != len2) { return NULL; } if (len1 == 0) { break; } if (memcmp (l1, l2, len1) != 0) { return NULL; } if (decompressed == 2) { break; } } /* p now points to the end of QR section */ /* Compare class and type */ if (memcmp (p, c, sizeof (guint16) * 2) == 0) { return p + sizeof (guint16) * 2; } return NULL; } #define MAX_RECURSION_LEVEL 10 static gboolean dns_parse_labels (guint8 *in, gchar **target, guint8 **pos, struct rspamd_dns_reply *rep, gint *remain, gboolean make_name) { guint16 namelen = 0; guint8 *p = *pos, *begin = *pos, *l, *t, *end = *pos + *remain; guint16 llen; gint offset = -1; gint length = *remain; gint ptrs = 0, labels = 0; /* First go through labels and calculate name length */ while (p - begin < length) { if (ptrs > MAX_RECURSION_LEVEL) { msg_warn ("dns pointers are nested too much"); return FALSE; } llen = *p; if (llen == 0) { break; } else if (llen & DNS_COMPRESSION_BITS) { ptrs ++; llen = ((*p) << 8) + *(p + 1); l = decompress_label (in, &llen, end - in); if (l == NULL) { msg_info ("invalid DNS pointer"); return FALSE; } if (offset < 0) { /* Set offset strictly */ offset = p - begin + 2; } if (l < in || l > begin + length) { msg_warn ("invalid pointer in DNS packet"); return FALSE; } begin = l; length = end - begin; p = l + *l + 1; namelen += *l; labels ++; } else { namelen += *p; p += *p + 1; labels ++; } } if (!make_name) { goto end; } *target = memory_pool_alloc (rep->request->pool, namelen + labels + 3); t = (guint8 *)*target; p = *pos; begin = *pos; length = *remain; /* Now copy labels to name */ while (p - begin < length) { llen = *p; if (llen == 0) { break; } else if (llen & DNS_COMPRESSION_BITS) { llen = ((*p) << 8) + *(p + 1); l = decompress_label (in, &llen, end - in); begin = l; length = end - begin; p = l + *l + 1; memcpy (t, l + 1, *l); t += *l; *t ++ = '.'; } else { memcpy (t, p + 1, *p); t += *p; *t ++ = '.'; p += *p + 1; } } *(t - 1) = '\0'; end: if (offset < 0) { offset = p - begin + 1; } *remain -= offset; *pos += offset; return TRUE; } #define GET16(x) do {(x) = ((*p) << 8) + *(p + 1); p += sizeof (guint16); *remain -= sizeof (guint16); } while(0) #define GET32(x) do {(x) = ((*p) << 24) + ((*(p + 1)) << 16) + ((*(p + 2)) << 8) + *(p + 3); p += sizeof (guint32); *remain -= sizeof (guint32); } while(0) static gint dns_parse_rr (guint8 *in, union rspamd_reply_element *elt, guint8 **pos, struct rspamd_dns_reply *rep, gint *remain) { guint8 *p = *pos, parts; guint16 type, datalen, txtlen, copied; gboolean parsed = FALSE; /* Skip the whole name */ if (! dns_parse_labels (in, NULL, &p, rep, remain, FALSE)) { msg_info ("bad RR name"); return -1; } if ((gint)(p - *pos) >= (gint)(*remain - sizeof (guint16) * 5) || *remain <= 0) { msg_info ("stripped dns reply"); return -1; } GET16 (type); /* Skip ttl and class */ p += sizeof (guint16) + sizeof (guint32); *remain -= sizeof (guint16) + sizeof (guint32); GET16 (datalen); /* Now p points to RR data */ switch (type) { case DNS_T_A: if (rep->request->type != DNS_REQUEST_A) { p += datalen; } else { if (!(datalen & 0x3) && datalen <= *remain) { memcpy (&elt->a.addr[0], p, sizeof (struct in_addr)); p += datalen; parsed = TRUE; } else { msg_info ("corrupted A record"); return -1; } } break; #ifdef HAVE_INET_PTON case DNS_T_AAAA: if (rep->request->type != DNS_REQUEST_AAA) { p += datalen; } else { if (datalen == sizeof (struct in6_addr) && datalen <= *remain) { memcpy (&elt->aaa.addr, p, sizeof (struct in6_addr)); p += datalen; parsed = TRUE; } else { msg_info ("corrupted AAAA record"); return -1; } } break; #endif case DNS_T_PTR: if (rep->request->type != DNS_REQUEST_PTR) { p += datalen; } else { if (! dns_parse_labels (in, &elt->ptr.name, &p, rep, remain, TRUE)) { msg_info ("invalid labels in PTR record"); return -1; } parsed = TRUE; } break; case DNS_T_MX: if (rep->request->type != DNS_REQUEST_MX) { p += datalen; } else { GET16 (elt->mx.priority); datalen -= sizeof (guint16); if (! dns_parse_labels (in, &elt->mx.name, &p, rep, remain, TRUE)) { msg_info ("invalid labels in MX record"); return -1; } parsed = TRUE; } break; case DNS_T_TXT: if (rep->request->type != DNS_REQUEST_TXT) { p += datalen; } else { elt->txt.data = memory_pool_alloc (rep->request->pool, datalen + 1); /* Now we should compose data from parts */ copied = 0; parts = 0; while (copied + parts < datalen) { txtlen = *p; if (txtlen + copied + parts <= datalen) { parts ++; memcpy (elt->txt.data + copied, p + 1, txtlen); copied += txtlen; p += txtlen + 1; } else { break; } } *(elt->txt.data + copied) = '\0'; parsed = TRUE; } break; case DNS_T_SPF: if (rep->request->type != DNS_REQUEST_SPF) { p += datalen; } else { copied = 0; elt->txt.data = memory_pool_alloc (rep->request->pool, datalen + 1); while (copied < datalen) { txtlen = *p; if (txtlen + copied < datalen) { memcpy (elt->txt.data + copied, p + 1, txtlen); copied += txtlen; p += txtlen + 1; } else { break; } } *(elt->spf.data + copied) = '\0'; parsed = TRUE; } break; case DNS_T_SRV: if (rep->request->type != DNS_REQUEST_SRV) { p += datalen; } else { if (p - *pos > (gint)(*remain - sizeof (guint16) * 3)) { msg_info ("stripped dns reply while reading SRV record"); return -1; } GET16 (elt->srv.priority); GET16 (elt->srv.weight); GET16 (elt->srv.port); if (! dns_parse_labels (in, &elt->srv.target, &p, rep, remain, TRUE)) { msg_info ("invalid labels in SRV record"); return -1; } parsed = TRUE; } break; case DNS_T_CNAME: /* Skip cname records */ p += datalen; break; default: msg_debug ("unexpected RR type: %d", type); p += datalen; break; } *remain -= datalen; *pos = p; if (parsed) { return 1; } return 0; } static gboolean dns_parse_reply (guint8 *in, gint r, struct rspamd_dns_resolver *resolver, struct rspamd_dns_request **req_out, struct rspamd_dns_reply **_rep) { struct dns_header *header = (struct dns_header *)in; struct rspamd_dns_request *req; struct rspamd_dns_reply *rep; union rspamd_reply_element *elt; guint8 *pos; guint16 id; gint i, t; /* First check header fields */ if (header->qr == 0) { msg_info ("got request while waiting for reply"); return FALSE; } /* Now try to find corresponding request */ id = header->qid; if ((req = g_hash_table_lookup (resolver->requests, &id)) == NULL) { /* No such requests found */ return FALSE; } *req_out = req; /* * Now we have request and query data is now at the end of header, so compare * request QR section and reply QR section */ if ((pos = dns_request_reply_cmp (req, in + sizeof (struct dns_header), r - sizeof (struct dns_header))) == NULL) { return FALSE; } /* * Now pos is in answer section, so we should extract data and form reply */ rep = memory_pool_alloc (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->type = req->type; rep->elements = NULL; rep->code = header->rcode; if (rep->code == DNS_RC_NOERROR) { r -= pos - in; /* Extract RR records */ for (i = 0; i < ntohs (header->ancount); i ++) { elt = memory_pool_alloc (req->pool, sizeof (union rspamd_reply_element)); t = dns_parse_rr (in, elt, &pos, rep, &r); if (t == -1) { msg_info ("incomplete reply"); break; } else if (t == 1) { rep->elements = g_list_prepend (rep->elements, elt); } } if (rep->elements) { memory_pool_add_destructor (req->pool, (pool_destruct_func)g_list_free, rep->elements); } } *_rep = rep; return TRUE; } static void dns_throttling_cb (gint fd, short what, void *arg) { struct rspamd_dns_resolver *resolver = arg; resolver->throttling = FALSE; resolver->errors = 0; msg_info ("stop DNS throttling after %d seconds", (int)resolver->throttling_time.tv_sec); event_del (&resolver->throttling_event); } static void dns_check_throttling (struct rspamd_dns_resolver *resolver) { if (resolver->errors > resolver->max_errors && !resolver->throttling) { msg_info ("starting DNS throttling after %ud errors", resolver->errors); /* Init throttling timeout */ resolver->throttling = TRUE; evtimer_set (&resolver->throttling_event, dns_throttling_cb, resolver); event_base_set (resolver->ev_base, &resolver->throttling_event); event_add (&resolver->throttling_event, &resolver->throttling_time); } } static void dns_read_cb (gint fd, short what, void *arg) { struct rspamd_dns_resolver *resolver = arg; struct rspamd_dns_request *req = NULL; gint r; struct rspamd_dns_reply *rep; guint8 in[UDP_PACKET_SIZE]; /* This function is called each time when we have data on one of server's sockets */ /* First read packet from socket */ r = read (fd, in, sizeof (in)); if (r > (gint)(sizeof (struct dns_header) + sizeof (struct dns_query))) { if (dns_parse_reply (in, r, resolver, &req, &rep)) { /* Decrease errors count */ if (rep->request->resolver->errors > 0) { rep->request->resolver->errors --; } upstream_ok (&rep->request->server->up, rep->request->time); rep->request->func (rep, rep->request->arg); remove_normal_event (req->session, dns_fin_cb, req); } } } static void dns_timer_cb (gint fd, short what, void *arg) { struct rspamd_dns_request *req = arg; struct rspamd_dns_reply *rep; gint r; /* Retransmit dns request */ req->retransmits ++; if (req->retransmits >= req->resolver->max_retransmits) { msg_err ("maximum number of retransmits expired for resolving %s of type %s", req->requested_name, dns_strtype (req->type)); rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; upstream_fail (&rep->request->server->up, rep->request->time); dns_check_throttling (req->resolver); req->resolver->errors ++; req->func (rep, req->arg); remove_normal_event (req->session, dns_fin_cb, req); return; } /* Select other server */ if (req->resolver->is_master_slave) { req->server = (struct rspamd_dns_server *)get_upstream_master_slave (req->resolver->servers, req->resolver->servers_num, sizeof (struct rspamd_dns_server), req->time, DEFAULT_UPSTREAM_ERROR_TIME, DEFAULT_UPSTREAM_DEAD_TIME, DEFAULT_UPSTREAM_MAXERRORS); } else { req->server = (struct rspamd_dns_server *)get_upstream_round_robin (req->resolver->servers, req->resolver->servers_num, sizeof (struct rspamd_dns_server), req->time, DEFAULT_UPSTREAM_ERROR_TIME, DEFAULT_UPSTREAM_DEAD_TIME, DEFAULT_UPSTREAM_MAXERRORS); } if (req->server == NULL) { rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; req->func (rep, req->arg); remove_normal_event (req->session, dns_fin_cb, req); return; } if (req->server->sock == -1) { req->server->sock = make_universal_socket (req->server->name, dns_port, SOCK_DGRAM, TRUE, FALSE, FALSE); } req->sock = req->server->sock; if (req->sock == -1) { rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; upstream_fail (&rep->request->server->up, rep->request->time); req->func (rep, req->arg); remove_normal_event (req->session, dns_fin_cb, req); return; } /* Add other retransmit event */ r = send_dns_request (req); if (r == -1) { rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; upstream_fail (&rep->request->server->up, rep->request->time); req->func (rep, req->arg); remove_normal_event (req->session, dns_fin_cb, req); return; } evtimer_add (&req->timer_event, &req->tv); } static void dns_retransmit_handler (gint fd, short what, void *arg) { struct rspamd_dns_request *req = arg; struct rspamd_dns_reply *rep; gint r; remove_normal_event (req->session, (event_finalizer_t)event_del, &req->io_event); if (what == EV_WRITE) { /* Retransmit dns request */ req->retransmits ++; event_del (&req->io_event); if (req->retransmits >= req->resolver->max_retransmits) { msg_err ("maximum number of retransmits expired for %s", req->requested_name); rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; upstream_fail (&rep->request->server->up, rep->request->time); req->resolver->errors ++; dns_check_throttling (req->resolver); req->func (rep, req->arg); return; } r = send_dns_request (req); if (r == -1) { rep = memory_pool_alloc0 (req->pool, sizeof (struct rspamd_dns_reply)); rep->request = req; rep->code = DNS_RC_SERVFAIL; upstream_fail (&rep->request->server->up, rep->request->time); req->func (rep, req->arg); } else if (r == 1) { /* Add timer event */ event_del (&req->timer_event); evtimer_set (&req->timer_event, dns_timer_cb, req); event_base_set (req->resolver->ev_base, &req->timer_event); evtimer_add (&req->timer_event, &req->tv); /* Add request to hash table */ g_hash_table_insert (req->resolver->requests, &req->id, req); register_async_event (req->session, (event_finalizer_t)dns_fin_cb, req, g_quark_from_static_string ("dns resolver")); } } } 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 gchar *name, *service, *proto; gint r; struct dns_header *header; /* Check throttling */ if (resolver->throttling) { return FALSE; } 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; req->type = type; 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 gchar *); make_mx_req (req, name); break; case DNS_REQUEST_A: name = va_arg (args, const gchar *); make_a_req (req, name); break; case DNS_REQUEST_AAA: #ifdef HAVE_INET_PTON name = va_arg (args, const gchar *); make_aaa_req (req, name); break; #else msg_err ("your system has no ipv6 support, cannot make aaa request"); break; #endif case DNS_REQUEST_TXT: name = va_arg (args, const gchar *); make_txt_req (req, name); break; case DNS_REQUEST_SPF: name = va_arg (args, const gchar *); make_spf_req (req, name); break; case DNS_REQUEST_SRV: service = va_arg (args, const gchar *); proto = va_arg (args, const gchar *); name = va_arg (args, const gchar *); make_srv_req (req, service, proto, name); break; } va_end (args); req->retransmits = 0; req->time = time (NULL); if (resolver->is_master_slave) { req->server = (struct rspamd_dns_server *)get_upstream_master_slave (resolver->servers, resolver->servers_num, sizeof (struct rspamd_dns_server), req->time, DEFAULT_UPSTREAM_ERROR_TIME, DEFAULT_UPSTREAM_DEAD_TIME, DEFAULT_UPSTREAM_MAXERRORS); } else { req->server = (struct rspamd_dns_server *)get_upstream_round_robin (resolver->servers, resolver->servers_num, sizeof (struct rspamd_dns_server), req->time, 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_universal_socket (req->server->name, dns_port, SOCK_DGRAM, TRUE, FALSE, FALSE); } req->sock = req->server->sock; if (req->sock == -1) { return FALSE; } /* Fill timeout */ msec_to_tv (resolver->request_timeout, &req->tv); evtimer_set (&req->timer_event, dns_timer_cb, req); event_base_set (req->resolver->ev_base, &req->timer_event); /* Now send request to server */ r = send_dns_request (req); if (r == 1) { /* Add timer event */ evtimer_add (&req->timer_event, &req->tv); /* Add request to hash table */ while (g_hash_table_lookup (resolver->requests, &req->id)) { /* Check for unique id */ header = (struct dns_header *)req->packet; header->qid = dns_k_permutor_step (resolver->permutor); req->id = header->qid; } g_hash_table_insert (resolver->requests, &req->id, req); register_async_event (session, (event_finalizer_t)dns_fin_cb, req, g_quark_from_static_string ("dns resolver")); } 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; gchar buf[BUFSIZ], *p, addr_holder[16]; struct rspamd_dns_server *new; 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_pton (AF_INET6, p, addr_holder) == 1 || inet_pton (AF_INET, p, addr_holder) == 1) { new = &resolver->servers[resolver->servers_num]; new->name = memory_pool_strdup (resolver->static_pool, p); resolver->servers_num ++; } else { msg_warn ("cannot parse ip address of nameserver: %s", p); continue; } } } } } fclose (r); return TRUE; } /* Hashing utilities */ static gboolean dns_id_equal (gconstpointer v1, gconstpointer v2) { return *((const guint16*) v1) == *((const guint16*) v2); } static guint dns_id_hash (gconstpointer v) { return *(const guint16 *) v; } struct rspamd_dns_resolver * dns_resolver_init (struct event_base *ev_base, struct config_file *cfg) { GList *cur; struct rspamd_dns_resolver *new; gchar *begin, *p, *err, addr_holder[16]; gint priority, i; struct rspamd_dns_server *serv; new = memory_pool_alloc0 (cfg->cfg_pool, sizeof (struct rspamd_dns_resolver)); new->ev_base = ev_base; new->requests = g_hash_table_new (dns_id_hash, dns_id_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; new->max_errors = cfg->dns_throttling_errors; msec_to_tv (cfg->dns_throttling_time, &new->throttling_time); 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 ++; if (!new->is_master_slave) { priority = strtoul (p, &err, 10); if (err != NULL && (*err == 'm' || *err == 'M' || *err == 's' || *err == 'S')) { new->is_master_slave = TRUE; } else { msg_info ("bad character '%c', must be 'm' or 's' or a numeric priority", *err); } } if (new->is_master_slave) { if (*p == 'm' || *p == 'M') { priority = 100; } else if (*p == 's' || *p == 'S') { priority = 1; } else { msg_info ("master/slave mode is turned on, and %c character is invalid", *p); priority = 0; } } } else { priority = 0; } serv = &new->servers[new->servers_num]; if (inet_pton (AF_INET6, p, addr_holder) == 1 || inet_pton (AF_INET, p, addr_holder) == 1) { 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; } } } /* Now init all servers */ for (i = 0; i < new->servers_num; i ++) { serv = &new->servers[i]; serv->sock = make_universal_socket (serv->name, dns_port, SOCK_DGRAM, TRUE, FALSE, FALSE); if (serv->sock == -1) { msg_warn ("cannot create socket to server %s", serv->name); } else { event_set (&serv->ev, serv->sock, EV_READ | EV_PERSIST, dns_read_cb, new); event_base_set (new->ev_base, &serv->ev); event_add (&serv->ev, NULL); } } return new; } static gchar dns_rcodes[16][16] = { [DNS_RC_NOERROR] = "NOERROR", [DNS_RC_FORMERR] = "FORMERR", [DNS_RC_SERVFAIL] = "SERVFAIL", [DNS_RC_NXDOMAIN] = "NXDOMAIN", [DNS_RC_NOTIMP] = "NOTIMP", [DNS_RC_REFUSED] = "REFUSED", [DNS_RC_YXDOMAIN] = "YXDOMAIN", [DNS_RC_YXRRSET] = "YXRRSET", [DNS_RC_NXRRSET] = "NXRRSET", [DNS_RC_NOTAUTH] = "NOTAUTH", [DNS_RC_NOTZONE] = "NOTZONE", }; const gchar * dns_strerror (enum dns_rcode rcode) { rcode &= 0xf; static gchar numbuf[16]; if ('\0' == dns_rcodes[rcode][0]) { rspamd_snprintf (numbuf, sizeof (numbuf), "UNKNOWN: %d", (gint)rcode); return numbuf; } return dns_rcodes[rcode]; } static gchar dns_types[7][16] = { [DNS_REQUEST_A] = "A request", [DNS_REQUEST_PTR] = "PTR request", [DNS_REQUEST_MX] = "MX request", [DNS_REQUEST_TXT] = "TXT request", [DNS_REQUEST_SRV] = "SRV request", [DNS_REQUEST_SPF] = "SPF request", [DNS_REQUEST_AAA] = "AAA request" }; const gchar * dns_strtype (enum rspamd_request_type type) { return dns_types[type]; }