Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Description of problem:
We got a customer report of a command going through PAM crashing for a given user.
It appears that the pam_lastlog code doesn't check the result of localtime_r(), which leads to crashing in glibc's strftime():
~~~
494 static int
495 last_login_failed(pam_handle_t *pamh, int announce, const char *user, time_t lltime)
496 {
:
502 char the_time[256];
:
535 if (failed) {
536 /* we want the date? */
537 if (announce & LASTLOG_DATE) {
538 struct tm *tm, tm_buf;
539 time_t lf_time;
540
541 lf_time = utuser.ut_tv.tv_sec;
542 tm = localtime_r (&lf_time, &tm_buf);
543 strftime (the_time, sizeof (the_time),
544 /* TRANSLATORS: "strftime options for date of last login" */
545 _(" %a %b %e %H:%M:%S %Z %Y"), tm);
546
547 date = the_time;
548 }
~~~
Here above, assuming "lf_time" is very large, due to a corruption in btmp database, this leads to:
1. having "tm" = NULL
2. calling strftime(..., NULL), which crashes
Hence, checking the result is mandatory.
Version-Release number of selected component (if applicable):
PAM from RHEL7 and later
How reproducible:
Don't know, need to have a corrupted "btmp" entry
The customer gave me his btmp database but unfortunately I couldn't reproduce with it either: PAM was detecting the corruption for me, whereas not for the customer.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (pam bug fix and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2023:2954
Description of problem: We got a customer report of a command going through PAM crashing for a given user. It appears that the pam_lastlog code doesn't check the result of localtime_r(), which leads to crashing in glibc's strftime(): ~~~ 494 static int 495 last_login_failed(pam_handle_t *pamh, int announce, const char *user, time_t lltime) 496 { : 502 char the_time[256]; : 535 if (failed) { 536 /* we want the date? */ 537 if (announce & LASTLOG_DATE) { 538 struct tm *tm, tm_buf; 539 time_t lf_time; 540 541 lf_time = utuser.ut_tv.tv_sec; 542 tm = localtime_r (&lf_time, &tm_buf); 543 strftime (the_time, sizeof (the_time), 544 /* TRANSLATORS: "strftime options for date of last login" */ 545 _(" %a %b %e %H:%M:%S %Z %Y"), tm); 546 547 date = the_time; 548 } ~~~ Here above, assuming "lf_time" is very large, due to a corruption in btmp database, this leads to: 1. having "tm" = NULL 2. calling strftime(..., NULL), which crashes Hence, checking the result is mandatory. Version-Release number of selected component (if applicable): PAM from RHEL7 and later How reproducible: Don't know, need to have a corrupted "btmp" entry