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Re: Compile error in current CVS, src/server.c:5500


From: Mark D. Baushke
Subject: Re: Compile error in current CVS, src/server.c:5500
Date: Mon, 21 Jul 2003 11:59:25 -0700

Derek Robert Price <address@hidden> writes:

> Brian Murphy wrote:
> 
> > Hi,
> >
> > Here is the fix. I didn't like the use of a fake error EACCES
> > in this situation, I prefer 0. EACCES refers to file access
> > failures not authentication / login failures as far as I'm aware.
> 
> 
> What, exactly, is wrong with calling pam_strerror() to get an error
> message from PAM for pam_end() errors and printing that, as Mark
> mentioned?

It seems that pam_strerror() has the first argument that is expected to
be a pointer to a pam_handle_t and there is concern about what happens
if pam_strerror() is called with an invalid pam_handle_t. So, if the
handle has already been destroyed, should it still be possible to use
pam_strerror() or not? I *thought* it should be, but I have not played
with it.

The FreeBSD implementation appears to deal with NULL being passed as the
pam_handle_t for purposes of getting errnum returned properly, but there
is some odd glue for UGLY_HACK_FOR_PRIOR_BEHAVIOR_SUPPORT wherein not
having a valid pam_handle_t might cause some more problems. So, it is
possible that not all implementations of pam will be as friendly.

I suppose another configure test could determine if it works or not...

At the very least, the return value of the pam_end() function call
should be captured and returned as an integer on the error string.

I would find it acceptable to use "error 0 ..." rather than the "error
EACCESS" I provided as a suggestion previously. I am not trying to force
thru how the PAM code is implemented. I just want it to be possible for
it to be supported when bugs are reported from the field.

> For that matter, why isn't this being done for returns
> other than PAM_SUCCESS in the preceding calls to pam_start(),
> pam_authenticate(), and pam_acct_mgmt()?

Good point. Those really should be handled as well.

As an FYI, here is the pam_strerror.c source code I have on a FreeBSD 4.x
system... I am sure that there are other implementations out there. 

I would hope it would be possible to turn the error numbers returned out
of the pam library into meaningful text. Otherwise, assertions that PAM
is a reasonable and mature API would seem to me to be a bit of a joke.

        Enjoy!
        -- Mark

         ------- FreeBSD contrib/libpam/pam_strerror.c -------
/* pam_strerror.c */

/* pam_strerror.c,v 1.1.1.1 1998/07/09 22:10:22 jdp Exp
 *
 * pam_strerror.c,v
 * Revision 1.1.1.1  1998/07/09 22:10:22  jdp
 * Virgin import of Linux-PAM-0.65, slightly stripped down.
 *
 * Revision 1.6  1997/01/04 20:12:02  morgan
 * replaced conditional FAIL_NOW with ABORT
 *
 * Revision 1.5  1996/07/07 23:58:56  morgan
 * corrected "... " to "..."
 *
 * Revision 1.4  1996/06/02 08:03:29  morgan
 * spelling correction
 *
 * Revision 1.3  1996/03/16 23:08:54  morgan
 * PAM --> Linux-PAM ;)
 *
 */

#include "pam_private.h"

const char *pam_strerror(pam_handle_t *pamh, int errnum)
{
#ifdef UGLY_HACK_FOR_PRIOR_BEHAVIOR_SUPPORT  /* will be removed from v 1.0 */

    int possible_error;

    possible_error = (int) pamh;
    if (!(possible_error >= 0 && possible_error <= PAM_BAD_ITEM)) {
        possible_error = errnum;
    }

/* mask standard behavior to use possible_error variable. */
#define errnum possible_error

#endif /* UGLY_HACK_FOR_PRIOR_BEHAVIOR_SUPPORT */

    switch (errnum) {
    case PAM_SUCCESS:
        return "Success";
    case PAM_ABORT:
        return "Critical error - immediate abort";
    case PAM_OPEN_ERR:
        return "dlopen() failure";
    case PAM_SYMBOL_ERR:
        return "Symbol not found";
    case PAM_SERVICE_ERR:
        return "Error in service module";
    case PAM_SYSTEM_ERR:
        return "System error";
    case PAM_BUF_ERR:
        return "Memory buffer error";
    case PAM_PERM_DENIED:
        return "Permission denied";
    case PAM_AUTH_ERR:
        return "Authentication failure";
    case PAM_CRED_INSUFFICIENT:
        return "Insufficient credentials to access authentication data";
    case PAM_AUTHINFO_UNAVAIL:
        return "Authentication service cannot retrieve authentication info.";
    case PAM_USER_UNKNOWN:
        return "User not known to the underlying authentication module";
    case PAM_MAXTRIES:
        return "Have exhasted maximum number of retries for service.";
    case PAM_NEW_AUTHTOK_REQD:
        return "Authentication token is no longer valid; new one required.";
    case PAM_ACCT_EXPIRED:
        return "User account has expired";
    case PAM_SESSION_ERR:
        return "Cannot make/remove an entry for the specified session";
    case PAM_CRED_UNAVAIL:
        return "Authentication service cannot retrieve user credentials";
    case PAM_CRED_EXPIRED:
        return "User credentials expired";
    case PAM_CRED_ERR:
        return "Failure setting user credentials";
    case PAM_NO_MODULE_DATA:
        return "No module specific data is present";
    case PAM_BAD_ITEM:
        return "Bad item passed to pam_*_item()";
    case PAM_CONV_ERR:
        return "Conversation error";
    case PAM_AUTHTOK_ERR:
        return "Authentication token manipulation error";
    case PAM_AUTHTOK_RECOVER_ERR:
        return "Authentication information cannot be recovered";
    case PAM_AUTHTOK_LOCK_BUSY:
        return "Authentication token lock busy";
    case PAM_AUTHTOK_DISABLE_AGING:
        return "Authentication token aging disabled";
    case PAM_TRY_AGAIN:
        return "Failed preliminary check by password service";
    case PAM_IGNORE:
        return "Please ignore underlying account module";
    case PAM_MODULE_UNKNOWN:
        return "Module is unknown";
    case PAM_AUTHTOK_EXPIRED:
        return "Authentication token expired";
    case PAM_CONV_AGAIN:
        return "Conversation is waiting for event";
    case PAM_INCOMPLETE:
        return "Application needs to call libpam again";
    }

    return "Unknown Linux-PAM error (need to upgrde libpam?)";
}




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