Re: [HACKERS] User authentication bug?

Maarten Boekhold <maartenb(at)dutepp2(dot)et(dot)tudelft(dot)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 ----