diff -ur b/at.c a/at.c
--- b/at.c 2022-01-29 17:42:19.000000000 +0100
+++ a/at.c 2022-02-23 18:42:45.941757090 +0100
@@ -155,18 +155,12 @@
/* If the user presses ^C, remove the spool file and exit
*/
if (fcreated) {
- /*
PRIV_START
-
+ /*
We need the unprivileged uid here since the file is owned by the real
(not effective) uid.
*/
- setregid(real_gid, effective_gid);
- unlink(atfile);
- setregid(effective_gid, real_gid);
- /*
PRIV_END
- */
}
exit(EXIT_FAILURE);
}
@@ -326,26 +320,19 @@
* bit. Yes, this is a kluge.
*/
cmask = umask(S_IRUSR | S_IWUSR | S_IXUSR);
- seteuid(real_uid);
+ if ((seteuid(effective_uid)) < 0)
+ perr("Error in seteuid: %s", errno);
if ((fd = open(atfile, O_CREAT | O_EXCL | O_TRUNC | O_WRONLY | O_SYNC, S_IRUSR)) == -1)
perr("Cannot create atjob file %.500s", atfile);
- seteuid(effective_uid);
if ((fd2 = dup(fd)) < 0)
perr("Error in dup() of job file");
- /*
if (fchown(fd2, real_uid, real_gid) != 0)
- perr("Cannot give away file");
- */
+ perr("Cannot give real_uid and real_gid the file");
PRIV_END
- /* We no longer need suid root; now we just need to be able to write
- * to the directory, if necessary.
- */
-
- REDUCE_PRIV(daemon_uid, daemon_gid)
/* We've successfully created the file; let's set the flag so it
* gets removed in case of an interrupt or error.
*/
@@ -733,7 +720,7 @@
We need the unprivileged uid here since the file is owned by the real
(not effective) uid.
*/
- setregid(real_gid, effective_gid);
+ PRIV_START
if (queue == '=') {
fprintf(stderr, "Warning: deleting running job\n");
@@ -742,8 +729,8 @@
perr("Cannot unlink %.500s", dirent->d_name);
rc = EXIT_FAILURE;
}
+ PRIV_END
- setregid(effective_gid, real_gid);
done = 1;
break;
@@ -753,7 +740,7 @@
FILE *fp;
int ch;
- setregid(real_gid, effective_gid);
+ PRIV_START
fp = fopen(dirent->d_name, "r");
if (fp) {
@@ -768,7 +755,7 @@
perr("Cannot open %.500s", dirent->d_name);
rc = EXIT_FAILURE;
}
- setregid(effective_gid, real_gid);
+ PRIV_END
}
break;
diff -ur b/atd.c a/atd.c
--- b/atd.c 2022-01-29 17:42:19.000000000 +0100
+++ a/atd.c 2022-02-23 18:50:53.743511813 +0100
@@ -91,6 +91,10 @@
/* Macros */
+#ifndef LOG_ATD
+#define LOG_ATD LOG_DAEMON
+#endif
+
#define BATCH_INTERVAL_DEFAULT 60
#define CHECK_INTERVAL 3600
@@ -115,7 +119,7 @@
static volatile sig_atomic_t term_signal = 0;
-#ifdef HAVE_PAM
+#ifdef WITH_PAM
#include <security/pam_appl.h>
static pam_handle_t *pamh = NULL;
@@ -124,15 +128,7 @@
NULL
};
-#define PAM_FAIL_CHECK if (retcode != PAM_SUCCESS) { \
- fprintf(stderr,"\n%s\n",pam_strerror(pamh, retcode)); \
- syslog(LOG_ERR,"%s",pam_strerror(pamh, retcode)); \
- pam_end(pamh, retcode); exit(1); \
- }
-#define PAM_END { retcode = pam_close_session(pamh,0); \
- pam_end(pamh,retcode); }
-
-#endif /* HAVE_PAM */
+#endif /* WITH_PAM */
/* Signal handlers */
RETSIGTYPE
@@ -293,7 +289,7 @@
char fmt[64];
unsigned long jobno;
int rc;
-#ifdef HAVE_PAM
+#ifdef WITH_PAM
int retcode;
#endif
@@ -450,17 +446,11 @@
fstat(fd_out, &buf);
size = buf.st_size;
-#ifdef HAVE_PAM
- PRIV_START
- retcode = pam_start("atd", pentry->pw_name, &conv, &pamh);
- PAM_FAIL_CHECK;
- retcode = pam_acct_mgmt(pamh, PAM_SILENT);
- PAM_FAIL_CHECK;
- retcode = pam_open_session(pamh, PAM_SILENT);
- PAM_FAIL_CHECK;
- retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED | PAM_SILENT);
- PAM_FAIL_CHECK;
- PRIV_END
+#ifdef WITH_PAM
+ AT_START_PAM;
+ AT_OPEN_PAM_SESSION;
+ closelog();
+ openlog("atd", LOG_PID, LOG_ATD);
#endif
close(STDIN_FILENO);
@@ -475,6 +465,14 @@
char *nul = NULL;
char **nenvp = &nul;
+ char **pam_envp=0L;
+
+ PRIV_START
+#ifdef WITH_PAM
+ pam_envp = pam_getenvlist(pamh);
+ if ( ( pam_envp != 0L ) && (pam_envp[0] != 0L) )
+ nenvp = pam_envp;
+#endif
/* Set up things for the child; we want standard input from the
* input file, and standard output and error sent to our output file.
*/
@@ -493,7 +491,6 @@
close(fd_in);
close(fd_out);
- PRIV_START
nice((tolower((int) queue) - 'a') * 2);
@@ -515,9 +512,9 @@
chdir("/");
- if (execle("/bin/sh", "sh", (char *) NULL, nenvp) != 0)
- perr("Exec failed for /bin/sh");
-
+ execle("/bin/sh", "sh", (char *) NULL, nenvp);
+ perr("Exec failed for /bin/sh");
+ /* perr exits, the PRIV_END is just for nice form */
PRIV_END
}
/* We're the parent. Let's wait.
@@ -530,14 +527,6 @@
*/
waitpid(pid, (int *) NULL, 0);
-#ifdef HAVE_PAM
- PRIV_START
- pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT);
- retcode = pam_close_session(pamh, PAM_SILENT);
- pam_end(pamh, retcode);
- PRIV_END
-#endif
-
/* Send mail. Unlink the output file after opening it, so it
* doesn't hang around after the run.
*/
@@ -568,8 +557,13 @@
unlink(newname);
free(newname);
+#ifdef ATD_MAIL_PROGRAM
if (((send_mail != -1) && (buf.st_size != size)) || (send_mail == 1)) {
+ int mail_pid = -1;
+ mail_pid = fork();
+
+ if ( mail_pid == 0 ) {
PRIV_START
if (initgroups(pentry->pw_name, pentry->pw_gid))
@@ -591,7 +585,20 @@
perr("Exec failed for mail command");
PRIV_END
+ }
+ else if ( mail_pid == -1 ) {
+ syslog(LOG_ERR, "fork of mailer failed: %m");
+ }
+ /* Parent */
+ waitpid(mail_pid, (int *) NULL, 0);
}
+
+#ifdef WITH_PAM
+ AT_CLOSE_PAM;
+ closelog();
+ openlog("atd", LOG_PID, LOG_ATD);
+#endif
+#endif
exit(EXIT_SUCCESS);
}
diff -ur b/config.h.in a/config.h.in
--- b/config.h.in 2022-01-29 17:42:19.000000000 +0100
+++ a/config.h.in 2022-02-23 18:51:31.467570176 +0100
@@ -74,8 +74,8 @@
/* Define to 1 if you have the <nlist.h> header file. */
#undef HAVE_NLIST_H
-/* Define to 1 for PAM support */
-#undef HAVE_PAM
+/* Define if you are building with_pam */
+#undef WITH_PAM
/* Define to 1 if you have the `pstat_getdynamic' function. */
#undef HAVE_PSTAT_GETDYNAMIC
diff -ur b/configure.ac a/configure.ac
--- b/configure.ac 2022-01-29 17:42:19.000000000 +0100
+++ a/configure.ac 2022-02-23 18:53:08.516720324 +0100
@@ -97,7 +97,7 @@
AC_CHECK_FUNCS(getcwd mktime strftime setreuid setresuid sigaction waitpid)
AC_CHECK_HEADERS(security/pam_appl.h, [
PAMLIB="-lpam"
- AC_DEFINE(HAVE_PAM, 1, [Define to 1 for PAM support])
+ AC_DEFINE(WITH_PAM, 1, [Define to 1 for PAM support])
])
dnl Checking for programs
@@ -260,6 +260,13 @@
)
AC_SUBST(DAEMON_USERNAME)
+AC_ARG_WITH(pam,
+[ --with-pam Define to enable pam support ],
+AC_DEFINE(WITH_PAM),
+)
+AC_CHECK_LIB(pam, pam_start, PAMLIB='-lpam -lpam_misc')
+AC_SUBST(PAMLIB)
+
AC_ARG_WITH(selinux,
[ --with-selinux Define to run with selinux (default=check)],
[],
diff -ur b/Makefile.in a/Makefile.in
--- b/Makefile.in 2022-02-23 18:33:26.999892289 +0100
+++ a/Makefile.in 2022-02-23 18:53:28.600751396 +0100
@@ -76,7 +76,7 @@
all: at atd atd.service atrun
at: $(ATOBJECTS)
- $(CC) $(LDFLAGS) -pie -o at $(ATOBJECTS) $(LIBS) $(LEXLIB)
+ $(CC) $(LDFLAGS) -pie -o at $(ATOBJECTS) $(LIBS) $(LEXLIB) $(PAMLIB)
rm -f $(CLONES)
$(LN_S) -f at atq
$(LN_S) -f at atrm
diff -ur b/perm.c a/perm.c
--- b/perm.c 2022-01-29 17:42:19.000000000 +0100
+++ a/perm.c 2022-02-23 18:56:21.401018761 +0100
@@ -51,6 +51,14 @@
#define PRIV_END while(0)
#endif
+#ifdef WITH_PAM
+#include <security/pam_appl.h>
+static pam_handle_t *pamh = NULL;
+static const struct pam_conv conv = {
+ NULL
+};
+#endif
+
/* Structures and unions */
@@ -108,18 +116,45 @@
int
check_permission()
{
- uid_t uid = geteuid();
+ uid_t euid = geteuid(), uid=getuid(), egid=getegid(), gid=getgid();
struct passwd *pentry;
int allow = 0, deny = 1;
- if (uid == 0)
+ int retcode = 0;
+ if (euid == 0)
return 1;
- if ((pentry = getpwuid(uid)) == NULL) {
+ if ((pentry = getpwuid(euid)) == NULL) {
perror("Cannot access user database");
exit(EXIT_FAILURE);
}
+#ifdef WITH_PAM
+/*
+ * We must check if the atd daemon userid will be allowed to gain the job owner user's
+ * credentials with PAM . If not, the user has been denied at(1) usage, eg. with pam_access.
+ */
+ if (setreuid(daemon_uid, daemon_uid) != 0) {
+ fprintf(stderr, "cannot set egid: %s", strerror(errno));
+ exit(1);
+ }
+ if (setregid(daemon_gid, daemon_gid) != 0) {
+ fprintf(stderr, "cannot set euid: %s", strerror(errno));
+ exit(1);
+ }
+
+ AT_START_PAM;
+ AT_CLOSE_PAM;
+ if (setregid(gid,egid) != 0) {
+ fprintf(stderr, "cannot set egid: %s", strerror(errno));
+ exit(1);
+ }
+ if (setreuid(uid,euid) != 0) {
+ fprintf(stderr, "cannot set euid: %s", strerror(errno));
+ exit(1);
+ }
+#endif
+
allow = user_in_file(ETCDIR "/at.allow", pentry->pw_name);
if (allow==0 || allow==1)
return allow;
diff -ur b/privs.h a/privs.h
--- b/privs.h 2022-01-29 17:42:19.000000000 +0100
+++ a/privs.h 2022-02-23 18:58:20.920203690 +0100
@@ -144,3 +144,62 @@
#error "Cannot implement user ID swapping without setreuid or setresuid"
#endif
#endif
+
+#ifdef WITH_PAM
+/* PAM failed after session was open. */
+#define PAM_SESSION_FAIL if (retcode != PAM_SUCCESS) \
+ pam_close_session(pamh,PAM_SILENT);
+
+/* syslog will be logging error messages */
+#ifdef HAVE_UNISTD_H
+#include <syslog.h>
+#endif
+
+/* PAM fail even before opening the session */
+#define PAM_FAIL_CHECK \
+ do { if (retcode != PAM_SUCCESS) { \
+ fprintf(stderr,"PAM failure: %s\n",pam_strerror(pamh, retcode)); \
+ syslog(LOG_ERR,"%s",pam_strerror(pamh, retcode)); \
+ if (pamh) \
+ pam_end(pamh, retcode); \
+ if (setregid(getgid(),getegid()) != 0) { \
+ fprintf(stderr, "cannot set egid: %s", strerror(errno)); \
+ exit(1); \
+ } \
+ if (setreuid(getuid(),geteuid()) != 0) { \
+ fprintf(stderr, "cannot set euid: %s", strerror(errno)); \
+ exit(1); \
+ } \
+ exit(1); \
+ } \
+ } while (0) \
+
+static int pam_session_opened = 0; //global for open session
+
+#define AT_START_PAM { \
+ retcode = pam_start("atd", pentry->pw_name, &conv, &pamh); \
+ PAM_FAIL_CHECK; \
+ retcode = pam_set_item(pamh, PAM_TTY, "atd"); \
+ PAM_FAIL_CHECK; \
+ retcode = pam_acct_mgmt(pamh, PAM_SILENT); \
+ PAM_FAIL_CHECK; \
+}
+
+#define AT_OPEN_PAM_SESSION { \
+ retcode = pam_open_session(pamh, PAM_SILENT); \
+ PAM_FAIL_CHECK; \
+ retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED | PAM_SILENT); \
+ PAM_FAIL_CHECK; \
+ if (retcode == PAM_SUCCESS) \
+ pam_session_opened = 1; \
+}
+
+#define AT_CLOSE_PAM { \
+ if (pam_session_opened != 0) { \
+ pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT); \
+ pam_close_session(pamh, PAM_SILENT); \
+ } \
+ pam_end(pamh, PAM_SUCCESS); \
+}
+
+#endif