commit 4b486868473462f9b65cc3ad44c48c2e68ee45ee Author: Tomas Korbar Date: Wed May 17 13:17:30 2023 +0200 Backport SRV record resolution feature diff --git a/mantools/postlink b/mantools/postlink index 46f187e..f738fd3 100755 --- a/mantools/postlink +++ b/mantools/postlink @@ -1128,6 +1128,10 @@ while (<>) { s;\bpostlog_service_name\b;$&;g; s;\bpostlogd_watchdog_timeout\b;$&;g; + s;\buse_srv_lookup\b;$&;g; + s;\ballow_srv_lookup_fallback\b;$&;g; + s;\bignore_srv_lookup_error\b;$&;g; + # Service-defined parameters... s;\bpolicy_time_limit\b;$&;g; diff --git a/proto/postconf.proto b/proto/postconf.proto index 3d53657..29d0aa5 100644 --- a/proto/postconf.proto +++ b/proto/postconf.proto @@ -17698,3 +17698,111 @@ with quotes and backslashes. An attacker should not be able to use such games to circumvent Postfix access policies.

This feature is available in Postfix 3.5 and later.

+ + +%PARAM use_srv_lookup + +

Enables discovery for the specified service(s) using DNS SRV +records. For example, with "use_srv_lookup = submission" and +"relayhost = example.com:submission", the Postfix SMTP client will +look up DNS SRV records for _submission._tcp.example.com, and will +relay email through the hosts and ports that are specified with +those records. See RFC 2782 for details of the host selection +process.

+ +

Specify zero or more service names separated by comma and/or +whitespace. Any name in the services(5) database may be specified, +though in practice only submission, submissions, and smtp make +sense.

+ +

When SRV record lookup is enabled with use_srv_lookup, you can +enclose a domain name in "[]" to force IP address lookup instead +of SRV record lookup.

+ +

Example 1: MUA-to-MTA submission using SRV record lookup for +the "submission" service for domain "example.com". This uses the +default SMTP delivery agent with STARTTLS, and looks up SRV records +for "_submission._tcp.example.com".

+ +
+/etc/postfix/main.cf:
+    use_srv_lookup = submission
+    relayhost = example.com:submission
+    smtp_tls_security_level = may
+    ...see SASL_README for sasl configuration...
+
+ +

Example 2: MUA-to-MTA submission using SRV record lookup for +the "submissions" service for domain "example.org". This uses a +dedicated SMTP delivery agent (smtp-wraptls) with tls_wrappermode +turned on, and looks up SRV records for "_submissions._tcp.example.org". +

+ +

Note: specify the older name "smtps" instead of "submissions" +when a provider has DNS SRV records like "_smtps._tcp.example.org" +instead of "_submissions._tcp.example.org".

+ +
+/etc/postfix/main.cf:
+    use_srv_lookup = submissions
+    default_transport = smtp-wraptls:example.org:submissions
+    ...see SASL_README for sasl configuration...
+
+ +
+/etc/postfix/master.cf:
+    smtp-wraptls   unix   ...   ...   ...   ...   ...   smtp
+        -o { smtp_tls_wrappermode = yes }
+        -o { smtp_tls_security_level = encrypt }
+
+ +

Example 3: Sender-dependent selection for a combination of +MUA-to-MTA submission services. This combines examples 1 and 2 with +examples of how to disable SRV and look up IP address records for +"smtp-relay.example.net" and "smtp-relay.other.example". Again, +specify the older name "smtps" instead of "submissions" when a +provider has DNS SRV records like "_smtps._tcp.example.org" instead +of "_submissions._tcp.example.org".

+ +
+/etc/postfix/main.cf:
+    use_srv_lookup = submission, submissions
+    sender_dependent_default_transport_maps = inline:{
+        # Destinations that support SRV record lookup.
+        { user1@example.com = smtp:example.com:submission }
+        { user2@example.org = smtp-wraptls:example.org:submissions }
+        # Use [destination] to force IP address lookups.
+        { user3@example.net = smtp:[smtp-relay.example.net]:submission }
+        { user4@other.example =
+              smtp-wraptls:[smtp-relay.other.example]:submissions } }
+    ...see SASL_README for sasl configuration...
+
+ +

Example 4: MTA-to-MTA traffic, using SRV record lookup for the +SMTP service. This is useful for Postfix tests, and may be useful +in environments where ports are dynamically assigned to servers. +

+ +
+/etc/postfix/main.cf:
+    use_srv_lookup = smtp
+    # Fall back to MX record lookup when SRV records are unavailable.
+    #allow_srv_lookup_fallback = yes
+    #ignore_srv_lookup_error = yes
+
+ +

This feature was backported from Postfix 3.8.

+ +%PARAM ignore_srv_lookup_error no + +

When SRV record lookup fails, fall back to MX or IP address +lookup as if SRV record lookup was not enabled.

+ +

This feature was backported from Postfix 3.8.

+ +%PARAM allow_srv_lookup_fallback no + +

When SRV record lookup fails or no SRV record exists, fall back +to MX or IP address lookup as if SRV record lookup was not enabled.

+ +

This feature was backported from Postfix 3.8.

diff --git a/src/dns/dns.h b/src/dns/dns.h index b8c4c4a..aac3ca9 100644 --- a/src/dns/dns.h +++ b/src/dns/dns.h @@ -147,10 +147,12 @@ typedef struct DNS_RR { unsigned short class; /* C_IN, etc. */ unsigned int ttl; /* always */ unsigned int dnssec_valid; /* DNSSEC validated */ - unsigned short pref; /* T_MX only */ + unsigned short pref; /* T_MX and T_SRV record related */ + unsigned short weight; /* T_SRV related, defined in rfc2782 */ + unsigned short port; /* T_SRV related, defined in rfc2782 */ struct DNS_RR *next; /* linkage */ size_t data_len; /* actual data size */ - char data[1]; /* actually a bunch of data */ + char *data; /* a bunch of data */ } DNS_RR; /* @@ -172,14 +174,29 @@ extern char *dns_strrecord(VSTRING *, DNS_RR *); /* * dns_rr.c */ +#define DNS_RR_NOPREF (0) +#define DNS_RR_NOWEIGHT (0) +#define DNS_RR_NOPORT (0) + +#define dns_rr_create_noport(qname, rname, type, class, ttl, pref, data, \ + data_len) \ + dns_rr_create((qname), (rname), (type), (class), (ttl), \ + (pref), DNS_RR_NOWEIGHT, DNS_RR_NOPORT, (data), (data_len)) + +#define dns_rr_create_nopref(qname, rname, type, class, ttl, data, data_len) \ + dns_rr_create_noport((qname), (rname), (type), (class), (ttl), \ + DNS_RR_NOPREF, (data), (data_len)) + extern DNS_RR *dns_rr_create(const char *, const char *, ushort, ushort, unsigned, unsigned, + unsigned, unsigned, const char *, size_t); extern void dns_rr_free(DNS_RR *); extern DNS_RR *dns_rr_copy(DNS_RR *); extern DNS_RR *dns_rr_append(DNS_RR *, DNS_RR *); extern DNS_RR *dns_rr_sort(DNS_RR *, int (*) (DNS_RR *, DNS_RR *)); +extern DNS_RR *dns_srv_rr_sort(DNS_RR *); extern int dns_rr_compare_pref_ipv6(DNS_RR *, DNS_RR *); extern int dns_rr_compare_pref_ipv4(DNS_RR *, DNS_RR *); extern int dns_rr_compare_pref_any(DNS_RR *, DNS_RR *); @@ -278,8 +295,9 @@ extern int dns_lookup_rv(const char *, unsigned, DNS_RR **, VSTRING *, * Below is the precedence order. The order between DNS_RETRY and DNS_NOTFOUND * is arbitrary. */ -#define DNS_RECURSE (-7) /* internal only: recursion needed */ -#define DNS_NOTFOUND (-6) /* query ok, data not found */ +#define DNS_RECURSE (-8) /* internal only: recursion needed */ +#define DNS_NOTFOUND (-7) /* query ok, data not found */ +#define DNS_NULLSRV (-6) /* query ok, service unavailable */ #define DNS_NULLMX (-5) /* query ok, service unavailable */ #define DNS_FAIL (-4) /* query failed, don't retry */ #define DNS_INVAL (-3) /* query ok, malformed reply */ diff --git a/src/dns/dns_lookup.c b/src/dns/dns_lookup.c index 11c9281..1aa97a4 100644 --- a/src/dns/dns_lookup.c +++ b/src/dns/dns_lookup.c @@ -688,6 +688,8 @@ static int dns_get_rr(DNS_RR **list, const char *orig_name, DNS_REPLY *reply, int comp_len; ssize_t data_len; unsigned pref = 0; + unsigned weight = 0; + unsigned port = 0; unsigned char *src; unsigned char *dst; int ch; @@ -713,6 +715,18 @@ static int dns_get_rr(DNS_RR **list, const char *orig_name, DNS_REPLY *reply, return (DNS_INVAL); data_len = strlen(temp) + 1; break; + case T_SRV: + GETSHORT(pref, pos); + GETSHORT(weight, pos); + GETSHORT(port, pos); + if (dn_expand(reply->buf, reply->end, pos, temp, sizeof(temp)) < 0) + return (DNS_RETRY); + if (*temp == 0) + return (DNS_NULLSRV); + if (!valid_rr_name(temp, "resource data", fixed->type, reply)) + return (DNS_INVAL); + data_len = strlen(temp) + 1; + break; case T_MX: GETSHORT(pref, pos); if (dn_expand(reply->buf, reply->end, pos, temp, sizeof(temp)) < 0) @@ -808,7 +822,7 @@ static int dns_get_rr(DNS_RR **list, const char *orig_name, DNS_REPLY *reply, break; } *list = dns_rr_create(orig_name, rr_name, fixed->type, fixed->class, - fixed->ttl, pref, tempbuf, data_len); + fixed->ttl, pref, weight, port, tempbuf, data_len); return (DNS_OK); } @@ -906,7 +920,7 @@ static int dns_get_answer(const char *orig_name, DNS_REPLY *reply, int type, resource_found++; rr->dnssec_valid = *maybe_secure ? reply->dnssec_ad : 0; *rrlist = dns_rr_append(*rrlist, rr); - } else if (status == DNS_NULLMX) { + } else if (status == DNS_NULLMX || status == DNS_NULLSRV) { CORRUPT(status); /* TODO: use better name */ } else if (not_found_status != DNS_RETRY) not_found_status = status; @@ -1032,6 +1046,12 @@ int dns_lookup_x(const char *name, unsigned type, unsigned flags, name); SET_H_ERRNO(NO_DATA); return (status); + case DNS_NULLSRV: + if (why) + vstring_sprintf(why, "Domain %s does not support SRV requests", + name); + SET_H_ERRNO(NO_DATA); + return (status); case DNS_OK: if (rrlist && dns_rr_filter_maps) { if (dns_rr_filter_execute(rrlist) < 0) { diff --git a/src/dns/dns_rr.c b/src/dns/dns_rr.c index b550788..15b5dee 100644 --- a/src/dns/dns_rr.c +++ b/src/dns/dns_rr.c @@ -7,13 +7,15 @@ /* #include /* /* DNS_RR *dns_rr_create(qname, rname, type, class, ttl, preference, -/* data, data_len) +/* weight, port, data, data_len) /* const char *qname; /* const char *rname; /* unsigned short type; /* unsigned short class; /* unsigned int ttl; /* unsigned preference; +/* unsigned weight; +/* unsigned port; /* const char *data; /* size_t data_len; /* @@ -49,6 +51,30 @@ /* DNS_RR *dns_rr_remove(list, record) /* DNS_RR *list; /* DNS_RR *record; +/* +/* DNS_RR *dns_srv_rr_sort(list) +/* DNS_RR *list; +/* AUXILIARY FUNCTIONS +/* DNS_RR *dns_rr_create_nopref(qname, rname, type, class, ttl, +/* data, data_len) +/* const char *qname; +/* const char *rname; +/* unsigned short type; +/* unsigned short class; +/* unsigned int ttl; +/* const char *data; +/* size_t data_len; +/* +/* DNS_RR *dns_rr_create_noport(qname, rname, type, class, ttl, +/* preference, data, data_len) +/* const char *qname; +/* const char *rname; +/* unsigned short type; +/* unsigned short class; +/* unsigned int ttl; +/* unsigned preference; +/* const char *data; +/* size_t data_len; /* DESCRIPTION /* The routines in this module maintain memory for DNS resource record /* information, and maintain lists of DNS resource records. @@ -56,10 +82,14 @@ /* dns_rr_create() creates and initializes one resource record. /* The \fIqname\fR field specifies the query name. /* The \fIrname\fR field specifies the reply name. -/* \fIpreference\fR is used for MX records; \fIdata\fR is a null +/* \fIpreference\fR is used for MX and SRV records; \fIweight\fR +/* and \fIport\fR are used for SRV records; \fIdata\fR is a null /* pointer or specifies optional resource-specific data; /* \fIdata_len\fR is the amount of resource-specific data. /* +/* dns_rr_create_nopref() and dns_rr_create_noport() are convenience +/* wrappers around dns_rr_create() that take fewer arguments. +/* /* dns_rr_free() releases the resource used by of zero or more /* resource records. /* @@ -81,6 +111,9 @@ /* dns_rr_remove() removes the specified record from the specified list. /* The updated list is the result value. /* The record MUST be a list member. +/* +/* dns_srv_rr_sort() sorts a list of SRV records according to +/* their priority and weight as described in RFC 2782. /* LICENSE /* .ad /* .fi @@ -113,11 +146,15 @@ DNS_RR *dns_rr_create(const char *qname, const char *rname, ushort type, ushort class, unsigned int ttl, unsigned pref, + unsigned weight, unsigned port, const char *data, size_t data_len) { DNS_RR *rr; - rr = (DNS_RR *) mymalloc(sizeof(*rr) + data_len - 1); + /* + * Note: if this function is changed, update dns_rr_copy(). + */ + rr = (DNS_RR *) mymalloc(sizeof(*rr)); rr->qname = mystrdup(qname); rr->rname = mystrdup(rname); rr->type = type; @@ -125,8 +162,14 @@ DNS_RR *dns_rr_create(const char *qname, const char *rname, rr->ttl = ttl; rr->dnssec_valid = 0; rr->pref = pref; - if (data && data_len > 0) + rr->weight = weight; + rr->port = port; + if (data_len != 0) { + rr->data = mymalloc(data_len); memcpy(rr->data, data, data_len); + } else { + rr->data = 0; + } rr->data_len = data_len; rr->next = 0; return (rr); @@ -141,6 +184,8 @@ void dns_rr_free(DNS_RR *rr) dns_rr_free(rr->next); myfree(rr->qname); myfree(rr->rname); + if (rr->data) + myfree(rr->data); myfree((void *) rr); } } @@ -149,16 +194,17 @@ void dns_rr_free(DNS_RR *rr) DNS_RR *dns_rr_copy(DNS_RR *src) { - ssize_t len = sizeof(*src) + src->data_len - 1; DNS_RR *dst; /* - * Combine struct assignment and data copy in one block copy operation. + * Note: struct copy, because dns_rr_create() would not copy all fields. */ - dst = (DNS_RR *) mymalloc(len); - memcpy((void *) dst, (void *) src, len); + dst = (DNS_RR *) mymalloc(sizeof(*dst)); + *dst = *src; dst->qname = mystrdup(src->qname); dst->rname = mystrdup(src->rname); + if (dst->data) + dst->data = mymemdup(src->data, src->data_len); dst->next = 0; return (dst); } @@ -247,6 +293,12 @@ DNS_RR *dns_rr_sort(DNS_RR *list, int (*compar) (DNS_RR *, DNS_RR *)) int len; int i; + /* + * Avoid mymalloc() panic. + */ + if (list == 0) + return (list); + /* * Save state and initialize. */ @@ -293,6 +345,12 @@ DNS_RR *dns_rr_shuffle(DNS_RR *list) int i; int r; + /* + * Avoid mymalloc() panic. + */ + if (list == 0) + return (list); + /* * Build linear array with pointers to each list element. */ @@ -345,3 +403,141 @@ DNS_RR *dns_rr_remove(DNS_RR *list, DNS_RR *record) } return (list); } + +/* weight_order - sort equal-priority records by weight */ + +static void weight_order(DNS_RR **array, int count) +{ + int unordered_weights; + int i; + + /* + * Compute the sum of record weights. If weights are not supplied then + * this function would be a noop. In fact this would be a noop when all + * weights have the same value, whether that weight is zero or not. There + * is no need to give special treatment to zero weights. + */ + for (unordered_weights = 0, i = 0; i < count; i++) + unordered_weights += array[i]->weight; + if (unordered_weights == 0) + return; + + /* + * The record ordering code below differs from RFC 2782 when the input + * contains a mix of zero and non-zero weights: the code below does not + * give special treatment to zero weights. Instead, it treats a zero + * weight just like any other small weight. Fewer special cases make for + * code that is simpler and more robust. + */ + for (i = 0; i < count - 1; i++) { + int running_sum; + int threshold; + int k; + DNS_RR *temp; + + /* + * Choose a random threshold [0..unordered_weights] inclusive. + */ + threshold = myrand() % (unordered_weights + 1); + + /* + * Move the first record with running_sum >= threshold to the ordered + * list, and update unordered_weights. + */ + for (running_sum = 0, k = i; k < count; k++) { + running_sum += array[k]->weight; + if (running_sum >= threshold) { + unordered_weights -= array[k]->weight; + temp = array[i]; + array[i] = array[k]; + array[k] = temp; + break; + } + } + } +} + +/* dns_srv_rr_sort - sort resource record list */ + +DNS_RR *dns_srv_rr_sort(DNS_RR *list) +{ + int (*saved_user) (DNS_RR *, DNS_RR *); + DNS_RR **rr_array; + DNS_RR *rr; + int len; + int i; + int r; + int cur_pref; + int left_bound; /* inclusive */ + int right_bound; /* non-inclusive */ + + /* + * Avoid mymalloc() panic, or rr_array[0] fence-post error. + */ + if (list == 0) + return (list); + + /* + * Save state and initialize. + */ + saved_user = dns_rr_sort_user; + dns_rr_sort_user = dns_rr_compare_pref_any; + + /* + * Build linear array with pointers to each list element. + */ + for (len = 0, rr = list; rr != 0; len++, rr = rr->next) + /* void */ ; + rr_array = (DNS_RR **) mymalloc(len * sizeof(*rr_array)); + for (len = 0, rr = list; rr != 0; len++, rr = rr->next) + rr_array[len] = rr; + + /* + * Shuffle resource records. Every element has an equal chance of landing + * in slot 0. After that every remaining element has an equal chance of + * landing in slot 1, ... This is exactly n! states for n! permutations. + */ + for (i = 0; i < len - 1; i++) { + r = i + (myrand() % (len - i)); /* Victor&Son */ + rr = rr_array[i]; + rr_array[i] = rr_array[r]; + rr_array[r] = rr; + } + + /* First order the records by preference. */ + qsort((void *) rr_array, len, sizeof(*rr_array), dns_rr_sort_callback); + + /* + * Walk through records and sort the records in every same-preference + * partition according to their weight. Note that left_bound is + * inclusive, and that right-bound is non-inclusive. + */ + left_bound = 0; + cur_pref = rr_array[left_bound]->pref; /* assumes len > 0 */ + + for (right_bound = 1; /* see below */ ; right_bound++) { + if (right_bound == len || rr_array[right_bound]->pref != cur_pref) { + if (right_bound - left_bound > 1) + weight_order(rr_array + left_bound, right_bound - left_bound); + if (right_bound == len) + break; + left_bound = right_bound; + cur_pref = rr_array[left_bound]->pref; + } + } + + /* + * Fix the links. + */ + for (i = 0; i < len - 1; i++) + rr_array[i]->next = rr_array[i + 1]; + rr_array[i]->next = 0; + list = rr_array[0]; + + /* + * Cleanup. + */ + myfree((void *) rr_array); + dns_rr_sort_user = saved_user; + return (list); +} diff --git a/src/dns/dns_sa_to_rr.c b/src/dns/dns_sa_to_rr.c index 6b9efcc..b5dee20 100644 --- a/src/dns/dns_sa_to_rr.c +++ b/src/dns/dns_sa_to_rr.c @@ -55,14 +55,14 @@ DNS_RR *dns_sa_to_rr(const char *hostname, unsigned pref, struct sockaddr *sa) #define DUMMY_TTL 0 if (sa->sa_family == AF_INET) { - return (dns_rr_create(hostname, hostname, T_A, C_IN, DUMMY_TTL, pref, - (char *) &SOCK_ADDR_IN_ADDR(sa), - sizeof(SOCK_ADDR_IN_ADDR(sa)))); + return (dns_rr_create_noport(hostname, hostname, T_A, C_IN, DUMMY_TTL, + pref, (char *) &SOCK_ADDR_IN_ADDR(sa), + sizeof(SOCK_ADDR_IN_ADDR(sa)))); #ifdef HAS_IPV6 } else if (sa->sa_family == AF_INET6) { - return (dns_rr_create(hostname, hostname, T_AAAA, C_IN, DUMMY_TTL, pref, - (char *) &SOCK_ADDR_IN6_ADDR(sa), - sizeof(SOCK_ADDR_IN6_ADDR(sa)))); + return (dns_rr_create_noport(hostname, hostname, T_AAAA, C_IN, DUMMY_TTL, + pref, (char *) &SOCK_ADDR_IN6_ADDR(sa), + sizeof(SOCK_ADDR_IN6_ADDR(sa)))); #endif } else { errno = EAFNOSUPPORT; @@ -121,7 +121,7 @@ int main(int argc, char **argv) resv[len++] = res; qsort((void *) resv, len, sizeof(*resv), compare_family); for (n = 0; n < len; n++) { - if ((rr = dns_sa_to_rr(argv[0], 0, resv[n]->ai_addr)) == 0) + if ((rr = dns_sa_to_rr(argv[0], DNS_RR_NOPREF, resv[n]->ai_addr)) == 0) msg_fatal("dns_sa_to_rr: %m"); if (dns_rr_to_pa(rr, &hostaddr) == 0) msg_fatal("dns_rr_to_pa: %m"); diff --git a/src/dns/dns_strrecord.c b/src/dns/dns_strrecord.c index 6b8e989..1e3b743 100644 --- a/src/dns/dns_strrecord.c +++ b/src/dns/dns_strrecord.c @@ -80,6 +80,10 @@ char *dns_strrecord(VSTRING *buf, DNS_RR *rr) case T_MX: vstring_sprintf_append(buf, "%u %s.", rr->pref, rr->data); break; + case T_SRV: + vstring_sprintf_append(buf, "%u %u %u %s.", rr->pref, rr->weight, + rr->port, rr->data); + break; case T_TLSA: if (rr->data_len >= 3) { uint8_t *ip = (uint8_t *) rr->data; diff --git a/src/dns/dns_strtype.c b/src/dns/dns_strtype.c index 70e59ac..7eebe3c 100644 --- a/src/dns/dns_strtype.c +++ b/src/dns/dns_strtype.c @@ -180,6 +180,9 @@ static struct dns_type_map dns_type_map[] = { #ifdef T_ANY T_ANY, "ANY", #endif +#ifdef T_SRV + T_SRV, "SRV", +#endif }; /* dns_strtype - translate DNS query type to string */ diff --git a/src/global/mail_params.h b/src/global/mail_params.h index 74459d9..f8bb550 100644 --- a/src/global/mail_params.h +++ b/src/global/mail_params.h @@ -4206,6 +4206,21 @@ extern char *var_info_log_addr_form; #define DEF_RHEL_IPV6_NORMALIZE 0 extern bool var_rhel_ipv6_normalize; + /* + * SRV lookup support. + */ +#define VAR_USE_SRV_LOOKUP "use_srv_lookup" +#define DEF_USE_SRV_LOOKUP "" +extern char *var_use_srv_lookup; + +#define VAR_IGN_SRV_LOOKUP_ERR "ignore_srv_lookup_error" +#define DEF_IGN_SRV_LOOKUP_ERR 0 +extern bool var_ign_srv_lookup_err; + +#define VAR_ALLOW_SRV_FALLBACK "allow_srv_lookup_fallback" +#define DEF_ALLOW_SRV_FALLBACK 0 +extern bool var_allow_srv_fallback; + /* LICENSE /* .ad /* .fi diff --git a/src/posttls-finger/posttls-finger.c b/src/posttls-finger/posttls-finger.c index a3a9946..b428cb3 100644 --- a/src/posttls-finger/posttls-finger.c +++ b/src/posttls-finger/posttls-finger.c @@ -236,6 +236,8 @@ /* is encountered, up to 5 times or as specified with the \fB-m\fR option. /* By default reconnection is disabled, specify a positive delay to /* enable this behavior. +/* .IP "\fB-R\fR" +/* Use SRV lookup instead of MX. /* .IP "\fB-s \fIservername\fR" /* The server name to send with the TLS Server Name Indication (SNI) /* extension. When the server has DANE TLSA records, this parameter @@ -466,6 +468,7 @@ typedef struct STATE { DNS_RR *mx; /* MX RRset qname, rname, valid */ int pass; /* Pass number, 2 for reconnect */ int nochat; /* disable chat logging */ + int dosrv; /* look up SRV records instead of MX */ char *helo; /* Server name from EHLO reply */ DSN_BUF *why; /* SMTP-style error message */ VSTRING *buffer; /* Response buffer */ @@ -1150,7 +1153,7 @@ static VSTREAM *connect_addr(STATE *state, DNS_RR *addr) /* addr_one - address lookup for one host name */ static DNS_RR *addr_one(STATE *state, DNS_RR *addr_list, const char *host, - int res_opt, unsigned pref) + int res_opt, unsigned pref, unsigned port) { static const char *myname = "addr_one"; DSN_BUF *why = state->why; @@ -1173,6 +1176,8 @@ static DNS_RR *addr_one(STATE *state, DNS_RR *addr_list, const char *host, if ((addr = dns_sa_to_rr(host, pref, res0->ai_addr)) == 0) msg_fatal("host %s: conversion error for address family %d: %m", host, ((struct sockaddr *) (res0->ai_addr))->sa_family); + addr->pref = pref; + addr->port = port; addr_list = dns_rr_append(addr_list, addr); freeaddrinfo(res0); return (addr_list); @@ -1189,8 +1194,10 @@ static DNS_RR *addr_one(STATE *state, DNS_RR *addr_list, const char *host, why->reason, DNS_REQ_FLAG_NONE, proto_info->dns_atype_list)) { case DNS_OK: - for (rr = addr; rr; rr = rr->next) + for (rr = addr; rr; rr = rr->next) { rr->pref = pref; + rr->port = port; + } addr_list = dns_rr_append(addr_list, addr); return (addr_list); default: @@ -1277,15 +1284,15 @@ static DNS_RR *mx_addr_list(STATE *state, DNS_RR *mx_names) #endif for (rr = mx_names; rr; rr = rr->next) { - if (rr->type != T_MX) + if (rr->type != T_MX && rr->type != T_SRV) msg_panic("%s: bad resource type: %d", myname, rr->type); addr_list = addr_one(state, addr_list, (char *) rr->data, res_opt, - rr->pref); + rr->pref, rr->port); } return (addr_list); } -/* smtp_domain_addr - mail exchanger address lookup */ +/* domain_addr - mail exchanger address lookup */ static DNS_RR *domain_addr(STATE *state, char *domain) { @@ -1350,6 +1357,74 @@ static DNS_RR *domain_addr(STATE *state, char *domain) return (addr_list); } +/* service_addr - mail exchanger address lookup */ + +static DNS_RR *service_addr(STATE *state, const char *domain, + const char *service) +{ + VSTRING *srv_qname = vstring_alloc(100); + char *str_srv_qname; + DNS_RR *srv_names; + DNS_RR *addr_list = 0; + int r = 0; /* Resolver flags */ + const char *aname; + + dsb_reset(state->why); + +#if (RES_USE_DNSSEC != 0) && (RES_USE_EDNS0 != 0) + r |= RES_USE_DNSSEC; +#endif + + vstring_sprintf(srv_qname, "_%s._tcp.%s", service, domain); + str_srv_qname = STR(srv_qname); + + /* + * IDNA support. + */ +#ifndef NO_EAI + if (!allascii(str_srv_qname) + && (aname = midna_domain_to_ascii(str_srv_qname)) != 0) { + msg_info("%s asciified to %s", str_srv_qname, aname); + } else +#endif + aname = str_srv_qname; + + switch (dns_lookup(aname, T_SRV, r, &srv_names, (VSTRING *) 0, + state->why->reason)) { + default: + dsb_status(state->why, "4.4.3"); + break; + case DNS_INVAL: + dsb_status(state->why, "5.4.4"); + break; + case DNS_NULLMX: + dsb_status(state->why, "5.1.0"); + break; + case DNS_FAIL: + dsb_status(state->why, "5.4.3"); + break; + case DNS_OK: + /* Shuffle then sort the SRV rr records by priority and weight. */ + srv_names = dns_srv_rr_sort(srv_names); + addr_list = mx_addr_list(state, srv_names); + state->mx = dns_rr_copy(srv_names); + dns_rr_free(srv_names); + if (addr_list == 0) { + msg_warn("no SRV host for %s has a valid address record", + str_srv_qname); + break; + } + /* TODO: sort by priority, weight, and address family preference. */ + break; + case DNS_NOTFOUND: + dsb_status(state->why, "5.4.4"); + break; + } + + vstring_free(srv_qname); + return (addr_list); +} + /* host_addr - direct host lookup */ static DNS_RR *host_addr(STATE *state, const char *host) @@ -1376,7 +1451,8 @@ static DNS_RR *host_addr(STATE *state, const char *host) ahost = host; #define PREF0 0 - addr_list = addr_one(state, (DNS_RR *) 0, ahost, res_opt, PREF0); +#define NOPORT 0 + addr_list = addr_one(state, (DNS_RR *) 0, ahost, res_opt, PREF0, NOPORT); if (addr_list && addr_list->next) { addr_list = dns_rr_shuffle(addr_list); if (inet_proto_info()->ai_family_list[1] != 0) @@ -1465,7 +1541,8 @@ static int dane_host_level(STATE *state, DNS_RR *addr) /* parse_destination - parse host/port destination */ static char *parse_destination(char *destination, char *def_service, - char **hostp, unsigned *portp) + char **hostp, char **servicep, + unsigned *portp) { char *buf = mystrdup(destination); char *service; @@ -1481,12 +1558,13 @@ static char *parse_destination(char *destination, char *def_service, * Parse the host/port information. We're working with a copy of the * destination argument so the parsing can be destructive. */ - if ((err = host_port(buf, hostp, (char *) 0, &service, def_service)) != 0) + if ((err = host_port(buf, hostp, (char *) 0, servicep, def_service)) != 0) msg_fatal("%s in server description: %s", err, destination); /* * Convert service to port number, network byte order. */ + service = *servicep; if (alldig(service)) { if ((port = atoi(service)) >= 65536 || port == 0) msg_fatal("bad network port in destination: %s", destination); @@ -1507,17 +1585,21 @@ static char *parse_destination(char *destination, char *def_service, static void connect_remote(STATE *state, char *dest) { DNS_RR *addr; - char *buf; - char *domain; /* When reconnecting use IP address of previous session */ if (state->addr == 0) { + char *buf; + char *domain; + char *service; + buf = parse_destination(dest, state->smtp ? "smtp" : "24", - &domain, &state->port); + &domain, &service, &state->port); if (!state->nexthop) state->nexthop = mystrdup(domain); if (state->smtp == 0 || *dest == '[') state->addr = host_addr(state, domain); + else if (state->dosrv) + state->addr = service_addr(state, domain, service); else state->addr = domain_addr(state, domain); myfree(buf); @@ -1531,10 +1613,14 @@ static void connect_remote(STATE *state, char *dest) for (addr = state->addr; addr; addr = addr->next) { int level = dane_host_level(state, addr); + if (addr->port) /* SRV port override */ + state->port = htons(addr->port); + if (level == TLS_LEV_INVALID || (state->stream = connect_addr(state, addr)) == 0) { - msg_info("Failed to establish session to %s via %s: %s", - dest, HNAME(addr), vstring_str(state->why->reason)); + msg_info("Failed to establish session to %s via %s:%u: %s", + dest, HNAME(addr), addr->port, + vstring_str(state->why->reason)); continue; } /* We have a connection */ @@ -1819,6 +1905,7 @@ static void parse_options(STATE *state, int argc, char *argv[]) state->smtp = 1; state->pass = 1; + state->dosrv = 0; state->reconnect = -1; state->max_reconnect = 5; state->wrapper_mode = 0; @@ -1829,7 +1916,7 @@ static void parse_options(STATE *state, int argc, char *argv[]) memset((void *) &state->options, 0, sizeof(state->options)); state->options.host_lookup = mystrdup("dns"); -#define OPTS "a:ch:o:St:T:v" +#define OPTS "a:ch:o:RSt:T:v" #ifdef USE_TLS #define TLSOPTS "A:Cd:fF:g:H:k:K:l:L:m:M:p:P:r:s:wX" @@ -1868,6 +1955,9 @@ static void parse_options(STATE *state, int argc, char *argv[]) case 'o': override(optarg); break; + case 'R': + state->dosrv = 1; + break; case 'S': state->smtp = 0; break; diff --git a/src/smtp/lmtp_params.c b/src/smtp/lmtp_params.c index 973cb5d..ff074cd 100644 --- a/src/smtp/lmtp_params.c +++ b/src/smtp/lmtp_params.c @@ -64,6 +64,7 @@ VAR_LMTP_DSN_FILTER, DEF_LMTP_DSN_FILTER, &var_smtp_dsn_filter, 0, 0, VAR_LMTP_DNS_RE_FILTER, DEF_LMTP_DNS_RE_FILTER, &var_smtp_dns_re_filter, 0, 0, VAR_TLSPROXY_SERVICE, DEF_TLSPROXY_SERVICE, &var_tlsproxy_service, 1, 0, + VAR_USE_SRV_LOOKUP, DEF_USE_SRV_LOOKUP, &var_use_srv_lookup, 0, 0, 0, }; static const CONFIG_TIME_TABLE lmtp_time_table[] = { @@ -126,5 +127,7 @@ VAR_LMTP_REC_DEADLINE, DEF_LMTP_REC_DEADLINE, &var_smtp_rec_deadline, VAR_LMTP_DUMMY_MAIL_AUTH, DEF_LMTP_DUMMY_MAIL_AUTH, &var_smtp_dummy_mail_auth, VAR_LMTP_BALANCE_INET_PROTO, DEF_LMTP_BALANCE_INET_PROTO, &var_smtp_balance_inet_proto, + VAR_IGN_SRV_LOOKUP_ERR, DEF_IGN_SRV_LOOKUP_ERR, &var_ign_srv_lookup_err, + VAR_ALLOW_SRV_FALLBACK, DEF_ALLOW_SRV_FALLBACK, &var_allow_srv_fallback, 0, }; diff --git a/src/smtp/smtp.c b/src/smtp/smtp.c index 6ca2d5c..f402876 100644 --- a/src/smtp/smtp.c +++ b/src/smtp/smtp.c @@ -146,6 +146,7 @@ /* RFC 2046 (MIME: Media Types) /* RFC 2554 (AUTH command) /* RFC 2821 (SMTP protocol) +/* RFC 2782 (SRV resource records) /* RFC 2920 (SMTP Pipelining) /* RFC 3207 (STARTTLS command) /* RFC 3461 (SMTP DSN Extension) @@ -330,6 +331,17 @@ /* .IP "\fBinfo_log_address_format (external)\fR" /* The email address form that will be used in non-debug logging /* (info, warning, etc.). +/* .PP +/* Backported from Postfix version 3.8: +/* .IP "\fBuse_srv_lookup (empty)\fR" +/* Enables discovery for the specified service(s) using DNS SRV +/* records. +/* .IP "\fBignore_srv_lookup_error (no)\fR" +/* When SRV record lookup fails, fall back to MX or IP address +/* lookup as if SRV record lookup was not enabled. +/* .IP "\fBallow_srv_lookup_fallback (no)\fR" +/* When SRV record lookup fails or no SRV record exists, fall back +/* to MX or IP address lookup as if SRV record lookup was not enabled. /* MIME PROCESSING CONTROLS /* .ad /* .fi @@ -1046,6 +1058,9 @@ bool var_smtp_dummy_mail_auth; char *var_smtp_dsn_filter; char *var_smtp_dns_re_filter; bool var_smtp_balance_inet_proto; +char *var_use_srv_lookup; +bool var_ign_srv_lookup_err; +bool var_allow_srv_fallback; /* Special handling of 535 AUTH errors. */ char *var_smtp_sasl_auth_cache_name; @@ -1068,6 +1083,7 @@ MAPS *smtp_pix_bug_maps; HBC_CHECKS *smtp_header_checks; /* limited header checks */ HBC_CHECKS *smtp_body_checks; /* limited body checks */ SMTP_CLI_ATTR smtp_cli_attr; /* parsed command-line */ +STRING_LIST *smtp_use_srv_lookup; #ifdef USE_TLS @@ -1351,6 +1367,14 @@ static void post_init(char *unused_name, char **argv) * the process lifetime. */ get_cli_attr(&smtp_cli_attr, argv); + + /* + * Service discovery with SRV record lookup. + */ + if (*var_use_srv_lookup) + smtp_use_srv_lookup = string_list_init(VAR_USE_SRV_LOOKUP, + MATCH_FLAG_RETURN, + var_use_srv_lookup); } /* pre_init - pre-jail initialization */ diff --git a/src/smtp/smtp.h b/src/smtp/smtp.h index 281cfe4..3f4c209 100644 --- a/src/smtp/smtp.h +++ b/src/smtp/smtp.h @@ -84,6 +84,14 @@ typedef struct SMTP_ITERATOR { vstring_strcpy((iter)->dest, STR((iter)->saved_dest)); \ } while (0) +#define SMTP_ITER_UPDATE_HOST(iter, _host, _addr, _rr) do { \ + vstring_strcpy((iter)->host, (_host)); \ + vstring_strcpy((iter)->addr, (_addr)); \ + (iter)->rr = (_rr); \ + if ((_rr)->port) \ + (iter)->port = htons((_rr)->port); /* SRV port override */ \ + } while (0) + /* * TLS Policy support. */ @@ -261,6 +269,7 @@ typedef struct SMTP_STATE { #define SMTP_MISC_FLAG_COMPLETE_SESSION (1<<7) #define SMTP_MISC_FLAG_PREF_IPV6 (1<<8) #define SMTP_MISC_FLAG_PREF_IPV4 (1<<9) +#define SMTP_MISC_FLAG_FALLBACK_SRV_TO_MX (1<<10) #define SMTP_MISC_FLAG_CONN_CACHE_MASK \ (SMTP_MISC_FLAG_CONN_LOAD | SMTP_MISC_FLAG_CONN_STORE) @@ -300,6 +309,8 @@ extern MAPS *smtp_generic_maps; /* make internal address valid */ extern int smtp_ext_prop_mask; /* address externsion propagation */ extern unsigned smtp_dns_res_opt; /* DNS query flags */ +extern STRING_LIST *smtp_use_srv_lookup;/* services with SRV record lookup */ + #ifdef USE_TLS extern TLS_APPL_STATE *smtp_tls_ctx; /* client-side TLS engine */ diff --git a/src/smtp/smtp_addr.c b/src/smtp/smtp_addr.c index 2210ff7..7f20838 100644 --- a/src/smtp/smtp_addr.c +++ b/src/smtp/smtp_addr.c @@ -17,6 +17,15 @@ /* char *name; /* int misc_flags; /* DSN_BUF *why; +/* +/* DNS_RR *smtp_service_addr(name, service, mxrr, misc_flags, why, +/* found_myself) +/* const char *name; +/* const char *service; +/* DNS_RR **mxrr; +/* int misc_flags; +/* DSN_BUF *why; +/* int *found_myself; /* DESCRIPTION /* This module implements Internet address lookups. By default, /* lookups are done via the Internet domain name service (DNS). @@ -33,6 +42,8 @@ /* destination. If MX records were found, the rname, qname, /* and dnssec validation status of the MX RRset are returned /* via mxrr, which the caller must free with dns_rr_free(). +/* Fallback from MX to address lookups is governed by RFC 2821, +/* and by local policy (var_ign_mx_lookup_err). /* /* When no mail exchanger is listed in the DNS for \fIname\fR, the /* request is passed to smtp_host_addr(). @@ -44,8 +55,18 @@ /* host. The host can be specified as a numerical Internet network /* address, or as a symbolic host name. /* -/* Results from smtp_domain_addr() or smtp_host_addr() are -/* destroyed by dns_rr_free(), including null lists. +/* smtp_service_addr() looks up addresses for hosts specified +/* in SRV records for the specified domain and service. This +/* supports the features of smtp_domain_addr() except that +/* the order of SRV records is determined by RFC 2782, and +/* that address records are not sorted by IP address family +/* preference. Fallback from SRV to MX or address lookups is +/* governed by local policy (var_ign_mx_lookup_err and +/* var_allow_srv_fallback). +/* +/* Results from smtp_domain_addr(), smtp_host_addr(), and +/* smtp_service_addr() are destroyed by dns_rr_free(), including +/* null lists. /* DIAGNOSTICS /* Panics: interface violations. For example, calling smtp_domain_addr() /* when DNS lookups are explicitly disabled. @@ -130,7 +151,8 @@ static void smtp_print_addr(const char *what, DNS_RR *addr_list) /* smtp_addr_one - address lookup for one host name */ static DNS_RR *smtp_addr_one(DNS_RR *addr_list, const char *host, int res_opt, - unsigned pref, DSN_BUF *why) + unsigned pref, unsigned port, + DSN_BUF *why) { const char *myname = "smtp_addr_one"; DNS_RR *addr = 0; @@ -153,6 +175,8 @@ static DNS_RR *smtp_addr_one(DNS_RR *addr_list, const char *host, int res_opt, if ((addr = dns_sa_to_rr(host, pref, res0->ai_addr)) == 0) msg_fatal("host %s: conversion error for address family " "%d: %m", host, res0->ai_addr->sa_family); + addr->pref = pref; + addr->port = port; addr_list = dns_rr_append(addr_list, addr); freeaddrinfo(res0); return (addr_list); @@ -172,8 +196,10 @@ static DNS_RR *smtp_addr_one(DNS_RR *addr_list, const char *host, int res_opt, why->reason, DNS_REQ_FLAG_NONE, proto_info->dns_atype_list)) { case DNS_OK: - for (rr = addr; rr; rr = rr->next) + for (rr = addr; rr; rr = rr->next) { rr->pref = pref; + rr->port = port; + } addr_list = dns_rr_append(addr_list, addr); return (addr_list); default: @@ -283,10 +309,10 @@ static DNS_RR *smtp_addr_list(DNS_RR *mx_names, DSN_BUF *why) * tweaking the in-process resolver flags. */ for (rr = mx_names; rr; rr = rr->next) { - if (rr->type != T_MX) + if (rr->type != T_MX && rr->type != T_SRV) msg_panic("smtp_addr_list: bad resource type: %d", rr->type); addr_list = smtp_addr_one(addr_list, (char *) rr->data, res_opt, - rr->pref, why); + rr->pref, rr->port, why); } return (addr_list); } @@ -669,7 +695,7 @@ DNS_RR *smtp_host_addr(const char *host, int misc_flags, DSN_BUF *why) * address to internal form. Otherwise, the host is specified by name. */ #define PREF0 0 - addr_list = smtp_addr_one((DNS_RR *) 0, ahost, res_opt, PREF0, why); + addr_list = smtp_addr_one((DNS_RR *) 0, ahost, res_opt, PREF0, 0, why); if (addr_list && (misc_flags & SMTP_MISC_FLAG_LOOP_DETECT) && smtp_find_self(addr_list) != 0) { @@ -691,3 +717,135 @@ DNS_RR *smtp_host_addr(const char *host, int misc_flags, DSN_BUF *why) smtp_print_addr(host, addr_list); return (addr_list); } + +/* smtp_service_addr - service address lookup */ + +DNS_RR *smtp_service_addr(const char *name, const char *service, DNS_RR **mxrr, + int misc_flags, DSN_BUF *why, + int *found_myself) +{ + static VSTRING *srv_qname = 0; + const char *str_srv_qname; + DNS_RR *srv_names = 0; + DNS_RR *addr_list = 0; + DNS_RR *self = 0; + unsigned best_pref; + unsigned best_found; + int r = 0; + const char *aname; + int allow_non_srv_fallback = var_allow_srv_fallback; + + dsb_reset(why); + + /* + * Sanity check. + */ + if (smtp_dns_support == SMTP_DNS_DISABLED) + msg_panic("smtp_service_addr: DNS lookup is disabled"); + + if (smtp_dns_support == SMTP_DNS_DNSSEC) { + r |= RES_USE_DNSSEC; + } + if (srv_qname == 0) + srv_qname = vstring_alloc(100); + vstring_sprintf(srv_qname, "_%s._tcp.%s", service, name); + str_srv_qname = STR(srv_qname); + + /* + * IDNA support. + */ +#ifndef NO_EAI + if (!allascii(str_srv_qname) + && (aname = midna_domain_to_ascii(str_srv_qname)) != 0) { + if (msg_verbose) + msg_info("%s asciified to %s", str_srv_qname, aname); + } else +#endif + aname = str_srv_qname; + + switch (dns_lookup(aname, T_SRV, r, &srv_names, (VSTRING *) 0, + why->reason)) { + default: + dsb_status(why, "4.4.3"); + allow_non_srv_fallback |= var_ign_srv_lookup_err; + break; + case DNS_INVAL: + dsb_status(why, "5.4.4"); + allow_non_srv_fallback |= var_ign_srv_lookup_err; + break; + case DNS_POLICY: + dsb_status(why, "4.7.0"); + break; + case DNS_FAIL: + dsb_status(why, "5.4.3"); + allow_non_srv_fallback |= var_ign_srv_lookup_err; + break; + case DNS_NULLSRV: + dsb_status(why, "5.1.0"); + break; + case DNS_OK: + /* Shuffle then sort the SRV rr records by priority and weight. */ + srv_names = dns_srv_rr_sort(srv_names); + best_pref = (srv_names ? srv_names->pref : IMPOSSIBLE_PREFERENCE); + addr_list = smtp_addr_list(srv_names, why); + if (mxrr) + *mxrr = dns_rr_copy(srv_names); /* copies one record! */ + dns_rr_free(srv_names); + if (addr_list == 0) { + msg_warn("no SRV host for %s has a valid address record", + str_srv_qname); + break; + } + /* Optional loop prevention, similar to smtp_domain_addr(). */ + best_found = (addr_list ? addr_list->pref : IMPOSSIBLE_PREFERENCE); + if (msg_verbose) + smtp_print_addr(aname, addr_list); + if ((misc_flags & SMTP_MISC_FLAG_LOOP_DETECT) + && (self = smtp_find_self(addr_list)) != 0) { + addr_list = smtp_truncate_self(addr_list, self->pref); + if (addr_list == 0) { + if (best_pref != best_found) { + dsb_simple(why, "4.4.4", + "unable to find primary relay for %s", + str_srv_qname); + } else { + dsb_simple(why, "5.4.6", "mail for %s loops back to myself", + str_srv_qname); + } + } + } + /* TODO: sort by priority, weight, and address family preference. */ + + /* Optional address family balancing, as in smtp_domain_addr(). */ + if (addr_list && addr_list->next) { + if (var_smtp_mxaddr_limit > 0 && var_smtp_balance_inet_proto) + addr_list = smtp_balance_inet_proto(addr_list, misc_flags, + var_smtp_mxaddr_limit); + } + break; + case DNS_NOTFOUND: + dsb_status(why, "5.4.4"); + break; + } + + /* + * If permitted, fall back to non-SRV record lookups. + */ + if (addr_list == 0 && allow_non_srv_fallback) { + msg_info("skipping SRV lookup for %s: %s", + str_srv_qname, STR(why->reason)); + if (misc_flags & SMTP_MISC_FLAG_FALLBACK_SRV_TO_MX) + addr_list = smtp_domain_addr(name, mxrr, misc_flags, why, + found_myself); + else + addr_list = smtp_host_addr(name, misc_flags, why); + } + + /* + * Only if we're not falling back. + */ + else { + *found_myself |= (self != 0); + } + return (addr_list); +} diff --git a/src/smtp/smtp_addr.h b/src/smtp/smtp_addr.h index 8f20961..3d70413 100644 --- a/src/smtp/smtp_addr.h +++ b/src/smtp/smtp_addr.h @@ -18,6 +18,7 @@ */ extern DNS_RR *smtp_host_addr(const char *, int, DSN_BUF *); extern DNS_RR *smtp_domain_addr(const char *, DNS_RR **, int, DSN_BUF *, int *); +extern DNS_RR *smtp_service_addr(const char *, const char *, DNS_RR **, int, DSN_BUF *, int *); /* LICENSE /* .ad diff --git a/src/smtp/smtp_connect.c b/src/smtp/smtp_connect.c index 4d48883..4b3153f 100644 --- a/src/smtp/smtp_connect.c +++ b/src/smtp/smtp_connect.c @@ -28,7 +28,8 @@ /* destinations may be specified as "unix:pathname", "inet:host" /* or "inet:host:port". /* -/* With SMTP, the Internet domain name service is queried for mail +/* With SMTP, or with SRV record lookup enabled, the Internet +/* domain name service is queried for mail /* exchanger hosts. Quote the domain name with `[' and `]' to /* suppress mail exchanger lookups. /* @@ -333,7 +334,8 @@ static SMTP_SESSION *smtp_connect_sock(int sock, struct sockaddr *sa, /* smtp_parse_destination - parse host/port destination */ static char *smtp_parse_destination(char *destination, char *def_service, - char **hostp, unsigned *portp) + char **hostp, char **servicep, + unsigned *portp) { char *buf = mystrdup(destination); char *service; @@ -349,12 +351,13 @@ static char *smtp_parse_destination(char *destination, char *def_service, * Parse the host/port information. We're working with a copy of the * destination argument so the parsing can be destructive. */ - if ((err = host_port(buf, hostp, (char *) 0, &service, def_service)) != 0) + if ((err = host_port(buf, hostp, (char *) 0, servicep, def_service)) != 0) msg_fatal("%s in server description: %s", err, destination); /* * Convert service to port number, network byte order. */ + service = *servicep; if (alldig(service)) { if ((port = atoi(service)) >= 65536 || port == 0) msg_fatal("bad network port in destination: %s", destination); @@ -635,6 +638,9 @@ static void smtp_update_addr_list(DNS_RR **addr_list, const char *server_addr, * XXX Extend the SMTP_SESSION structure with sockaddr information so that * we can avoid repeated string->binary transformations for the same * address. + * + * XXX SRV support: this should match the port, too, otherwise we may + * eliminate too many list entries. */ if ((aierr = hostaddr_to_sockaddr(server_addr, (char *) 0, 0, &res0)) != 0) { msg_warn("hostaddr_to_sockaddr %s: %s", @@ -665,6 +671,18 @@ static int smtp_reuse_session(SMTP_STATE *state, DNS_RR **addr_list, DSN_BUF *why = state->why; /* + * This code is called after server address/port lookup, before + * iter->host, iter->addr, iter->rr and iter->mx are assigned concrete + * values, and while iter->port still corresponds to the nexthop service, + * or the default service configured with smtp_tcp_port or lmtp_tcp_port. + * + * When a connection is reused by nexthop/service or by server address/port, + * iter->host, iter->addr and iter->port are updated with actual values + * from the cached session. Additionally, when a connection is searched + * by nexthop/service, iter->rr remains null, and when a connection is + * searched by server address/port, iter->rr is updated with an actual + * server address/port before the search is made. + * * First, search the cache by delivery request nexthop. We truncate the * server address list when all the sessions for this destination are * used up, to reduce the number of variables that need to be checked @@ -731,9 +749,7 @@ static int smtp_reuse_session(SMTP_STATE *state, DNS_RR **addr_list, /* XXX Assume there is no code at the end of this loop. */ continue; } - vstring_strcpy(iter->addr, hostaddr.buf); - vstring_strcpy(iter->host, SMTP_HNAME(addr)); - iter->rr = addr; + SMTP_ITER_UPDATE_HOST(iter, SMTP_HNAME(addr), hostaddr.buf, addr); #ifdef USE_TLS if (!smtp_tls_policy_cache_query(why, state->tls, iter)) { msg_warn("TLS policy lookup error for %s/%s: %s", @@ -818,6 +834,7 @@ static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, char *dest_buf; char *domain; unsigned port; + char *service; DNS_RR *addr_list; DNS_RR *addr; DNS_RR *next; @@ -825,6 +842,8 @@ static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, int sess_count; SMTP_SESSION *session; int lookup_mx; + int non_dns_or_literal; + int i_am_mx; unsigned domain_best_pref; MAI_HOSTADDR_STR hostaddr; @@ -834,8 +853,28 @@ static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, /* * Parse the destination. If no TCP port is specified, use the port * that is reserved for the protocol (SMTP or LMTP). + * + * The 'service' variable corresponds to the remote service specified + * with the nexthop, or the default service configured with + * smtp_tcp_port or lmtp_tcp_port. The 'port' variable and + * SMTP_ITERATOR.port initially correspond to that service. This + * determines what loop prevention will be in effect. + * + * The SMTP_ITERATOR.port will be overwritten after SRV record lookup. + * This guarantees that the connection cache key contains the correct + * port value when caching and retrieving a connection by its server + * address (and port). + * + * By design, the connection cache key contains NO port information when + * caching or retrieving a connection by its nexthop destination. + * Instead, the cache key contains the master.cf service name (a + * proxy for all the parameter settings including the default service + * from smtp_tcp_port or lmtp_tcp_port), together with the nexthop + * destination and sender-dependent info. This should be sufficient + * to avoid cross talk between mail streams that should be separated. */ - dest_buf = smtp_parse_destination(dest, def_service, &domain, &port); + dest_buf = smtp_parse_destination(dest, def_service, &domain, + &service, &port); if (var_helpful_warnings && var_smtp_tls_wrappermode == 0 && ntohs(port) == 465) { msg_info("SMTPS wrappermode (TCP port 465) requires setting " @@ -848,32 +887,48 @@ static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, SMTP_ITER_INIT(iter, dest, NO_HOST, NO_ADDR, port, state); /* - * Resolve an SMTP or LMTP server. In the case of SMTP, skip mail - * exchanger lookups when a quoted host is specified or when DNS - * lookups are disabled. + * Resolve an SMTP or LMTP server. Skip MX or SRV lookups when a + * quoted domain is specified or when DNS lookups are disabled. */ if (msg_verbose) - msg_info("connecting to %s port %d", domain, ntohs(port)); + msg_info("connecting to %s service %s", domain, service); + non_dns_or_literal = (smtp_dns_support == SMTP_DNS_DISABLED + || *dest == '['); if (smtp_mode) { if (ntohs(port) == IPPORT_SMTP) state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT; else state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT; - lookup_mx = (smtp_dns_support != SMTP_DNS_DISABLED && *dest != '['); + lookup_mx = !non_dns_or_literal; } else lookup_mx = 0; - if (!lookup_mx) { + + /* + * Look up SRV and address records and fall back to non-SRV lookups + * if permitted by configuration settings, or look up MX and address + * records, or look up address records only. + */ + i_am_mx = 0; + addr_list = 0; + if (!non_dns_or_literal && smtp_use_srv_lookup + && string_list_match(smtp_use_srv_lookup, service)) { + if (lookup_mx) + state->misc_flags |= SMTP_MISC_FLAG_FALLBACK_SRV_TO_MX; + else + state->misc_flags &= ~SMTP_MISC_FLAG_FALLBACK_SRV_TO_MX; + addr_list = smtp_service_addr(domain, service, &iter->mx, + state->misc_flags, why, &i_am_mx); + } else if (!lookup_mx) { + /* Non-DNS, literal, or non-SMTP service */ addr_list = smtp_host_addr(domain, state->misc_flags, why); /* XXX We could be an MX host for this destination... */ } else { - int i_am_mx = 0; - addr_list = smtp_domain_addr(domain, &iter->mx, state->misc_flags, why, &i_am_mx); - /* If we're MX host, don't connect to non-MX backups. */ - if (i_am_mx) - state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; } + /* If we're MX host, don't connect to non-MX backups. */ + if (i_am_mx) + state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; /* * Don't try fall-back hosts if mail loops to myself. That would just @@ -966,9 +1021,7 @@ static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, /* XXX Assume there is no code at the end of this loop. */ continue; } - vstring_strcpy(iter->addr, hostaddr.buf); - vstring_strcpy(iter->host, SMTP_HNAME(addr)); - iter->rr = addr; + SMTP_ITER_UPDATE_HOST(iter, SMTP_HNAME(addr), hostaddr.buf, addr); #ifdef USE_TLS if (!smtp_tls_policy_cache_query(why, state->tls, iter)) { msg_warn("TLS policy lookup for %s/%s: %s", diff --git a/src/smtp/smtp_params.c b/src/smtp/smtp_params.c index 561f6a0..b893a76 100644 --- a/src/smtp/smtp_params.c +++ b/src/smtp/smtp_params.c @@ -65,6 +65,7 @@ VAR_SMTP_DSN_FILTER, DEF_SMTP_DSN_FILTER, &var_smtp_dsn_filter, 0, 0, VAR_SMTP_DNS_RE_FILTER, DEF_SMTP_DNS_RE_FILTER, &var_smtp_dns_re_filter, 0, 0, VAR_TLSPROXY_SERVICE, DEF_TLSPROXY_SERVICE, &var_tlsproxy_service, 1, 0, + VAR_USE_SRV_LOOKUP, DEF_USE_SRV_LOOKUP, &var_use_srv_lookup, 0, 0, 0, }; static const CONFIG_TIME_TABLE smtp_time_table[] = { @@ -130,5 +131,7 @@ VAR_SMTP_REC_DEADLINE, DEF_SMTP_REC_DEADLINE, &var_smtp_rec_deadline, VAR_SMTP_DUMMY_MAIL_AUTH, DEF_SMTP_DUMMY_MAIL_AUTH, &var_smtp_dummy_mail_auth, VAR_SMTP_BALANCE_INET_PROTO, DEF_SMTP_BALANCE_INET_PROTO, &var_smtp_balance_inet_proto, + VAR_IGN_SRV_LOOKUP_ERR, DEF_IGN_SRV_LOOKUP_ERR, &var_ign_srv_lookup_err, + VAR_ALLOW_SRV_FALLBACK, DEF_ALLOW_SRV_FALLBACK, &var_allow_srv_fallback, 0, }; diff --git a/src/smtp/smtp_session.c b/src/smtp/smtp_session.c index 1b3a20e..3ac4ccc 100644 --- a/src/smtp/smtp_session.c +++ b/src/smtp/smtp_session.c @@ -129,6 +129,7 @@ #define SESS_ATTR_DEST "destination" #define SESS_ATTR_HOST "host_name" #define SESS_ATTR_ADDR "host_addr" +#define SESS_ATTR_PORT "host_port" #define SESS_ATTR_DEST_FEATURES "destination_features" #define SESS_ATTR_TLS_LEVEL "tls_level" @@ -258,6 +259,7 @@ int smtp_session_passivate(SMTP_SESSION *session, VSTRING *dest_prop, SEND_ATTR_STR(SESS_ATTR_DEST, STR(iter->dest)), SEND_ATTR_STR(SESS_ATTR_HOST, STR(iter->host)), SEND_ATTR_STR(SESS_ATTR_ADDR, STR(iter->addr)), + SEND_ATTR_UINT(SESS_ATTR_PORT, iter->port), SEND_ATTR_INT(SESS_ATTR_DEST_FEATURES, session->features & SMTP_FEATURE_DESTINATION_MASK), ATTR_TYPE_END) != 0 @@ -397,9 +399,10 @@ SMTP_SESSION *smtp_session_activate(int fd, SMTP_ITERATOR *iter, RECV_ATTR_STR(SESS_ATTR_DEST, iter->dest), RECV_ATTR_STR(SESS_ATTR_HOST, iter->host), RECV_ATTR_STR(SESS_ATTR_ADDR, iter->addr), + RECV_ATTR_UINT(SESS_ATTR_PORT, &iter->port), RECV_ATTR_INT(SESS_ATTR_DEST_FEATURES, &dest_features), - ATTR_TYPE_END) != 4 + ATTR_TYPE_END) != 5 || vstream_fclose(mp) != 0) { msg_warn("smtp_session_passivate: bad cached dest properties"); SMTP_SESSION_ACTIVATE_ERR_RETURN(); diff --git a/src/smtpd/smtpd_check.c b/src/smtpd/smtpd_check.c index 85d5944..a60e878 100644 --- a/src/smtpd/smtpd_check.c +++ b/src/smtpd/smtpd_check.c @@ -3056,8 +3056,8 @@ static int check_server_access(SMTPD_STATE *state, const char *table, || type == T_AAAA #endif ) { - server_list = dns_rr_create(domain, domain, T_MX, C_IN, 0, 0, - domain, strlen(domain) + 1); + server_list = dns_rr_create_nopref(domain, domain, T_MX, C_IN, 0, + domain, strlen(domain) + 1); } else { dns_status = dns_lookup(domain, type, 0, &server_list, (VSTRING *) 0, (VSTRING *) 0); @@ -3065,8 +3065,8 @@ static int check_server_access(SMTPD_STATE *state, const char *table, return (SMTPD_CHECK_DUNNO); if (dns_status == DNS_NOTFOUND /* Not: h_errno == NO_DATA */ ) { if (type == T_MX) { - server_list = dns_rr_create(domain, domain, type, C_IN, 0, 0, - domain, strlen(domain) + 1); + server_list = dns_rr_create_nopref(domain, domain, type, C_IN, + 0, domain, strlen(domain) + 1); dns_status = DNS_OK; } else if (type == T_NS /* && h_errno == NO_DATA */ ) { while ((domain = strchr(domain, '.')) != 0 && domain[1]) { diff --git a/src/util/attr.h b/src/util/attr.h index dc6f9f7..a890a5b 100644 --- a/src/util/attr.h +++ b/src/util/attr.h @@ -61,6 +61,7 @@ typedef int (*ATTR_PRINT_SLAVE_FN) (ATTR_PRINT_MASTER_FN, VSTREAM *, int, void * * for documentation. */ #define SEND_ATTR_INT(name, val) ATTR_TYPE_INT, CHECK_CPTR(ATTR, char, (name)), CHECK_VAL(ATTR, int, (val)) +#define SEND_ATTR_UINT(name, val) ATTR_TYPE_INT, CHECK_CPTR(ATTR, char, (name)), CHECK_VAL(ATTR, unsigned, (val)) #define SEND_ATTR_STR(name, val) ATTR_TYPE_STR, CHECK_CPTR(ATTR, char, (name)), CHECK_CPTR(ATTR, char, (val)) #define SEND_ATTR_HASH(val) ATTR_TYPE_HASH, CHECK_CPTR(ATTR, HTABLE, (val)) #define SEND_ATTR_NV(val) ATTR_TYPE_NV, CHECK_CPTR(ATTR, NVTABLE, (val)) @@ -69,6 +70,7 @@ typedef int (*ATTR_PRINT_SLAVE_FN) (ATTR_PRINT_MASTER_FN, VSTREAM *, int, void * #define SEND_ATTR_FUNC(func, val) ATTR_TYPE_FUNC, CHECK_VAL(ATTR, ATTR_PRINT_SLAVE_FN, (func)), CHECK_CPTR(ATTR, void, (val)) #define RECV_ATTR_INT(name, val) ATTR_TYPE_INT, CHECK_CPTR(ATTR, char, (name)), CHECK_PTR(ATTR, int, (val)) +#define RECV_ATTR_UINT(name, val) ATTR_TYPE_INT, CHECK_CPTR(ATTR, char, (name)), CHECK_PTR(ATTR, unsigned, (val)) #define RECV_ATTR_STR(name, val) ATTR_TYPE_STR, CHECK_CPTR(ATTR, char, (name)), CHECK_PTR(ATTR, VSTRING, (val)) #define RECV_ATTR_HASH(val) ATTR_TYPE_HASH, CHECK_PTR(ATTR, HTABLE, (val)) #define RECV_ATTR_NV(val) ATTR_TYPE_NV, CHECK_PTR(ATTR, NVTABLE, (val)) @@ -79,9 +81,11 @@ typedef int (*ATTR_PRINT_SLAVE_FN) (ATTR_PRINT_MASTER_FN, VSTREAM *, int, void * CHECK_VAL_HELPER_DCL(ATTR, ssize_t); CHECK_VAL_HELPER_DCL(ATTR, long); CHECK_VAL_HELPER_DCL(ATTR, int); +CHECK_VAL_HELPER_DCL(ATTR, unsigned); CHECK_PTR_HELPER_DCL(ATTR, void); CHECK_PTR_HELPER_DCL(ATTR, long); CHECK_PTR_HELPER_DCL(ATTR, int); +CHECK_PTR_HELPER_DCL(ATTR, unsigned); CHECK_PTR_HELPER_DCL(ATTR, VSTRING); CHECK_PTR_HELPER_DCL(ATTR, NVTABLE); CHECK_PTR_HELPER_DCL(ATTR, HTABLE);