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-rw-r--r--src/lookups/dnsdb.c614
1 files changed, 614 insertions, 0 deletions
diff --git a/src/lookups/dnsdb.c b/src/lookups/dnsdb.c
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+++ b/src/lookups/dnsdb.c
@@ -0,0 +1,614 @@
+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/* Copyright (c) The Exim Maintainers 2020 - 2022 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
+/* See the file NOTICE for conditions of use and distribution. */
+
+#include "../exim.h"
+#include "lf_functions.h"
+
+
+
+/* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
+header files. */
+
+#ifndef T_TXT
+# define T_TXT 16
+#endif
+
+/* Many systems do not have T_SPF. */
+#ifndef T_SPF
+# define T_SPF 99
+#endif
+
+/* New TLSA record for DANE */
+#ifndef T_TLSA
+# define T_TLSA 52
+#endif
+
+/* Table of recognized DNS record types and their integer values. */
+
+static const char *type_names[] = {
+ "a",
+#if HAVE_IPV6
+ "a+",
+ "aaaa",
+#endif
+ "cname",
+ "csa",
+ "mx",
+ "mxh",
+ "ns",
+ "ptr",
+ "soa",
+ "spf",
+ "srv",
+ "tlsa",
+ "txt",
+ "zns"
+};
+
+static int type_values[] = {
+ T_A,
+#if HAVE_IPV6
+ T_ADDRESSES, /* Private type for AAAA + A */
+ T_AAAA,
+#endif
+ T_CNAME,
+ T_CSA, /* Private type for "Client SMTP Authorization". */
+ T_MX,
+ T_MXH, /* Private type for "MX hostnames" */
+ T_NS,
+ T_PTR,
+ T_SOA,
+ T_SPF,
+ T_SRV,
+ T_TLSA,
+ T_TXT,
+ T_ZNS /* Private type for "zone nameservers" */
+};
+
+
+/*************************************************
+* Open entry point *
+*************************************************/
+
+/* See local README for interface description. */
+
+static void *
+dnsdb_open(const uschar * filename, uschar **errmsg)
+{
+return (void *)(-1); /* Any non-0 value */
+}
+
+
+
+/*************************************************
+* Find entry point for dnsdb *
+*************************************************/
+
+/* See local README for interface description. The query in the "keystring" may
+consist of a number of parts.
+
+(a) If the first significant character is '>' then the next character is the
+separator character that is used when multiple records are found. The default
+separator is newline.
+
+(b) If the next character is ',' then the next character is the separator
+character used for multiple items of text in "TXT" records. Alternatively,
+if the next character is ';' then these multiple items are concatenated with
+no separator. With neither of these options specified, only the first item
+is output. Similarly for "SPF" records, but the default for joining multiple
+items in one SPF record is the empty string, for direct concatenation.
+
+(c) Options, all comma-terminated, in any order. Any unrecognised option
+terminates option processing. Recognised options are:
+
+- 'defer_FOO': set the defer behaviour to FOO. The possible behaviours are:
+'strict', where any defer causes the whole lookup to defer; 'lax', where a defer
+causes the whole lookup to defer only if none of the DNS queries succeeds; and
+'never', where all defers are as if the lookup failed. The default is 'lax'.
+
+- 'dnssec_FOO', with 'strict', 'lax' (default), and 'never'. The meanings are
+require, try and don't-try dnssec respectively.
+
+- 'retrans_VAL', set the timeout value. VAL is an Exim time specification
+(eg "5s"). The default is set by the main configuration option 'dns_retrans'.
+
+- 'retry_VAL', set the retry count on timeouts. VAL is an integer. The
+default is set by the main configuration option "dns_retry".
+
+(d) If the next sequence of characters is a sequence of letters and digits
+followed by '=', it is interpreted as the name of the DNS record type. The
+default is "TXT".
+
+(e) Then there follows list of domain names. This is a generalized Exim list,
+which may start with '<' in order to set a specific separator. The default
+separator, as always, is colon. */
+
+static int
+dnsdb_find(void * handle, const uschar * filename, const uschar * keystring,
+ int length, uschar ** result, uschar ** errmsg, uint * do_cache,
+ const uschar * opts)
+{
+int rc;
+int sep = 0;
+int defer_mode = PASS;
+int dnssec_mode = PASS;
+int save_retrans = dns_retrans;
+int save_retry = dns_retry;
+int type;
+int failrc = FAIL;
+const uschar *outsep = CUS"\n";
+const uschar *outsep2 = NULL;
+uschar *equals, *domain, *found;
+
+dns_answer * dnsa = store_get_dns_answer();
+dns_scan dnss;
+
+/* Because we're working in the search pool, we try to reclaim as much
+store as possible later, so we preallocate the result here */
+
+gstring * yield = string_get(256);
+
+/* If the string starts with '>' we change the output separator.
+If it's followed by ';' or ',' we set the TXT output separator. */
+
+while (isspace(*keystring)) keystring++;
+if (*keystring == '>')
+ {
+ outsep = keystring + 1;
+ keystring += 2;
+ if (*keystring == ',')
+ {
+ outsep2 = keystring + 1;
+ keystring += 2;
+ }
+ else if (*keystring == ';')
+ {
+ outsep2 = US"";
+ keystring++;
+ }
+ while (isspace(*keystring)) keystring++;
+ }
+
+/* Check for a modifier keyword. */
+
+for (;;)
+ {
+ if (strncmpic(keystring, US"defer_", 6) == 0)
+ {
+ keystring += 6;
+ if (strncmpic(keystring, US"strict", 6) == 0)
+ { defer_mode = DEFER; keystring += 6; }
+ else if (strncmpic(keystring, US"lax", 3) == 0)
+ { defer_mode = PASS; keystring += 3; }
+ else if (strncmpic(keystring, US"never", 5) == 0)
+ { defer_mode = OK; keystring += 5; }
+ else
+ {
+ *errmsg = US"unsupported dnsdb defer behaviour";
+ rc = DEFER;
+ goto out;
+ }
+ }
+ else if (strncmpic(keystring, US"dnssec_", 7) == 0)
+ {
+ keystring += 7;
+ if (strncmpic(keystring, US"strict", 6) == 0)
+ { dnssec_mode = DEFER; keystring += 6; }
+ else if (strncmpic(keystring, US"lax", 3) == 0)
+ { dnssec_mode = PASS; keystring += 3; }
+ else if (strncmpic(keystring, US"never", 5) == 0)
+ { dnssec_mode = OK; keystring += 5; }
+ else
+ {
+ *errmsg = US"unsupported dnsdb dnssec behaviour";
+ rc = DEFER;
+ goto out;
+ }
+ }
+ else if (strncmpic(keystring, US"retrans_", 8) == 0)
+ {
+ int timeout_sec;
+ if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
+ {
+ *errmsg = US"unsupported dnsdb timeout value";
+ rc = DEFER;
+ goto out;
+ }
+ dns_retrans = timeout_sec;
+ while (*keystring != ',') keystring++;
+ }
+ else if (strncmpic(keystring, US"retry_", 6) == 0)
+ {
+ int retries;
+ if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
+ {
+ *errmsg = US"unsupported dnsdb retry count";
+ rc = DEFER;
+ goto out;
+ }
+ dns_retry = retries;
+ }
+ else
+ break;
+
+ while (isspace(*keystring)) keystring++;
+ if (*keystring++ != ',')
+ {
+ *errmsg = US"dnsdb modifier syntax error";
+ rc = DEFER;
+ goto out;
+ }
+ while (isspace(*keystring)) keystring++;
+ }
+
+/* Figure out the "type" value if it is not T_TXT.
+If the keystring contains an = this must be preceded by a valid type name. */
+
+type = T_TXT;
+if ((equals = Ustrchr(keystring, '=')) != NULL)
+ {
+ int i, len;
+ uschar *tend = equals;
+
+ while (tend > keystring && isspace(tend[-1])) tend--;
+ len = tend - keystring;
+
+ for (i = 0; i < nelem(type_names); i++)
+ if (len == Ustrlen(type_names[i]) &&
+ strncmpic(keystring, US type_names[i], len) == 0)
+ {
+ type = type_values[i];
+ break;
+ }
+
+ if (i >= nelem(type_names))
+ {
+ *errmsg = US"unsupported DNS record type";
+ rc = DEFER;
+ goto out;
+ }
+
+ keystring = equals + 1;
+ while (isspace(*keystring)) keystring++;
+ }
+
+/* Initialize the resolver in case this is the first time it has been used. */
+
+dns_init(FALSE, FALSE, dnssec_mode != OK);
+
+/* The remainder of the string must be a list of domains. As long as the lookup
+for at least one of them succeeds, we return success. Failure means that none
+of them were found.
+
+The original implementation did not support a list of domains. Adding the list
+feature is compatible, except in one case: when PTR records are being looked up
+for a single IPv6 address. Fortunately, we can hack in a compatibility feature
+here: If the type is PTR and no list separator is specified, and the entire
+remaining string is valid as an IP address, set an impossible separator so that
+it is treated as one item. */
+
+if (type == T_PTR && keystring[0] != '<' &&
+ string_is_ip_address(keystring, NULL) != 0)
+ sep = -1;
+
+/* SPF strings should be concatenated without a separator, thus make
+it the default if not defined (see RFC 4408 section 3.1.3).
+Multiple SPF records are forbidden (section 3.1.2) but are currently
+not handled specially, thus they are concatenated with \n by default.
+MX priority and value are space-separated by default.
+SRV and TLSA record parts are space-separated by default. */
+
+if (!outsep2) switch(type)
+ {
+ case T_SPF: outsep2 = US""; break;
+ case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
+ }
+
+/* Now scan the list and do a lookup for each item */
+
+while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
+ {
+ int searchtype = type == T_CSA ? T_SRV : /* record type we want */
+ type == T_MXH ? T_MX :
+ type == T_ZNS ? T_NS : type;
+
+ /* If the type is PTR or CSA, we have to construct the relevant magic lookup
+ key if the original is an IP address (some experimental protocols are using
+ PTR records for different purposes where the key string is a host name, and
+ Exim's extended CSA can be keyed by domains or IP addresses). This code for
+ doing the reversal is now in a separate function. */
+
+ if ((type == T_PTR || type == T_CSA) &&
+ string_is_ip_address(domain, NULL) != 0)
+ domain = dns_build_reverse(domain);
+
+ do
+ {
+ DEBUG(D_lookup) debug_printf_indent("dnsdb key: %s\n", domain);
+
+ /* Do the lookup and sort out the result. There are four special types that
+ are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
+ The first two are handled in a special lookup function so that the facility
+ could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
+ over the types of A lookup. T_MXH affects only what happens later on in
+ this function, but for tidiness it is handled by the "special". If the
+ lookup fails, continue with the next domain. In the case of DEFER, adjust
+ the final "nothing found" result, but carry on to the next domain. */
+
+ found = domain;
+#if HAVE_IPV6
+ if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
+ {
+ if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
+ else if (searchtype == T_AAAA) searchtype = T_A;
+ rc = dns_special_lookup(dnsa, domain, searchtype, CUSS &found);
+ }
+ else
+#endif
+ rc = dns_special_lookup(dnsa, domain, type, CUSS &found);
+
+ lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
+ : dns_is_secure(dnsa) ? US"yes" : US"no";
+
+ if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
+ if ( rc != DNS_SUCCEED
+ || (dnssec_mode == DEFER && !dns_is_secure(dnsa))
+ )
+ {
+ if (defer_mode == DEFER)
+ {
+ dns_retrans = save_retrans;
+ dns_retry = save_retry;
+ dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
+ rc = DEFER; /* always defer */
+ goto out;
+ }
+ if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
+ continue; /* treat defer as fail */
+ }
+
+
+ /* Search the returned records */
+
+ for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
+ rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == searchtype)
+ {
+ if (*do_cache > rr->ttl)
+ *do_cache = rr->ttl;
+
+ if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
+ {
+ for (dns_address * da = dns_address_from_rr(dnsa, rr); da; da = da->next)
+ {
+ if (yield->ptr) yield = string_catn(yield, outsep, 1);
+ yield = string_cat(yield, da->address);
+ }
+ continue;
+ }
+
+ /* Other kinds of record just have one piece of data each, but there may be
+ several of them, of course. */
+
+ if (yield->ptr) yield = string_catn(yield, outsep, 1);
+
+ if (type == T_TXT || type == T_SPF)
+ {
+ if (outsep2 == NULL) /* output only the first item of data */
+ yield = string_catn(yield, US (rr->data+1), (rr->data)[0]);
+ else
+ {
+ /* output all items */
+ int data_offset = 0;
+ while (data_offset < rr->size)
+ {
+ uschar chunk_len = (rr->data)[data_offset++];
+ if (outsep2[0] != '\0' && data_offset != 1)
+ yield = string_catn(yield, outsep2, 1);
+ yield = string_catn(yield, US ((rr->data)+data_offset), chunk_len);
+ data_offset += chunk_len;
+ }
+ }
+ }
+ else if (type == T_TLSA)
+ {
+ uint8_t usage, selector, matching_type;
+ uint16_t payload_length;
+ uschar s[MAX_TLSA_EXPANDED_SIZE];
+ uschar * sp = s;
+ uschar * p = US rr->data;
+
+ usage = *p++;
+ selector = *p++;
+ matching_type = *p++;
+ /* What's left after removing the first 3 bytes above */
+ payload_length = rr->size - 3;
+ sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
+ selector, *outsep2, matching_type, *outsep2);
+ /* Now append the cert/identifier, one hex char at a time */
+ while (payload_length-- > 0 && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4))
+ sp += sprintf(CS sp, "%02x", *p++);
+
+ yield = string_cat(yield, s);
+ }
+ else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
+ {
+ int priority, weight, port;
+ uschar s[264];
+ uschar * p = US rr->data;
+
+ switch (type)
+ {
+ case T_MXH:
+ /* mxh ignores the priority number and includes only the hostnames */
+ GETSHORT(priority, p);
+ break;
+
+ case T_MX:
+ GETSHORT(priority, p);
+ sprintf(CS s, "%d%c", priority, *outsep2);
+ yield = string_cat(yield, s);
+ break;
+
+ case T_SRV:
+ GETSHORT(priority, p);
+ GETSHORT(weight, p);
+ GETSHORT(port, p);
+ sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
+ weight, *outsep2, port, *outsep2);
+ yield = string_cat(yield, s);
+ break;
+
+ case T_CSA:
+ /* See acl_verify_csa() for more comments about CSA. */
+ GETSHORT(priority, p);
+ GETSHORT(weight, p);
+ GETSHORT(port, p);
+
+ if (priority != 1) continue; /* CSA version must be 1 */
+
+ /* If the CSA record we found is not the one we asked for, analyse
+ the subdomain assertions in the port field, else analyse the direct
+ authorization status in the weight field. */
+
+ if (Ustrcmp(found, domain) != 0)
+ {
+ if (port & 1) *s = 'X'; /* explicit authorization required */
+ else *s = '?'; /* no subdomain assertions here */
+ }
+ else
+ {
+ if (weight < 2) *s = 'N'; /* not authorized */
+ else if (weight == 2) *s = 'Y'; /* authorized */
+ else if (weight == 3) *s = '?'; /* unauthorizable */
+ else continue; /* invalid */
+ }
+
+ s[1] = ' ';
+ yield = string_catn(yield, s, 2);
+ break;
+
+ default:
+ break;
+ }
+
+ /* GETSHORT() has advanced the pointer to the target domain. */
+
+ rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
+ (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
+
+ /* If an overlong response was received, the data will have been
+ truncated and dn_expand may fail. */
+
+ if (rc < 0)
+ {
+ log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
+ "domain=%s", dns_text_type(type), domain);
+ break;
+ }
+ else yield = string_cat(yield, s);
+
+ if (type == T_SOA && outsep2 != NULL)
+ {
+ unsigned long serial, refresh, retry, expire, minimum;
+
+ p += rc;
+ yield = string_catn(yield, outsep2, 1);
+
+ rc = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, p,
+ (DN_EXPAND_ARG4_TYPE)s, sizeof(s));
+ if (rc < 0)
+ {
+ log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
+ "domain=%s", dns_text_type(type), domain);
+ break;
+ }
+ else yield = string_cat(yield, s);
+
+ p += rc;
+ GETLONG(serial, p); GETLONG(refresh, p);
+ GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
+ sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
+ *outsep2, serial, *outsep2, refresh,
+ *outsep2, retry, *outsep2, expire, *outsep2, minimum);
+ yield = string_cat(yield, s);
+ }
+ }
+ } /* Loop for list of returned records */
+
+ /* Loop for set of A-lookup types */
+ } while (type == T_ADDRESSES && searchtype != T_A);
+
+ } /* Loop for list of domains */
+
+/* Reclaim unused memory */
+
+gstring_release_unused(yield);
+
+/* If yield NULL we have not found anything. Otherwise, insert the terminating
+zero and return the result. */
+
+dns_retrans = save_retrans;
+dns_retry = save_retry;
+dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
+
+if (!yield || !yield->ptr)
+ rc = failrc;
+else
+ {
+ *result = string_from_gstring(yield);
+ rc = OK;
+ }
+
+out:
+
+store_free_dns_answer(dnsa);
+return rc;
+}
+
+
+
+/*************************************************
+* Version reporting entry point *
+*************************************************/
+
+/* See local README for interface description. */
+
+#include "../version.h"
+
+gstring *
+dnsdb_version_report(gstring * g)
+{
+#ifdef DYNLOOKUP
+g = string_fmt_append(g, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR);
+#endif
+return g;
+}
+
+
+static lookup_info _lookup_info = {
+ .name = US"dnsdb", /* lookup name */
+ .type = lookup_querystyle, /* query style */
+ .open = dnsdb_open, /* open function */
+ .check = NULL, /* check function */
+ .find = dnsdb_find, /* find function */
+ .close = NULL, /* no close function */
+ .tidy = NULL, /* no tidy function */
+ .quote = NULL, /* no quoting function */
+ .version_report = dnsdb_version_report /* version reporting */
+};
+
+#ifdef DYNLOOKUP
+#define dnsdb_lookup_module_info _lookup_module_info
+#endif
+
+static lookup_info *_lookup_list[] = { &_lookup_info };
+lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
+
+/* vi: aw ai sw=2
+*/
+/* End of lookups/dnsdb.c */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 23:16:59 +0000