0.77: please submit patches for this section with actual code/doc
patches!
+* pam_unix and pam_pwdb: by default turn off the SIGCHLD handler while
+ running the helper binary (patch from Nalin) added the "noreap"
+ module argument to both of these modules to turn off this new
+ default. (Bug 476963 - agmorgan).
* updated CHANGELOG and configure.in for 0.77 work.
0.76: Mon Jul 8 21:44:59 PDT 2002
<tt/try_first_pass/;
<tt/nullok/;
<tt/nodelay/;
-<tt/likeauth/
+<tt/likeauth/;
+<tt/noreap/
<tag><bf>Description:</bf></tag>
is very simple and will only check the password of the user invoking
it. It is called transparently on behalf of the user by the
authenticating component of this module. In this way it is possible
-for applications like <em>xlock</em> to work without being setuid-root.
+for applications like <em>xlock</em> to work without being
+setuid-root. The module, by default, will temporarily turn off
+<tt/SIGCHLD/ handling for the duration of execution of the helper
+binary. This is generally the right thing to do, as many applications
+are not prepared to handle this signal from a child they didn't know
+was <tt/fork()/d. The <tt/noreap/ module argument can be used to
+suppress this temporary shielding and may be needed for use with
+certain applications.
<p>
The <tt>likeauth</tt> argument makes the module return the same value
<tt/use_first_pass/;
<tt/try_first_pass/;
<tt/nullok/;
-<tt/nodelay/
+<tt/nodelay/;
+<tt/noreap/
<tag><bf>Description:</bf></tag>
authentication as a whole fail. The default action is for the module
to request a delay-on-failure of the order of one second.
-<p>
-Remaining arguments, supported by the other functions of this module,
-are silently ignored. Other arguments are logged as errors through
-<tt/syslog(3)/.
-
<p>
A helper binary, <tt>unix_chkpwd</tt>, is provided to check the user's
password when it is stored in a read protected database. This binary
is very simple and will only check the password of the user invoking
it. It is called transparently on behalf of the user by the
authenticating component of this module. In this way it is possible
-for applications like <em>xlock</em> to work without being setuid-root.
+for applications like <em>xlock</em> to work without being
+setuid-root. The module, by default, will temporarily turn off
+<tt/SIGCHLD/ handling for the duration of execution of the helper
+binary. This is generally the right thing to do, as many applications
+are not prepared to handle this signal from a child they didn't know
+was <tt/fork()/d. The <tt/noreap/ module argument can be used to
+suppress this temporary shielding and may be needed for use with
+certain applications.
+
+<p>
+Remaining arguments, supported by the other functions of this module,
+are silently ignored. Other arguments are logged as errors through
+<tt/syslog(3)/.
<tag><bf>Examples/suggested usage:</bf></tag>
<title>The Linux-PAM System Administrators' Guide
<author>Andrew G. Morgan, <tt>morgan@kernel.org</tt>
-<date>DRAFT v0.76 2002/06/26
+<date>DRAFT v0.77 2002/07/10
<abstract>
This manual documents what a system-administrator needs to know about
the <bf>Linux-PAM</bf> library. It covers the correct syntax of the
#define UNIX_UNIX 19 /* wish to use /etc/passwd for pwd */
#define UNIX_BIGCRYPT 20 /* use DEC-C2 crypt()^x function */
#define UNIX_LIKE_AUTH 21 /* need to auth for setcred to work */
+#define UNIX_NOREAP 22 /* don't reap child process */
/* -------------- */
-#define UNIX_CTRLS_ 22 /* number of ctrl arguments defined */
+#define UNIX_CTRLS_ 23 /* number of ctrl arguments defined */
static const UNIX_Ctrls unix_args[UNIX_CTRLS_] = {
/* UNIX_UNIX */ { "unix", _ALL_ON_^(050000), 01000000 },
/* UNIX_BIGCRYPT */ { "bigcrypt", _ALL_ON_^(020000), 02000000 },
/* UNIX_LIKE_AUTH */ { "likeauth", _ALL_ON_, 04000000 },
+/* UNIX_NOREAP */ {"noreap", _ALL_ON_, 010000000 },
};
#define UNIX_DEFAULTS (unix_args[UNIX__NONULL].flag)
* verify the password of a user
*/
+#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
static int pwdb_run_helper_binary(pam_handle_t *pamh, const char *passwd,
- const char *user)
+ unsigned int ctrl, const char *user)
{
int retval, child, fds[2];
+ void (*sighandler)(int) = NULL;
D(("called."));
/* create a pipe for the password */
return PAM_AUTH_ERR;
}
+ if (off(UNIX_NOREAP, ctrl)) {
+ /*
+ * This code arranges that the demise of the child does not cause
+ * the application to receive a signal it is not expecting - which
+ * may kill the application or worse.
+ *
+ * The "noreap" module argument is provided so that the admin can
+ * override this behavior.
+ */
+ sighandler = signal(SIGCHLD, SIG_IGN);
+ }
+
/* fork */
child = fork();
if (child == 0) {
retval = PAM_AUTH_ERR;
}
+ if (sighandler != NULL) {
+ (void) signal(SIGCHLD, sighandler); /* restore old signal handler */
+ }
+
D(("returning %d", retval));
return retval;
}
if (geteuid()) {
/* we are not root perhaps this is the reason? Run helper */
D(("running helper binary"));
- retval = pwdb_run_helper_binary(pamh, p, name);
+ retval = pwdb_run_helper_binary(pamh, p, ctrl, name);
} else {
retval = PAM_AUTHINFO_UNAVAIL;
_log_err(LOG_ALERT, "get passwd; %s", pwdb_strerror(retval));
#include <limits.h>
#include <utmp.h>
#include <errno.h>
+#include <signal.h>
#include <security/_pam_macros.h>
#include <security/pam_modules.h>
unsigned int ctrl, const char *user)
{
int retval, child, fds[2];
+ void (*sighandler)(int) = NULL;
D(("called."));
/* create a pipe for the password */
return PAM_AUTH_ERR;
}
+ if (off(UNIX_NOREAP, ctrl)) {
+ /*
+ * This code arranges that the demise of the child does not cause
+ * the application to receive a signal it is not expecting - which
+ * may kill the application or worse.
+ *
+ * The "noreap" module argument is provided so that the admin can
+ * override this behavior.
+ */
+ sighandler = signal(SIGCHLD, SIG_IGN);
+ }
+
/* fork */
child = fork();
if (child == 0) {
retval = PAM_AUTH_ERR;
}
+ if (sighandler != NULL) {
+ (void) signal(SIGCHLD, sighandler); /* restore old signal handler */
+ }
+
D(("returning %d", retval));
return retval;
}
#define UNIX_BIGCRYPT 18 /* use DEC-C2 crypt()^x function */
#define UNIX_LIKE_AUTH 19 /* need to auth for setcred to work */
#define UNIX_REMEMBER_PASSWD 20 /* Remember N previous passwords */
+#define UNIX_NOREAP 21 /* don't reap child process */
/* -------------- */
-#define UNIX_CTRLS_ 21 /* number of ctrl arguments defined */
+#define UNIX_CTRLS_ 22 /* number of ctrl arguments defined */
static const UNIX_Ctrls unix_args[UNIX_CTRLS_] =
/* UNIX_BIGCRYPT */ {"bigcrypt", _ALL_ON_^(020000), 0400000},
/* UNIX_LIKE_AUTH */ {"likeauth", _ALL_ON_, 01000000},
/* UNIX_REMEMBER_PASSWD */ {"remember=", _ALL_ON_, 02000000},
+/* UNIX_NOREAP */ {"noreap", _ALL_ON_, 04000000},
};
#define UNIX_DEFAULTS (unix_args[UNIX__NONULL].flag)
projects / linux-pam / commitdiff