granicus.if.org Git - postgresql/blob - src/backend/libpq/auth.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * auth.c
   4  *        Routines to handle network authentication
   5  *
   6  * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.119 2004/10/12 21:54:38 petere Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "postgres.h"
  17
  18 #include <sys/param.h>
  19 #include <sys/socket.h>
  20 #if defined(HAVE_STRUCT_CMSGCRED) || defined(HAVE_STRUCT_FCRED) || defined(HAVE_STRUCT_SOCKCRED)
  21 #include <sys/uio.h>
  22 #include <sys/ucred.h>
  23 #include <errno.h>
  24 #endif
  25 #include <netinet/in.h>
  26 #include <arpa/inet.h>
  27
  28 #include "libpq/auth.h"
  29 #include "libpq/crypt.h"
  30 #include "libpq/hba.h"
  31 #include "libpq/libpq.h"
  32 #include "libpq/pqcomm.h"
  33 #include "libpq/pqformat.h"
  34 #include "miscadmin.h"
  35 #include "storage/ipc.h"
  36
  37
  38 static void sendAuthRequest(Port *port, AuthRequest areq);
  39 static void auth_failed(Port *port, int status);
  40 static char *recv_password_packet(Port *port);
  41 static int      recv_and_check_password_packet(Port *port);
  42
  43 char       *pg_krb_server_keyfile;
  44
  45 #ifdef USE_PAM
  46 #ifdef HAVE_PAM_PAM_APPL_H
  47 #include <pam/pam_appl.h>
  48 #endif
  49 #ifdef HAVE_SECURITY_PAM_APPL_H
  50 #include <security/pam_appl.h>
  51 #endif
  52
  53 #define PGSQL_PAM_SERVICE "postgresql"  /* Service name passed to PAM */
  54
  55 static int      CheckPAMAuth(Port *port, char *user, char *password);
  56 static int pam_passwd_conv_proc(int num_msg, const struct pam_message ** msg,
  57                                          struct pam_response ** resp, void *appdata_ptr);
  58
  59 static struct pam_conv pam_passw_conv = {
  60         &pam_passwd_conv_proc,
  61         NULL
  62 };
  63
  64 static char *pam_passwd = NULL; /* Workaround for Solaris 2.6 brokenness */
  65 static Port *pam_port_cludge;   /* Workaround for passing "Port *port"
  66                                                                  * into pam_passwd_conv_proc */
  67 #endif   /* USE_PAM */
  68
  69 #ifdef KRB4
  70 /*----------------------------------------------------------------
  71  * MIT Kerberos authentication system - protocol version 4
  72  *----------------------------------------------------------------
  73  */
  74
  75 #include "krb.h"
  76
  77 /*
  78  * pg_krb4_recvauth -- server routine to receive authentication information
  79  *                                         from the client
  80  *
  81  * Nothing unusual here, except that we compare the username obtained from
  82  * the client's setup packet to the authenticated name.  (We have to retain
  83  * the name in the setup packet since we have to retain the ability to handle
  84  * unauthenticated connections.)
  85  */
  86 static int
  87 pg_krb4_recvauth(Port *port)
  88 {
  89         long            krbopts = 0;    /* one-way authentication */
  90         KTEXT_ST        clttkt;
  91         char            instance[INST_SZ + 1],
  92                                 version[KRB_SENDAUTH_VLEN + 1];
  93         AUTH_DAT        auth_data;
  94         Key_schedule key_sched;
  95         int                     status;
  96
  97         strcpy(instance, "*");          /* don't care, but arg gets expanded
  98                                                                  * anyway */
  99         status = krb_recvauth(krbopts,
 100                                                   port->sock,
 101                                                   &clttkt,
 102                                                   PG_KRB_SRVNAM,
 103                                                   instance,
 104                                                   &port->raddr.in,
 105                                                   &port->laddr.in,
 106                                                   &auth_data,
 107                                                   pg_krb_server_keyfile,
 108                                                   key_sched,
 109                                                   version);
 110         if (status != KSUCCESS)
 111         {
 112                 ereport(LOG,
 113                                 (errmsg("Kerberos error: %s", krb_err_txt[status])));
 114                 return STATUS_ERROR;
 115         }
 116         if (strncmp(version, PG_KRB4_VERSION, KRB_SENDAUTH_VLEN) != 0)
 117         {
 118                 ereport(LOG,
 119                                 (errmsg("unexpected Kerberos protocol version received from client (received \"%s\", expected \"%s\")",
 120                                                 version, PG_KRB4_VERSION)));
 121                 return STATUS_ERROR;
 122         }
 123         if (strncmp(port->user_name, auth_data.pname, SM_DATABASE_USER) != 0)
 124         {
 125                 ereport(LOG,
 126                                 (errmsg("unexpected Kerberos user name received from client (received \"%s\", expected \"%s\")",
 127                                                 port->user_name, auth_data.pname)));
 128                 return STATUS_ERROR;
 129         }
 130         return STATUS_OK;
 131 }
 132
 133 #else
 134
 135 static int
 136 pg_krb4_recvauth(Port *port)
 137 {
 138         ereport(LOG,
 139                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 140                          errmsg("Kerberos 4 not implemented on this server")));
 141         return STATUS_ERROR;
 142 }
 143 #endif   /* KRB4 */
 144
 145
 146 #ifdef KRB5
 147 /*----------------------------------------------------------------
 148  * MIT Kerberos authentication system - protocol version 5
 149  *----------------------------------------------------------------
 150  */
 151
 152 #include <krb5.h>
 153 #include <com_err.h>
 154
 155 /*
 156  * pg_an_to_ln -- return the local name corresponding to an authentication
 157  *                                name
 158  *
 159  * XXX Assumes that the first aname component is the user name.  This is NOT
 160  *         necessarily so, since an aname can actually be something out of your
 161  *         worst X.400 nightmare, like
 162  *                ORGANIZATION=U. C. Berkeley/NAME=Paul M. Aoki@CS.BERKELEY.EDU
 163  *         Note that the MIT an_to_ln code does the same thing if you don't
 164  *         provide an aname mapping database...it may be a better idea to use
 165  *         krb5_an_to_ln, except that it punts if multiple components are found,
 166  *         and we can't afford to punt.
 167  */
 168 static char *
 169 pg_an_to_ln(char *aname)
 170 {
 171         char       *p;
 172
 173         if ((p = strchr(aname, '/')) || (p = strchr(aname, '@')))
 174                 *p = '\0';
 175         return aname;
 176 }
 177
 178
 179 /*
 180  * Various krb5 state which is not connection specfic, and a flag to
 181  * indicate whether we have initialised it yet.
 182  */
 183 static int      pg_krb5_initialised;
 184 static krb5_context pg_krb5_context;
 185 static krb5_keytab pg_krb5_keytab;
 186 static krb5_principal pg_krb5_server;
 187
 188
 189 static int
 190 pg_krb5_init(void)
 191 {
 192         krb5_error_code retval;
 193
 194         if (pg_krb5_initialised)
 195                 return STATUS_OK;
 196
 197         retval = krb5_init_context(&pg_krb5_context);
 198         if (retval)
 199         {
 200                 ereport(LOG,
 201                                 (errmsg("Kerberos initialization returned error %d",
 202                                                 retval)));
 203                 com_err("postgres", retval, "while initializing krb5");
 204                 return STATUS_ERROR;
 205         }
 206
 207         retval = krb5_kt_resolve(pg_krb5_context, pg_krb_server_keyfile, &pg_krb5_keytab);
 208         if (retval)
 209         {
 210                 ereport(LOG,
 211                                 (errmsg("Kerberos keytab resolving returned error %d",
 212                                                 retval)));
 213                 com_err("postgres", retval, "while resolving keytab file \"%s\"",
 214                                 pg_krb_server_keyfile);
 215                 krb5_free_context(pg_krb5_context);
 216                 return STATUS_ERROR;
 217         }
 218
 219         retval = krb5_sname_to_principal(pg_krb5_context, NULL, PG_KRB_SRVNAM,
 220                                                                          KRB5_NT_SRV_HST, &pg_krb5_server);
 221         if (retval)
 222         {
 223                 ereport(LOG,
 224                  (errmsg("Kerberos sname_to_principal(\"%s\") returned error %d",
 225                                  PG_KRB_SRVNAM, retval)));
 226                 com_err("postgres", retval,
 227                                 "while getting server principal for service \"%s\"",
 228                                 PG_KRB_SRVNAM);
 229                 krb5_kt_close(pg_krb5_context, pg_krb5_keytab);
 230                 krb5_free_context(pg_krb5_context);
 231                 return STATUS_ERROR;
 232         }
 233
 234         pg_krb5_initialised = 1;
 235         return STATUS_OK;
 236 }
 237
 238
 239 /*
 240  * pg_krb5_recvauth -- server routine to receive authentication information
 241  *                                         from the client
 242  *
 243  * We still need to compare the username obtained from the client's setup
 244  * packet to the authenticated name, as described in pg_krb4_recvauth.  This
 245  * is a bit more problematic in v5, as described above in pg_an_to_ln.
 246  *
 247  * We have our own keytab file because postgres is unlikely to run as root,
 248  * and so cannot read the default keytab.
 249  */
 250 static int
 251 pg_krb5_recvauth(Port *port)
 252 {
 253         krb5_error_code retval;
 254         int                     ret;
 255         krb5_auth_context auth_context = NULL;
 256         krb5_ticket *ticket;
 257         char       *kusername;
 258
 259         ret = pg_krb5_init();
 260         if (ret != STATUS_OK)
 261                 return ret;
 262
 263         retval = krb5_recvauth(pg_krb5_context, &auth_context,
 264                                                    (krb5_pointer) & port->sock, PG_KRB_SRVNAM,
 265                                                    pg_krb5_server, 0, pg_krb5_keytab, &ticket);
 266         if (retval)
 267         {
 268                 ereport(LOG,
 269                                 (errmsg("Kerberos recvauth returned error %d",
 270                                                 retval)));
 271                 com_err("postgres", retval, "from krb5_recvauth");
 272                 return STATUS_ERROR;
 273         }
 274
 275         /*
 276          * The "client" structure comes out of the ticket and is therefore
 277          * authenticated.  Use it to check the username obtained from the
 278          * postmaster startup packet.
 279          *
 280          * I have no idea why this is considered necessary.
 281          */
 282 #if defined(HAVE_KRB5_TICKET_ENC_PART2)
 283         retval = krb5_unparse_name(pg_krb5_context,
 284                                                            ticket->enc_part2->client, &kusername);
 285 #elif defined(HAVE_KRB5_TICKET_CLIENT)
 286         retval = krb5_unparse_name(pg_krb5_context,
 287                                                            ticket->client, &kusername);
 288 #else
 289 #error "bogus configuration"
 290 #endif
 291         if (retval)
 292         {
 293                 ereport(LOG,
 294                                 (errmsg("Kerberos unparse_name returned error %d",
 295                                                 retval)));
 296                 com_err("postgres", retval, "while unparsing client name");
 297                 krb5_free_ticket(pg_krb5_context, ticket);
 298                 krb5_auth_con_free(pg_krb5_context, auth_context);
 299                 return STATUS_ERROR;
 300         }
 301
 302         kusername = pg_an_to_ln(kusername);
 303         if (strncmp(port->user_name, kusername, SM_DATABASE_USER))
 304         {
 305                 ereport(LOG,
 306                                 (errmsg("unexpected Kerberos user name received from client (received \"%s\", expected \"%s\")",
 307                                                 port->user_name, kusername)));
 308                 ret = STATUS_ERROR;
 309         }
 310         else
 311                 ret = STATUS_OK;
 312
 313         krb5_free_ticket(pg_krb5_context, ticket);
 314         krb5_auth_con_free(pg_krb5_context, auth_context);
 315         free(kusername);
 316
 317         return ret;
 318 }
 319
 320 #else
 321
 322 static int
 323 pg_krb5_recvauth(Port *port)
 324 {
 325         ereport(LOG,
 326                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 327                          errmsg("Kerberos 5 not implemented on this server")));
 328         return STATUS_ERROR;
 329 }
 330 #endif   /* KRB5 */
 331
 332
 333 /*
 334  * Tell the user the authentication failed, but not (much about) why.
 335  *
 336  * There is a tradeoff here between security concerns and making life
 337  * unnecessarily difficult for legitimate users.  We would not, for example,
 338  * want to report the password we were expecting to receive...
 339  * But it seems useful to report the username and authorization method
 340  * in use, and these are items that must be presumed known to an attacker
 341  * anyway.
 342  * Note that many sorts of failure report additional information in the
 343  * postmaster log, which we hope is only readable by good guys.
 344  */
 345 static void
 346 auth_failed(Port *port, int status)
 347 {
 348         const char *errstr;
 349
 350         /*
 351          * If we failed due to EOF from client, just quit; there's no point in
 352          * trying to send a message to the client, and not much point in
 353          * logging the failure in the postmaster log.  (Logging the failure
 354          * might be desirable, were it not for the fact that libpq closes the
 355          * connection unceremoniously if challenged for a password when it
 356          * hasn't got one to send.  We'll get a useless log entry for every
 357          * psql connection under password auth, even if it's perfectly
 358          * successful, if we log STATUS_EOF events.)
 359          */
 360         if (status == STATUS_EOF)
 361                 proc_exit(0);
 362
 363         switch (port->auth_method)
 364         {
 365                 case uaReject:
 366                         errstr = gettext_noop("authentication failed for user \"%s\": host rejected");
 367                         break;
 368                 case uaKrb4:
 369                         errstr = gettext_noop("Kerberos 4 authentication failed for user \"%s\"");
 370                         break;
 371                 case uaKrb5:
 372                         errstr = gettext_noop("Kerberos 5 authentication failed for user \"%s\"");
 373                         break;
 374                 case uaTrust:
 375                         errstr = gettext_noop("\"trust\" authentication failed for user \"%s\"");
 376                         break;
 377                 case uaIdent:
 378                         errstr = gettext_noop("Ident authentication failed for user \"%s\"");
 379                         break;
 380                 case uaMD5:
 381                 case uaCrypt:
 382                 case uaPassword:
 383                         errstr = gettext_noop("password authentication failed for user \"%s\"");
 384                         break;
 385 #ifdef USE_PAM
 386                 case uaPAM:
 387                         errstr = gettext_noop("PAM authentication failed for user \"%s\"");
 388                         break;
 389 #endif   /* USE_PAM */
 390                 default:
 391                         errstr = gettext_noop("authentication failed for user \"%s\": invalid authentication method");
 392                         break;
 393         }
 394
 395         ereport(FATAL,
 396                         (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 397                          errmsg(errstr, port->user_name)));
 398         /* doesn't return */
 399 }
 400
 401
 402 /*
 403  * Client authentication starts here.  If there is an error, this
 404  * function does not return and the backend process is terminated.
 405  */
 406 void
 407 ClientAuthentication(Port *port)
 408 {
 409         int                     status = STATUS_ERROR;
 410
 411         /*
 412          * Get the authentication method to use for this frontend/database
 413          * combination.  Note: a failure return indicates a problem with the
 414          * hba config file, not with the request.  hba.c should have dropped
 415          * an error message into the postmaster logfile if it failed.
 416          */
 417         if (hba_getauthmethod(port) != STATUS_OK)
 418                 ereport(FATAL,
 419                                 (errcode(ERRCODE_CONFIG_FILE_ERROR),
 420                                  errmsg("missing or erroneous pg_hba.conf file"),
 421                                  errhint("See server log for details.")));
 422
 423         switch (port->auth_method)
 424         {
 425                 case uaReject:
 426
 427                         /*
 428                          * This could have come from an explicit "reject" entry in
 429                          * pg_hba.conf, but more likely it means there was no matching
 430                          * entry.  Take pity on the poor user and issue a helpful
 431                          * error message.  NOTE: this is not a security breach,
 432                          * because all the info reported here is known at the frontend
 433                          * and must be assumed known to bad guys. We're merely helping
 434                          * out the less clueful good guys.
 435                          */
 436                         {
 437                                 char            hostinfo[NI_MAXHOST];
 438
 439                                 getnameinfo_all(&port->raddr.addr, port->raddr.salen,
 440                                                                 hostinfo, sizeof(hostinfo),
 441                                                                 NULL, 0,
 442                                                                 NI_NUMERICHOST);
 443
 444 #ifdef USE_SSL
 445                                 ereport(FATAL,
 446                                    (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 447                                         errmsg("no pg_hba.conf entry for host \"%s\", user \"%s\", database \"%s\", %s",
 448                                                    hostinfo, port->user_name, port->database_name,
 449                                    port->ssl ? gettext("SSL on") : gettext("SSL off"))));
 450 #else
 451                                 ereport(FATAL,
 452                                    (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 453                                         errmsg("no pg_hba.conf entry for host \"%s\", user \"%s\", database \"%s\"",
 454                                            hostinfo, port->user_name, port->database_name)));
 455 #endif
 456                                 break;
 457                         }
 458
 459                 case uaKrb4:
 460                         /* Kerberos 4 only seems to work with AF_INET. */
 461                         if (port->raddr.addr.ss_family != AF_INET
 462                                 || port->laddr.addr.ss_family != AF_INET)
 463                                 ereport(FATAL,
 464                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 465                                    errmsg("Kerberos 4 only supports IPv4 connections")));
 466                         sendAuthRequest(port, AUTH_REQ_KRB4);
 467                         status = pg_krb4_recvauth(port);
 468                         break;
 469
 470                 case uaKrb5:
 471                         sendAuthRequest(port, AUTH_REQ_KRB5);
 472                         status = pg_krb5_recvauth(port);
 473                         break;
 474
 475                 case uaIdent:
 476
 477                         /*
 478                          * If we are doing ident on unix-domain sockets, use SCM_CREDS
 479                          * only if it is defined and SO_PEERCRED isn't.
 480                          */
 481 #if !defined(HAVE_GETPEEREID) && !defined(SO_PEERCRED) && \
 482         (defined(HAVE_STRUCT_CMSGCRED) || defined(HAVE_STRUCT_FCRED) || \
 483          (defined(HAVE_STRUCT_SOCKCRED) && defined(LOCAL_CREDS)))
 484                         if (port->raddr.addr.ss_family == AF_UNIX)
 485                         {
 486 #if defined(HAVE_STRUCT_FCRED) || defined(HAVE_STRUCT_SOCKCRED)
 487
 488                                 /*
 489                                  * Receive credentials on next message receipt, BSD/OS,
 490                                  * NetBSD. We need to set this before the client sends the
 491                                  * next packet.
 492                                  */
 493                                 int                     on = 1;
 494
 495                                 if (setsockopt(port->sock, 0, LOCAL_CREDS, &on, sizeof(on)) < 0)
 496                                         ereport(FATAL,
 497                                                         (errcode_for_socket_access(),
 498                                         errmsg("could not enable credential reception: %m")));
 499 #endif
 500
 501                                 sendAuthRequest(port, AUTH_REQ_SCM_CREDS);
 502                         }
 503 #endif
 504                         status = authident(port);
 505                         break;
 506
 507                 case uaMD5:
 508                         sendAuthRequest(port, AUTH_REQ_MD5);
 509                         status = recv_and_check_password_packet(port);
 510                         break;
 511
 512                 case uaCrypt:
 513                         sendAuthRequest(port, AUTH_REQ_CRYPT);
 514                         status = recv_and_check_password_packet(port);
 515                         break;
 516
 517                 case uaPassword:
 518                         sendAuthRequest(port, AUTH_REQ_PASSWORD);
 519                         status = recv_and_check_password_packet(port);
 520                         break;
 521
 522 #ifdef USE_PAM
 523                 case uaPAM:
 524                         pam_port_cludge = port;
 525                         status = CheckPAMAuth(port, port->user_name, "");
 526                         break;
 527 #endif   /* USE_PAM */
 528
 529                 case uaTrust:
 530                         status = STATUS_OK;
 531                         break;
 532         }
 533
 534         if (status == STATUS_OK)
 535                 sendAuthRequest(port, AUTH_REQ_OK);
 536         else
 537                 auth_failed(port, status);
 538 }
 539
 540
 541 /*
 542  * Send an authentication request packet to the frontend.
 543  */
 544 static void
 545 sendAuthRequest(Port *port, AuthRequest areq)
 546 {
 547         StringInfoData buf;
 548
 549         pq_beginmessage(&buf, 'R');
 550         pq_sendint(&buf, (int32) areq, sizeof(int32));
 551
 552         /* Add the salt for encrypted passwords. */
 553         if (areq == AUTH_REQ_MD5)
 554                 pq_sendbytes(&buf, port->md5Salt, 4);
 555         else if (areq == AUTH_REQ_CRYPT)
 556                 pq_sendbytes(&buf, port->cryptSalt, 2);
 557
 558         pq_endmessage(&buf);
 559
 560         /*
 561          * Flush message so client will see it, except for AUTH_REQ_OK, which
 562          * need not be sent until we are ready for queries.
 563          */
 564         if (areq != AUTH_REQ_OK)
 565                 pq_flush();
 566 }
 567
 568
 569 #ifdef USE_PAM
 570
 571 /*
 572  * PAM conversation function
 573  */
 574
 575 static int
 576 pam_passwd_conv_proc(int num_msg, const struct pam_message ** msg,
 577                                          struct pam_response ** resp, void *appdata_ptr)
 578 {
 579         if (num_msg != 1 || msg[0]->msg_style != PAM_PROMPT_ECHO_OFF)
 580         {
 581                 switch (msg[0]->msg_style)
 582                 {
 583                         case PAM_ERROR_MSG:
 584                                 ereport(LOG,
 585                                                 (errmsg("error from underlying PAM layer: %s",
 586                                                                 msg[0]->msg)));
 587                                 return PAM_CONV_ERR;
 588                         default:
 589                                 ereport(LOG,
 590                                                 (errmsg("unsupported PAM conversation %d/%s",
 591                                                                 msg[0]->msg_style, msg[0]->msg)));
 592                                 return PAM_CONV_ERR;
 593                 }
 594         }
 595
 596         if (!appdata_ptr)
 597         {
 598                 /*
 599                  * Workaround for Solaris 2.6 where the PAM library is broken and
 600                  * does not pass appdata_ptr to the conversation routine
 601                  */
 602                 appdata_ptr = pam_passwd;
 603         }
 604
 605         /*
 606          * Password wasn't passed to PAM the first time around - let's go ask
 607          * the client to send a password, which we then stuff into PAM.
 608          */
 609         if (strlen(appdata_ptr) == 0)
 610         {
 611                 char       *passwd;
 612
 613                 sendAuthRequest(pam_port_cludge, AUTH_REQ_PASSWORD);
 614                 passwd = recv_password_packet(pam_port_cludge);
 615
 616                 if (passwd == NULL)
 617                         return PAM_CONV_ERR;    /* client didn't want to send password */
 618
 619                 if (strlen(passwd) == 0)
 620                 {
 621                         ereport(LOG,
 622                                         (errmsg("empty password returned by client")));
 623                         return PAM_CONV_ERR;
 624                 }
 625                 appdata_ptr = passwd;
 626         }
 627
 628         /*
 629          * Explicitly not using palloc here - PAM will free this memory in
 630          * pam_end()
 631          */
 632         *resp = calloc(num_msg, sizeof(struct pam_response));
 633         if (!*resp)
 634         {
 635                 ereport(LOG,
 636                                 (errcode(ERRCODE_OUT_OF_MEMORY),
 637                                  errmsg("out of memory")));
 638                 return PAM_CONV_ERR;
 639         }
 640
 641         (*resp)[0].resp = strdup((char *) appdata_ptr);
 642         (*resp)[0].resp_retcode = 0;
 643
 644         return ((*resp)[0].resp ? PAM_SUCCESS : PAM_CONV_ERR);
 645 }
 646
 647
 648 /*
 649  * Check authentication against PAM.
 650  */
 651 static int
 652 CheckPAMAuth(Port *port, char *user, char *password)
 653 {
 654         int                     retval;
 655         pam_handle_t *pamh = NULL;
 656
 657         /*
 658          * Apparently, Solaris 2.6 is broken, and needs ugly static variable
 659          * workaround
 660          */
 661         pam_passwd = password;
 662
 663         /*
 664          * Set the application data portion of the conversation struct This is
 665          * later used inside the PAM conversation to pass the password to the
 666          * authentication module.
 667          */
 668         pam_passw_conv.appdata_ptr = (char *) password;         /* from password above,
 669                                                                                                                  * not allocated */
 670
 671         /* Optionally, one can set the service name in pg_hba.conf */
 672         if (port->auth_arg && port->auth_arg[0] != '\0')
 673                 retval = pam_start(port->auth_arg, "pgsql@",
 674                                                    &pam_passw_conv, &pamh);
 675         else
 676                 retval = pam_start(PGSQL_PAM_SERVICE, "pgsql@",
 677                                                    &pam_passw_conv, &pamh);
 678
 679         if (retval != PAM_SUCCESS)
 680         {
 681                 ereport(LOG,
 682                                 (errmsg("could not create PAM authenticator: %s",
 683                                                 pam_strerror(pamh, retval))));
 684                 pam_passwd = NULL;              /* Unset pam_passwd */
 685                 return STATUS_ERROR;
 686         }
 687
 688         retval = pam_set_item(pamh, PAM_USER, user);
 689
 690         if (retval != PAM_SUCCESS)
 691         {
 692                 ereport(LOG,
 693                                 (errmsg("pam_set_item(PAM_USER) failed: %s",
 694                                                 pam_strerror(pamh, retval))));
 695                 pam_passwd = NULL;              /* Unset pam_passwd */
 696                 return STATUS_ERROR;
 697         }
 698
 699         retval = pam_set_item(pamh, PAM_CONV, &pam_passw_conv);
 700
 701         if (retval != PAM_SUCCESS)
 702         {
 703                 ereport(LOG,
 704                                 (errmsg("pam_set_item(PAM_CONV) failed: %s",
 705                                                 pam_strerror(pamh, retval))));
 706                 pam_passwd = NULL;              /* Unset pam_passwd */
 707                 return STATUS_ERROR;
 708         }
 709
 710         retval = pam_authenticate(pamh, 0);
 711
 712         if (retval != PAM_SUCCESS)
 713         {
 714                 ereport(LOG,
 715                                 (errmsg("pam_authenticate failed: %s",
 716                                                 pam_strerror(pamh, retval))));
 717                 pam_passwd = NULL;              /* Unset pam_passwd */
 718                 return STATUS_ERROR;
 719         }
 720
 721         retval = pam_acct_mgmt(pamh, 0);
 722
 723         if (retval != PAM_SUCCESS)
 724         {
 725                 ereport(LOG,
 726                                 (errmsg("pam_acct_mgmt failed: %s",
 727                                                 pam_strerror(pamh, retval))));
 728                 pam_passwd = NULL;              /* Unset pam_passwd */
 729                 return STATUS_ERROR;
 730         }
 731
 732         retval = pam_end(pamh, retval);
 733
 734         if (retval != PAM_SUCCESS)
 735         {
 736                 ereport(LOG,
 737                                 (errmsg("could not release PAM authenticator: %s",
 738                                                 pam_strerror(pamh, retval))));
 739         }
 740
 741         pam_passwd = NULL;                      /* Unset pam_passwd */
 742
 743         return (retval == PAM_SUCCESS ? STATUS_OK : STATUS_ERROR);
 744 }
 745 #endif   /* USE_PAM */
 746
 747
 748 /*
 749  * Collect password response packet from frontend.
 750  *
 751  * Returns NULL if couldn't get password, else palloc'd string.
 752  */
 753 static char *
 754 recv_password_packet(Port *port)
 755 {
 756         StringInfoData buf;
 757
 758         if (PG_PROTOCOL_MAJOR(port->proto) >= 3)
 759         {
 760                 /* Expect 'p' message type */
 761                 int                     mtype;
 762
 763                 mtype = pq_getbyte();
 764                 if (mtype != 'p')
 765                 {
 766                         /*
 767                          * If the client just disconnects without offering a password,
 768                          * don't make a log entry.  This is legal per protocol spec
 769                          * and in fact commonly done by psql, so complaining just
 770                          * clutters the log.
 771                          */
 772                         if (mtype != EOF)
 773                                 ereport(COMMERROR,
 774                                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 775                                 errmsg("expected password response, got message type %d",
 776                                            mtype)));
 777                         return NULL;            /* EOF or bad message type */
 778                 }
 779         }
 780         else
 781         {
 782                 /* For pre-3.0 clients, avoid log entry if they just disconnect */
 783                 if (pq_peekbyte() == EOF)
 784                         return NULL;            /* EOF */
 785         }
 786
 787         initStringInfo(&buf);
 788         if (pq_getmessage(&buf, 1000))          /* receive password */
 789         {
 790                 /* EOF - pq_getmessage already logged a suitable message */
 791                 pfree(buf.data);
 792                 return NULL;
 793         }
 794
 795         /*
 796          * Apply sanity check: password packet length should agree with length
 797          * of contained string.  Note it is safe to use strlen here because
 798          * StringInfo is guaranteed to have an appended '\0'.
 799          */
 800         if (strlen(buf.data) + 1 != buf.len)
 801                 ereport(COMMERROR,
 802                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 803                                  errmsg("invalid password packet size")));
 804
 805         /* Do not echo password to logs, for security. */
 806         ereport(DEBUG5,
 807                         (errmsg("received password packet")));
 808
 809         /*
 810          * Return the received string.  Note we do not attempt to do any
 811          * character-set conversion on it; since we don't yet know the
 812          * client's encoding, there wouldn't be much point.
 813          */
 814         return buf.data;
 815 }
 816
 817
 818 /*
 819  * Called when we have sent an authorization request for a password.
 820  * Get the response and check it.
 821  */
 822 static int
 823 recv_and_check_password_packet(Port *port)
 824 {
 825         char       *passwd;
 826         int                     result;
 827
 828         passwd = recv_password_packet(port);
 829
 830         if (passwd == NULL)
 831                 return STATUS_EOF;              /* client wouldn't send password */
 832
 833         result = md5_crypt_verify(port, port->user_name, passwd);
 834
 835         pfree(passwd);
 836
 837         return result;
 838 }