Re: [HACKERS] User authentication bug? - Mailing list pgsql-hackers

Maarten Boekhold <maartenb@dutepp2.et.tudelft.nl> writes:
> OK, I now know what's going on, at least at my home (I had this problem
> on another server, dunno if it's caused by the same thing):
>     I had a password longer than 8 characters in pg_shadow.
> when creating a user, postgres happily accepts more than 8 chars, and
> also stores them. apparently libpq-fe (or psql, dunno) only sends 8
> chars.

It's not libpq's fault (at least not with the current sources).
It's psql's.  psql.c had a hardwired limit of 8 characters on
both the username and the password.  Ick.

With the attached patch, I have verified that long (> 8char anyway)
usernames and passwords work correctly in both "password" and "crypt"
authorization mode.  NOTE: at least on my machine, it seems that the
crypt() routines ignore the part of the password beyond 8 characters,
so there's no security gain from longer passwords in crypt auth mode.
But they don't fail.

The login-related part of psql has apparently not been touched since
roughly the fall of Rome ;-).  It was going through huge pushups to
get around the lack of username/login parameters to PQsetdb.  I don't
know when PQsetdbLogin was added to libpq, but it's there now ... so
I was able to rip out quite a lot of crufty code while I was at it.

It's possible that there are still bogus length limits on username
or password in some of the other PostgreSQL user interfaces besides
psql/libpq.  I will leave it to other folks to check that code.

            regards, tom lane


*** src/bin/psql/psql.c.orig    Sat Jul 18 14:34:14 1998
--- src/bin/psql/psql.c    Sat Aug  1 20:34:47 1998
***************
*** 132,140 ****
  static int    objectDescription(PsqlSettings *pset, char *object);
  static int    rightsList(PsqlSettings *pset);
  static void prompt_for_password(char *username, char *password);
- static char *
- make_connect_string(char *host, char *port, char *dbname,
-                     char *username, char *password);

  static char *gets_noreadline(char *prompt, FILE *source);
  static char *gets_readline(char *prompt, FILE *source);
--- 132,137 ----
***************
*** 1372,1406 ****
      else
      {
          PGconn       *olddb = pset->db;
-         static char *userenv = NULL;
-         char       *old_userenv = NULL;
          const char *dbparam;
!
!         if (new_user != NULL)
!         {
!
!             /*
!              * PQsetdb() does not allow us to specify the user, so we have
!              * to do it via PGUSER
!              */
!             if (userenv != NULL)
!                 old_userenv = userenv;
!             userenv = malloc(strlen("PGUSER=") + strlen(new_user) + 1);
!             sprintf(userenv, "PGUSER=%s", new_user);
!             /* putenv() may continue to use memory as part of environment */
!             putenv(userenv);
!             /* can delete old memory if we malloc'ed it */
!             if (old_userenv != NULL)
!                 free(old_userenv);
!         }

          if (strcmp(new_dbname, "-") != 0)
              dbparam = new_dbname;
          else
              dbparam = PQdb(olddb);

!         pset->db = PQsetdb(PQhost(olddb), PQport(olddb),
!                            NULL, NULL, dbparam);
          if (!pset->quiet)
          {
              if (!new_user)
--- 1369,1396 ----
      else
      {
          PGconn       *olddb = pset->db;
          const char *dbparam;
!         const char *userparam;
!         const char *pwparam;

          if (strcmp(new_dbname, "-") != 0)
              dbparam = new_dbname;
          else
              dbparam = PQdb(olddb);

!         if (new_user != NULL && strcmp(new_user, "-") != 0)
!             userparam = new_user;
!         else
!             userparam = PQuser(olddb);
!
!         /* libpq doesn't provide an accessor function for the password,
!          * so we cheat here.
!          */
!         pwparam = olddb->pgpass;
!
!         pset->db = PQsetdbLogin(PQhost(olddb), PQport(olddb),
!                                 NULL, NULL, dbparam, userparam, pwparam);
!
          if (!pset->quiet)
          {
              if (!new_user)
***************
*** 2711,2726 ****

      if (settings.getPassword)
      {
!         char        username[9];
!         char        password[9];
!         char       *connect_string;

          prompt_for_password(username, password);

!         /* now use PQconnectdb so we can pass these options */
!         connect_string = make_connect_string(host, port, dbname, username, password);
!         settings.db = PQconnectdb(connect_string);
!         free(connect_string);
      }
      else
          settings.db = PQsetdb(host, port, NULL, NULL, dbname);
--- 2701,2713 ----

      if (settings.getPassword)
      {
!         char        username[100];
!         char        password[100];

          prompt_for_password(username, password);

!         settings.db = PQsetdbLogin(host, port, NULL, NULL, dbname,
!                                    username, password);
      }
      else
          settings.db = PQsetdb(host, port, NULL, NULL, dbname);
***************
*** 2730,2736 ****
      if (PQstatus(settings.db) == CONNECTION_BAD)
      {
          fprintf(stderr, "Connection to database '%s' failed.\n", dbname);
!         fprintf(stderr, "%s", PQerrorMessage(settings.db));
          PQfinish(settings.db);
          exit(1);
      }
--- 2717,2723 ----
      if (PQstatus(settings.db) == CONNECTION_BAD)
      {
          fprintf(stderr, "Connection to database '%s' failed.\n", dbname);
!         fprintf(stderr, "%s\n", PQerrorMessage(settings.db));
          PQfinish(settings.db);
          exit(1);
      }
***************
*** 2964,2969 ****
--- 2951,2957 ----
  static void
  prompt_for_password(char *username, char *password)
  {
+     char buf[512];
      int            length;

  #ifdef HAVE_TERMIOS_H
***************
*** 2973,2985 ****
  #endif

      printf("Username: ");
!     fgets(username, 9, stdin);
      length = strlen(username);
      /* skip rest of the line */
      if (length > 0 && username[length - 1] != '\n')
      {
-         static char buf[512];
-
          do
          {
              fgets(buf, 512, stdin);
--- 2961,2971 ----
  #endif

      printf("Username: ");
!     fgets(username, 100, stdin);
      length = strlen(username);
      /* skip rest of the line */
      if (length > 0 && username[length - 1] != '\n')
      {
          do
          {
              fgets(buf, 512, stdin);
***************
*** 2995,3001 ****
      t.c_lflag &= ~ECHO;
      tcsetattr(0, TCSADRAIN, &t);
  #endif
!     fgets(password, 9, stdin);
  #ifdef HAVE_TERMIOS_H
      tcsetattr(0, TCSADRAIN, &t_orig);
  #endif
--- 2981,2987 ----
      t.c_lflag &= ~ECHO;
      tcsetattr(0, TCSADRAIN, &t);
  #endif
!     fgets(password, 100, stdin);
  #ifdef HAVE_TERMIOS_H
      tcsetattr(0, TCSADRAIN, &t_orig);
  #endif
***************
*** 3004,3011 ****
      /* skip rest of the line */
      if (length > 0 && password[length - 1] != '\n')
      {
-         static char buf[512];
-
          do
          {
              fgets(buf, 512, stdin);
--- 2990,2995 ----
***************
*** 3015,3077 ****
          password[length - 1] = '\0';

      printf("\n\n");
- }
-
- static char *
- make_connect_string(char *host, char *port, char *dbname,
-                     char *username, char *password)
- {
-     int            connect_string_len = 0;
-     char       *connect_string;
-
-     if (host)
-         connect_string_len += 6 + strlen(host); /* 6 == "host=" + " " */
-     if (username)
-         connect_string_len += 6 + strlen(username);        /* 6 == "user=" + " " */
-     if (password)
-         connect_string_len += 10 + strlen(password);    /* 10 == "password=" + "
-                                                          * " */
-     if (port)
-         connect_string_len += 6 + strlen(port); /* 6 == "port=" + " " */
-     if (dbname)
-         connect_string_len += 8 + strlen(dbname);        /* 8 == "dbname=" + " " */
-     connect_string_len += 18;    /* "authtype=password" + null */
-
-     connect_string = (char *) malloc(connect_string_len);
-     if (!connect_string)
-         return 0;
-     connect_string[0] = '\0';
-     if (host)
-     {
-         strcat(connect_string, "host=");
-         strcat(connect_string, host);
-         strcat(connect_string, " ");
-     }
-     if (username)
-     {
-         strcat(connect_string, "user=");
-         strcat(connect_string, username);
-         strcat(connect_string, " ");
-     }
-     if (password)
-     {
-         strcat(connect_string, "password=");
-         strcat(connect_string, password);
-         strcat(connect_string, " ");
-     }
-     if (port)
-     {
-         strcat(connect_string, "port=");
-         strcat(connect_string, port);
-         strcat(connect_string, " ");
-     }
-     if (dbname)
-     {
-         strcat(connect_string, "dbname=");
-         strcat(connect_string, dbname);
-         strcat(connect_string, " ");
-     }
-     strcat(connect_string, "authtype=password");
-
-     return connect_string;
  }
--- 2999,3002 ----