src/backend/libpq/auth.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * auth.c
   4  *        Routines to handle network authentication
   5  *
   6  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/libpq/auth.c,v 1.109 2003/08/04 00:43:18 momjian 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("kerberos protocol version \"%s\" != \"%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("kerberos user name \"%s\" != \"%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 v4 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 init 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 resolve 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("kerberos user name \"%s\" != \"%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 v5 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 *authmethod = "Unknown auth method:";
 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                         authmethod = "Rejected host:";
 367                         break;
 368                 case uaKrb4:
 369                         authmethod = "Kerberos4";
 370                         break;
 371                 case uaKrb5:
 372                         authmethod = "Kerberos5";
 373                         break;
 374                 case uaTrust:
 375                         authmethod = "Trusted";
 376                         break;
 377                 case uaIdent:
 378                         authmethod = "IDENT";
 379                         break;
 380                 case uaMD5:
 381                 case uaCrypt:
 382                 case uaPassword:
 383                         authmethod = "Password";
 384                         break;
 385 #ifdef USE_PAM
 386                 case uaPAM:
 387                         authmethod = "PAM";
 388                         break;
 389 #endif   /* USE_PAM */
 390         }
 391
 392         ereport(FATAL,
 393                         (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 394                          errmsg("%s authentication failed for user \"%s\"",
 395                                         authmethod, port->user_name)));
 396         /* doesn't return */
 397 }
 398
 399
 400 /*
 401  * Client authentication starts here.  If there is an error, this
 402  * function does not return and the backend process is terminated.
 403  */
 404 void
 405 ClientAuthentication(Port *port)
 406 {
 407         int                     status = STATUS_ERROR;
 408
 409         /*
 410          * Get the authentication method to use for this frontend/database
 411          * combination.  Note: a failure return indicates a problem with the
 412          * hba config file, not with the request.  hba.c should have dropped
 413          * an error message into the postmaster logfile if it failed.
 414          */
 415         if (hba_getauthmethod(port) != STATUS_OK)
 416                 ereport(FATAL,
 417                                 (errcode(ERRCODE_CONFIG_FILE_ERROR),
 418                                  errmsg("missing or erroneous pg_hba.conf file"),
 419                                  errhint("See postmaster log for details.")));
 420
 421         switch (port->auth_method)
 422         {
 423                 case uaReject:
 424
 425                         /*
 426                          * This could have come from an explicit "reject" entry in
 427                          * pg_hba.conf, but more likely it means there was no matching
 428                          * entry.  Take pity on the poor user and issue a helpful
 429                          * error message.  NOTE: this is not a security breach,
 430                          * because all the info reported here is known at the frontend
 431                          * and must be assumed known to bad guys. We're merely helping
 432                          * out the less clueful good guys.
 433                          */
 434                         {
 435                                 char            hostinfo[NI_MAXHOST];
 436
 437                                 getnameinfo_all(&port->raddr.addr, port->raddr.salen,
 438                                                                 hostinfo, sizeof(hostinfo),
 439                                                                 NULL, 0,
 440                                                                 NI_NUMERICHOST);
 441
 442 #ifdef USE_SSL
 443                                 ereport(FATAL,
 444                                    (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 445                                         errmsg("no pg_hba.conf entry for host \"%s\", user \"%s\", database \"%s\", %s",
 446                                                    hostinfo, port->user_name, port->database_name,
 447                                    port->ssl ? gettext("SSL on") : gettext("SSL off"))));
 448 #else
 449                                 ereport(FATAL,
 450                                    (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
 451                                         errmsg("no pg_hba.conf entry for host \"%s\", user \"%s\", database \"%s\"",
 452                                            hostinfo, port->user_name, port->database_name)));
 453 #endif
 454                                 break;
 455                         }
 456
 457                 case uaKrb4:
 458                         /* Kerberos 4 only seems to work with AF_INET. */
 459                         if (port->raddr.addr.ss_family != AF_INET
 460                                 || port->laddr.addr.ss_family != AF_INET)
 461                                 ereport(FATAL,
 462                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 463                                    errmsg("kerberos 4 only supports IPv4 connections")));
 464                         sendAuthRequest(port, AUTH_REQ_KRB4);
 465                         status = pg_krb4_recvauth(port);
 466                         break;
 467
 468                 case uaKrb5:
 469                         sendAuthRequest(port, AUTH_REQ_KRB5);
 470                         status = pg_krb5_recvauth(port);
 471                         break;
 472
 473                 case uaIdent:
 474 #if defined(HAVE_STRUCT_CMSGCRED) || defined(HAVE_STRUCT_FCRED) || \
 475         (defined(HAVE_STRUCT_SOCKCRED) && defined(LOCAL_CREDS)) && \
 476         !defined(HAVE_GETPEEREID) && !defined(SO_PEERCRED)
 477
 478                         /*
 479                          * If we are doing ident on unix-domain sockets, use SCM_CREDS
 480                          * only if it is defined and SO_PEERCRED isn't.
 481                          */
 482 #if defined(HAVE_STRUCT_FCRED) || defined(HAVE_STRUCT_SOCKCRED)
 483
 484                         /*
 485                          * Receive credentials on next message receipt, BSD/OS,
 486                          * NetBSD. We need to set this before the client sends the
 487                          * next packet.
 488                          */
 489                         {
 490                                 int                     on = 1;
 491
 492                                 if (setsockopt(port->sock, 0, LOCAL_CREDS, &on, sizeof(on)) < 0)
 493                                         ereport(FATAL,
 494                                                         (errcode_for_socket_access(),
 495                                          errmsg("failed to enable credential receipt: %m")));
 496                         }
 497 #endif
 498                         if (port->raddr.addr.ss_family == AF_UNIX)
 499                                 sendAuthRequest(port, AUTH_REQ_SCM_CREDS);
 500 #endif
 501                         status = authident(port);
 502                         break;
 503
 504                 case uaMD5:
 505                         sendAuthRequest(port, AUTH_REQ_MD5);
 506                         status = recv_and_check_password_packet(port);
 507                         break;
 508
 509                 case uaCrypt:
 510                         sendAuthRequest(port, AUTH_REQ_CRYPT);
 511                         status = recv_and_check_password_packet(port);
 512                         break;
 513
 514                 case uaPassword:
 515                         sendAuthRequest(port, AUTH_REQ_PASSWORD);
 516                         status = recv_and_check_password_packet(port);
 517                         break;
 518
 519 #ifdef USE_PAM
 520                 case uaPAM:
 521                         pam_port_cludge = port;
 522                         status = CheckPAMAuth(port, port->user_name, "");
 523                         break;
 524 #endif   /* USE_PAM */
 525
 526                 case uaTrust:
 527                         status = STATUS_OK;
 528                         break;
 529         }
 530
 531         if (status == STATUS_OK)
 532                 sendAuthRequest(port, AUTH_REQ_OK);
 533         else
 534                 auth_failed(port, status);
 535 }
 536
 537
 538 /*
 539  * Send an authentication request packet to the frontend.
 540  */
 541 static void
 542 sendAuthRequest(Port *port, AuthRequest areq)
 543 {
 544         StringInfoData buf;
 545
 546         pq_beginmessage(&buf, 'R');
 547         pq_sendint(&buf, (int32) areq, sizeof(int32));
 548
 549         /* Add the salt for encrypted passwords. */
 550         if (areq == AUTH_REQ_MD5)
 551                 pq_sendbytes(&buf, port->md5Salt, 4);
 552         else if (areq == AUTH_REQ_CRYPT)
 553                 pq_sendbytes(&buf, port->cryptSalt, 2);
 554
 555         pq_endmessage(&buf);
 556
 557         /*
 558          * Flush message so client will see it, except for AUTH_REQ_OK, which
 559          * need not be sent until we are ready for queries.
 560          */
 561         if (areq != AUTH_REQ_OK)
 562                 pq_flush();
 563 }
 564
 565
 566 #ifdef USE_PAM
 567
 568 /*
 569  * PAM conversation function
 570  */
 571
 572 static int
 573 pam_passwd_conv_proc(int num_msg, const struct pam_message ** msg,
 574                                          struct pam_response ** resp, void *appdata_ptr)
 575 {
 576         if (num_msg != 1 || msg[0]->msg_style != PAM_PROMPT_ECHO_OFF)
 577         {
 578                 switch (msg[0]->msg_style)
 579                 {
 580                         case PAM_ERROR_MSG:
 581                                 ereport(LOG,
 582                                                 (errmsg("error from underlying PAM layer: %s",
 583                                                                 msg[0]->msg)));
 584                                 return PAM_CONV_ERR;
 585                         default:
 586                                 ereport(LOG,
 587                                                 (errmsg("unsupported PAM conversation %d/%s",
 588                                                                 msg[0]->msg_style, msg[0]->msg)));
 589                                 return PAM_CONV_ERR;
 590                 }
 591         }
 592
 593         if (!appdata_ptr)
 594         {
 595                 /*
 596                  * Workaround for Solaris 2.6 where the PAM library is broken and
 597                  * does not pass appdata_ptr to the conversation routine
 598                  */
 599                 appdata_ptr = pam_passwd;
 600         }
 601
 602         /*
 603          * Password wasn't passed to PAM the first time around - let's go ask
 604          * the client to send a password, which we then stuff into PAM.
 605          */
 606         if (strlen(appdata_ptr) == 0)
 607         {
 608                 char       *passwd;
 609
 610                 sendAuthRequest(pam_port_cludge, AUTH_REQ_PASSWORD);
 611                 passwd = recv_password_packet(pam_port_cludge);
 612
 613                 if (passwd == NULL)
 614                         return PAM_CONV_ERR;    /* client didn't want to send password */
 615
 616                 if (strlen(passwd) == 0)
 617                 {
 618                         ereport(LOG,
 619                                         (errmsg("empty password returned by client")));
 620                         return PAM_CONV_ERR;
 621                 }
 622                 appdata_ptr = passwd;
 623         }
 624
 625         /*
 626          * Explicitly not using palloc here - PAM will free this memory in
 627          * pam_end()
 628          */
 629         *resp = calloc(num_msg, sizeof(struct pam_response));
 630         if (!*resp)
 631         {
 632                 ereport(LOG,
 633                                 (errcode(ERRCODE_OUT_OF_MEMORY),
 634                                  errmsg("out of memory")));
 635                 return PAM_CONV_ERR;
 636         }
 637
 638         (*resp)[0].resp = strdup((char *) appdata_ptr);
 639         (*resp)[0].resp_retcode = 0;
 640
 641         return ((*resp)[0].resp ? PAM_SUCCESS : PAM_CONV_ERR);
 642 }
 643
 644
 645 /*
 646  * Check authentication against PAM.
 647  */
 648 static int
 649 CheckPAMAuth(Port *port, char *user, char *password)
 650 {
 651         int                     retval;
 652         pam_handle_t *pamh = NULL;
 653
 654         /*
 655          * Apparently, Solaris 2.6 is broken, and needs ugly static variable
 656          * workaround
 657          */
 658         pam_passwd = password;
 659
 660         /*
 661          * Set the application data portion of the conversation struct This is
 662          * later used inside the PAM conversation to pass the password to the
 663          * authentication module.
 664          */
 665         pam_passw_conv.appdata_ptr = (char *) password;         /* from password above,
 666                                                                                                                  * not allocated */
 667
 668         /* Optionally, one can set the service name in pg_hba.conf */
 669         if (port->auth_arg && port->auth_arg[0] != '\0')
 670                 retval = pam_start(port->auth_arg, "pgsql@",
 671                                                    &pam_passw_conv, &pamh);
 672         else
 673                 retval = pam_start(PGSQL_PAM_SERVICE, "pgsql@",
 674                                                    &pam_passw_conv, &pamh);
 675
 676         if (retval != PAM_SUCCESS)
 677         {
 678                 ereport(LOG,
 679                                 (errmsg("Failed to create PAM authenticator: %s",
 680                                                 pam_strerror(pamh, retval))));
 681                 pam_passwd = NULL;              /* Unset pam_passwd */
 682                 return STATUS_ERROR;
 683         }
 684
 685         retval = pam_set_item(pamh, PAM_USER, user);
 686
 687         if (retval != PAM_SUCCESS)
 688         {
 689                 ereport(LOG,
 690                                 (errmsg("pam_set_item(PAM_USER) failed: %s",
 691                                                 pam_strerror(pamh, retval))));
 692                 pam_passwd = NULL;              /* Unset pam_passwd */
 693                 return STATUS_ERROR;
 694         }
 695
 696         retval = pam_set_item(pamh, PAM_CONV, &pam_passw_conv);
 697
 698         if (retval != PAM_SUCCESS)
 699         {
 700                 ereport(LOG,
 701                                 (errmsg("pam_set_item(PAM_CONV) failed: %s",
 702                                                 pam_strerror(pamh, retval))));
 703                 pam_passwd = NULL;              /* Unset pam_passwd */
 704                 return STATUS_ERROR;
 705         }
 706
 707         retval = pam_authenticate(pamh, 0);
 708
 709         if (retval != PAM_SUCCESS)
 710         {
 711                 ereport(LOG,
 712                                 (errmsg("pam_authenticate failed: %s",
 713                                                 pam_strerror(pamh, retval))));
 714                 pam_passwd = NULL;              /* Unset pam_passwd */
 715                 return STATUS_ERROR;
 716         }
 717
 718         retval = pam_acct_mgmt(pamh, 0);
 719
 720         if (retval != PAM_SUCCESS)
 721         {
 722                 ereport(LOG,
 723                                 (errmsg("pam_acct_mgmt failed: %s",
 724                                                 pam_strerror(pamh, retval))));
 725                 pam_passwd = NULL;              /* Unset pam_passwd */
 726                 return STATUS_ERROR;
 727         }
 728
 729         retval = pam_end(pamh, retval);
 730
 731         if (retval != PAM_SUCCESS)
 732         {
 733                 ereport(LOG,
 734                                 (errmsg("failed to release PAM authenticator: %s",
 735                                                 pam_strerror(pamh, retval))));
 736         }
 737
 738         pam_passwd = NULL;                      /* Unset pam_passwd */
 739
 740         return (retval == PAM_SUCCESS ? STATUS_OK : STATUS_ERROR);
 741 }
 742 #endif   /* USE_PAM */
 743
 744
 745 /*
 746  * Collect password response packet from frontend.
 747  *
 748  * Returns NULL if couldn't get password, else palloc'd string.
 749  */
 750 static char *
 751 recv_password_packet(Port *port)
 752 {
 753         StringInfoData buf;
 754
 755         if (PG_PROTOCOL_MAJOR(port->proto) >= 3)
 756         {
 757                 /* Expect 'p' message type */
 758                 int                     mtype;
 759
 760                 mtype = pq_getbyte();
 761                 if (mtype != 'p')
 762                 {
 763                         /*
 764                          * If the client just disconnects without offering a password,
 765                          * don't make a log entry.  This is legal per protocol spec
 766                          * and in fact commonly done by psql, so complaining just
 767                          * clutters the log.
 768                          */
 769                         if (mtype != EOF)
 770                                 ereport(COMMERROR,
 771                                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 772                                         errmsg("expected password response, got msg type %d",
 773                                                    mtype)));
 774                         return NULL;            /* EOF or bad message type */
 775                 }
 776         }
 777         else
 778         {
 779                 /* For pre-3.0 clients, avoid log entry if they just disconnect */
 780                 if (pq_peekbyte() == EOF)
 781                         return NULL;            /* EOF */
 782         }
 783
 784         initStringInfo(&buf);
 785         if (pq_getmessage(&buf, 1000))          /* receive password */
 786         {
 787                 /* EOF - pq_getmessage already logged a suitable message */
 788                 pfree(buf.data);
 789                 return NULL;
 790         }
 791
 792         /*
 793          * Apply sanity check: password packet length should agree with length
 794          * of contained string.  Note it is safe to use strlen here because
 795          * StringInfo is guaranteed to have an appended '\0'.
 796          */
 797         if (strlen(buf.data) + 1 != buf.len)
 798                 ereport(COMMERROR,
 799                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 800                                  errmsg("invalid password packet size")));
 801
 802         /* Do not echo password to logs, for security. */
 803         ereport(DEBUG5,
 804                         (errmsg("received password packet")));
 805
 806         /*
 807          * Return the received string.  Note we do not attempt to do any
 808          * character-set conversion on it; since we don't yet know the
 809          * client's encoding, there wouldn't be much point.
 810          */
 811         return buf.data;
 812 }
 813
 814
 815 /*
 816  * Called when we have sent an authorization request for a password.
 817  * Get the response and check it.
 818  */
 819 static int
 820 recv_and_check_password_packet(Port *port)
 821 {
 822         char       *passwd;
 823         int                     result;
 824
 825         passwd = recv_password_packet(port);
 826
 827         if (passwd == NULL)
 828                 return STATUS_EOF;              /* client wouldn't send password */
 829
 830         result = md5_crypt_verify(port, port->user_name, passwd);
 831
 832         pfree(passwd);
 833
 834         return result;
 835 }