From 80dc2d410595b5193d32f965185710df27f3984e Mon Sep 17 00:00:00 2001
From: Md Zain Hasib <hasibm@vmware.com>
Date: Sat, 29 Jul 2023 11:01:35 +0530
Subject: [PATCH] pam_pwhistory: fix passing NULL filename argument to
 pwhistory helper

This change fixes a bug when pwhistory_helper is invoked from
pam_pwhistory with an NULL filename, pwhistory_helper receives a short
circuited argc count of 3, ignoring the rest of the arguments passed
due to filename being NULL. To resolve the issue, an empty string is
passed in case the filename is empty, which is later changed back to
NULL in pwhistory_helper so that it can be passed to opasswd to read
the default opasswd file.

* modules/pam_pwhistory/pam_pwhistory.c (run_save_helper,
run_check_helper): Replace NULL filename argument with an empty string.
* modules/pam_pwhistory/pwhistory_helper.c (main): Replace empty string
filename argument with NULL.

Fixes: 11c35109a67f ("pam_pwhistory: Enable alternate location for password history file (#396)")
Signed-off-by: Dmitry V. Levin <ldv@strace.io>

Reference: https://github.com/linux-pam/linux-pam/commit/80dc2d410595b5193d32f965185710df27f3984e
Conflict: NA
---
 modules/pam_pwhistory/pam_pwhistory.c    | 4 ++--
 modules/pam_pwhistory/pwhistory_helper.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/modules/pam_pwhistory/pam_pwhistory.c b/modules/pam_pwhistory/pam_pwhistory.c
index 5a7fb81..98ddffc 100644
--- a/modules/pam_pwhistory/pam_pwhistory.c
+++ b/modules/pam_pwhistory/pam_pwhistory.c
@@ -141,7 +141,7 @@ run_save_helper(pam_handle_t *pamh, const char *user,
       args[0] = (char *)PWHISTORY_HELPER;
       args[1] = (char *)"save";
       args[2] = (char *)user;
-      args[3] = (char *)filename;
+      args[3] = (char *)((filename != NULL) ? filename : "");
       DIAG_POP_IGNORE_CAST_QUAL;
       if (asprintf(&args[4], "%d", howmany) < 0 ||
           asprintf(&args[5], "%d", debug) < 0)
@@ -228,7 +228,7 @@ run_check_helper(pam_handle_t *pamh, const char *user,
       args[0] = (char *)PWHISTORY_HELPER;
       args[1] = (char *)"check";
       args[2] = (char *)user;
-      args[3] = (char *)filename;
+      args[3] = (char *)((filename != NULL) ? filename : "");
       DIAG_POP_IGNORE_CAST_QUAL;
       if (asprintf(&args[4], "%d", debug) < 0)
         {
diff --git a/modules/pam_pwhistory/pwhistory_helper.c b/modules/pam_pwhistory/pwhistory_helper.c
index 469d95f..fb9a1e3 100644
--- a/modules/pam_pwhistory/pwhistory_helper.c
+++ b/modules/pam_pwhistory/pwhistory_helper.c
@@ -108,7 +108,7 @@ main(int argc, char *argv[])
 
   option = argv[1];
   user = argv[2];
-  filename = argv[3];
+  filename = (argv[3][0] != '\0') ? argv[3] : NULL;
 
   if (strcmp(option, "check") == 0 && argc == 5)
     return check_history(user, filename, argv[4]);
-- 
2.43.0