external/ibm-public/postfix/dist/src/smtp/smtp_reuse.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      smtp_reuse 3
   6 /* SUMMARY
   7 /*      SMTP session cache glue
   8 /* SYNOPSIS
   9 /*      #include <smtp.h>
  10 /*      #include <smtp_reuse.h>
  11 /*
  12 /*      void    smtp_save_session(state)
  13 /*      SMTP_STATE *state;
  14 /*
  15 /*      SMTP_SESSION *smtp_reuse_domain(state, lookup_mx, domain, port)
  16 /*      SMTP_STATE *state;
  17 /*      int     lookup_mx;
  18 /*      char    *domain;
  19 /*      unsigned port;
  20 /*
  21 /*      SMTP_SESSION *smtp_reuse_addr(state, addr, port)
  22 /*      SMTP_STATE *state;
  23 /*      const char *addr;
  24 /*      unsigned port;
  25 /* DESCRIPTION
  26 /*      This module implements the SMTP client specific interface to
  27 /*      the generic session cache infrastructure.
  28 /*
  29 /*      smtp_save_session() stores the current session under the
  30 /*      next-hop logical destination (if available) and under the
  31 /*      remote server address.  The SMTP_SESSION object is destroyed.
  32 /*
  33 /*      smtp_reuse_domain() looks up a cached session by its logical
  34 /*      destination, and verifies that the session is still alive.
  35 /*      The restored session information includes the "best MX" bit.
  36 /*      The result is null in case of failure.
  37 /*
  38 /*      smtp_reuse_addr() looks up a cached session by its server
  39 /*      address, and verifies that the session is still alive.
  40 /*      This operation is disabled when the legacy tls_per_site
  41 /*      or smtp_sasl_password_maps features are enabled.
  42 /*      The result is null in case of failure.
  43 /*
  44 /*      Arguments:
  45 /* .IP state
  46 /*      SMTP client state, including the current session, the original
  47 /*      next-hop domain, etc.
  48 /* .IP lookup_mx
  49 /*      Whether or not the domain is subject to MX lookup.
  50 /* .IP domain
  51 /*      Domain name or bare numerical address.
  52 /* .IP addr
  53 /*      The remote server address as printable text.
  54 /* .IP port
  55 /*      The remote server port, network byte order.
  56 /* LICENSE
  57 /* .ad
  58 /* .fi
  59 /*      The Secure Mailer license must be distributed with this software.
  60 /* AUTHOR(S)
  61 /*      Wietse Venema
  62 /*      IBM T.J. Watson Research
  63 /*      P.O. Box 704
  64 /*      Yorktown Heights, NY 10598, USA
  65 /*--*/
  66
  67 /* System library. */
  68
  69 #include <sys_defs.h>
  70 #include <sys/socket.h>
  71 #include <netinet/in.h>
  72 #include <arpa/inet.h>
  73 #include <unistd.h>
  74 #include <string.h>
  75
  76 /* Utility library. */
  77
  78 #include <msg.h>
  79 #include <mymalloc.h>
  80 #include <vstream.h>
  81 #include <vstring.h>
  82 #include <htable.h>
  83 #include <stringops.h>
  84
  85 /* Global library. */
  86
  87 #include <scache.h>
  88 #include <mail_params.h>
  89
  90 /* Application-specific. */
  91
  92 #include <smtp.h>
  93 #include <smtp_reuse.h>
  94
  95  /*
  96   * We encode the MX lookup/A lookup method into the name under which SMTP
  97   * session information is cached. The following macros serve to make the
  98   * remainder of the code less obscure.
  99   */
 100 #define NO_MX_LOOKUP    0
 101
 102 #define SMTP_SCACHE_LABEL(mx_lookup_flag) \
 103         ((mx_lookup_flag) ? "%s:%s:%u" : "%s:[%s]:%u")
 104
 105 /* smtp_save_session - save session under next-hop name and server address */
 106
 107 void    smtp_save_session(SMTP_STATE *state)
 108 {
 109     SMTP_SESSION *session = state->session;
 110     int     fd;
 111
 112     /*
 113      * Encode the next-hop logical destination, if available. Reuse storage
 114      * that is also used for cache lookup queries.
 115      *
 116      * Note: if the label needs to be made more specific (with e.g., SASL login
 117      * information), just append the text with vstring_sprintf_append().
 118      */
 119     if (HAVE_NEXTHOP_STATE(state))
 120         vstring_sprintf(state->dest_label,
 121                         SMTP_SCACHE_LABEL(state->nexthop_lookup_mx),
 122                         state->service, state->nexthop_domain,
 123                         ntohs(state->nexthop_port));
 124
 125     /*
 126      * Encode the physical endpoint name. Reuse storage that is also used for
 127      * cache lookup queries.
 128      *
 129      * Note: if the label needs to be made more specific (with e.g., SASL login
 130      * information), just append the text with vstring_sprintf_append().
 131      */
 132     vstring_sprintf(state->endp_label,
 133                     SMTP_SCACHE_LABEL(NO_MX_LOOKUP),
 134                     state->service, session->addr, ntohs(session->port));
 135
 136     /*
 137      * Passivate the SMTP_SESSION object, destroying the object in the
 138      * process. Reuse storage that is also used for cache lookup results.
 139      */
 140     fd = smtp_session_passivate(session, state->dest_prop, state->endp_prop);
 141     state->session = 0;
 142
 143     /*
 144      * Save the session under the next-hop name, if available.
 145      *
 146      * XXX The logical to physical binding can be kept for as long as the DNS
 147      * allows us to (but that could result in the caching of lots of unused
 148      * bindings). The session should be idle for no more than 30 seconds or
 149      * so.
 150      */
 151     if (HAVE_NEXTHOP_STATE(state))
 152         scache_save_dest(smtp_scache, var_smtp_cache_conn, STR(state->dest_label),
 153                          STR(state->dest_prop), STR(state->endp_label));
 154
 155     /*
 156      * Save every good session under its physical endpoint address.
 157      */
 158     scache_save_endp(smtp_scache, var_smtp_cache_conn, STR(state->endp_label),
 159                      STR(state->endp_prop), fd);
 160 }
 161
 162 /* smtp_reuse_common - common session reuse code */
 163
 164 static SMTP_SESSION *smtp_reuse_common(SMTP_STATE *state, int fd,
 165                                                const char *label)
 166 {
 167     const char *myname = "smtp_reuse_common";
 168     SMTP_SESSION *session;
 169
 170     /*
 171      * Re-activate the SMTP_SESSION object.
 172      */
 173     session = smtp_session_activate(fd, state->dest_prop, state->endp_prop);
 174     if (session == 0) {
 175         msg_warn("%s: bad cached session attribute for %s", myname, label);
 176         (void) close(fd);
 177         return (0);
 178     }
 179     state->session = session;
 180     session->state = state;
 181
 182     /*
 183      * XXX Temporary fix.
 184      *
 185      * Cached connections are always plaintext. They must never be reused when
 186      * TLS encryption is required.
 187      *
 188      * As long as we support the legacy smtp_tls_per_site feature, we must
 189      * search the connection cache before making TLS policy decisions. This
 190      * is because the policy can depend on the server name. For example, a
 191      * site could have a global policy that requires encryption, with
 192      * per-server exceptions that allow plaintext.
 193      *
 194      * With the newer smtp_tls_policy_maps feature, the policy depends on the
 195      * next-hop destination only. We can avoid unnecessary connection cache
 196      * lookups, because we can compute the TLS policy much earlier.
 197      */
 198 #ifdef USE_TLS
 199     if (session->tls_level >= TLS_LEV_ENCRYPT) {
 200         if (msg_verbose)
 201             msg_info("%s: skipping plain-text cached session to %s",
 202                      myname, label);
 203         smtp_quit(state);                       /* Close politely */
 204         smtp_session_free(session);             /* And avoid leaks */
 205         return (state->session = 0);
 206     }
 207 #endif
 208
 209     /*
 210      * Send an RSET probe to verify that the session is still good.
 211      */
 212     if (smtp_rset(state) < 0
 213         || (session->features & SMTP_FEATURE_RSET_REJECTED) != 0) {
 214         smtp_session_free(session);
 215         return (state->session = 0);
 216     }
 217
 218     /*
 219      * Avoid poor performance when TCP MSS > VSTREAM_BUFSIZE.
 220      */
 221     vstream_tweak_sock(session->stream);
 222
 223     /*
 224      * Update the list of used cached addresses.
 225      */
 226     htable_enter(state->cache_used, session->addr, (char *) 0);
 227
 228     return (session);
 229 }
 230
 231 /* smtp_reuse_domain - reuse session cached under domain name */
 232
 233 SMTP_SESSION *smtp_reuse_domain(SMTP_STATE *state, int lookup_mx,
 234                                         const char *domain, unsigned port)
 235 {
 236     SMTP_SESSION *session;
 237     int     fd;
 238
 239     /*
 240      * Look up the session by its logical name.
 241      *
 242      * Note: if the label needs to be made more specific (with e.g., SASL login
 243      * information), just append the text with vstring_sprintf_append().
 244      */
 245     vstring_sprintf(state->dest_label, SMTP_SCACHE_LABEL(lookup_mx),
 246                     state->service, domain, ntohs(port));
 247     if ((fd = scache_find_dest(smtp_scache, STR(state->dest_label),
 248                                state->dest_prop, state->endp_prop)) < 0)
 249         return (0);
 250
 251     /*
 252      * Re-activate the SMTP_SESSION object, and verify that the session is
 253      * still good.
 254      */
 255     session = smtp_reuse_common(state, fd, STR(state->dest_label));
 256     return (session);
 257 }
 258
 259 /* smtp_reuse_addr - reuse session cached under numerical address */
 260
 261 SMTP_SESSION *smtp_reuse_addr(SMTP_STATE *state, const char *addr,
 262                                       unsigned port)
 263 {
 264     SMTP_SESSION *session;
 265     int     fd;
 266
 267     /*
 268      * XXX Disable connection cache lookup by server IP address when the
 269      * tls_per_site policy or smtp_sasl_password_maps features are enabled.
 270      * This connection may have been created under a different hostname that
 271      * resolves to the same IP address. We don't want to use the wrong SASL
 272      * credentials or the wrong TLS policy.
 273      */
 274     if ((var_smtp_tls_per_site && *var_smtp_tls_per_site)
 275         || (var_smtp_sasl_passwd && *var_smtp_sasl_passwd))
 276         return (0);
 277
 278     /*
 279      * Look up the session by its IP address. This means that we have no
 280      * destination-to-address binding properties.
 281      *
 282      * Note: if the label needs to be made more specific (with e.g., SASL login
 283      * information), just append the text with vstring_sprintf_append().
 284      */
 285     vstring_sprintf(state->endp_label, SMTP_SCACHE_LABEL(NO_MX_LOOKUP),
 286                     state->service, addr, ntohs(port));
 287     if ((fd = scache_find_endp(smtp_scache, STR(state->endp_label),
 288                                state->endp_prop)) < 0)
 289         return (0);
 290     VSTRING_RESET(state->dest_prop);
 291     VSTRING_TERMINATE(state->dest_prop);
 292
 293     /*
 294      * Re-activate the SMTP_SESSION object, and verify that the session is
 295      * still good.
 296      */
 297     session = smtp_reuse_common(state, fd, STR(state->endp_label));
 298
 299     /*
 300      * XXX What if hostnames don't match (addr->name versus session->name),
 301      * or if the SASL login name for this host does not match the SASL login
 302      * name that was used when opening this session? If something depends
 303      * critically on such information being identical, then that information
 304      * should be included in the logical and physical labels under which a
 305      * session is cached.
 306      */
 307     return (session);
 308 }