libcgroup: A simple pam module (pam_cgroup.so) for task placement in right cgroup

From: Vivek Goyal <vgoyal@redhat.com>

o A simple pam module pam_cgroup for placement of tasks in right cgroup.
  Details are available in documentation.

o This pam module will be included in libcgroup source and not in
  pam sources.

o Copyright notice looks little odd as I copied the original copyright
  notice of pam_limits.c. Any suggestions for improvement are welcome.


Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>



git-svn-id: https://libcg.svn.sourceforge.net/svnroot/libcg/trunk@162 4f4bb910-9a46-0410-90c8-c897d4f1cd53

3 files changed, 188 insertions, 5 deletions

diff --git a/Makefile.in b/Makefile.in
index a36a5f4..90147dd 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -55,6 +55,10 @@ libcgroup.so: api.c libcgroup.h wrapper.c
 test:
 	$(MAKE) -C tests
 
+pam_cgroup.so: pam_cgroup.c
+	$(CC) $(CFLAGS) -shared -fPIC -Wall -o $@ pam_cgroup.c $(LDFLAGS) \
+	$(LIBS) -lpam
+
 install: libcgroup.so cgexec cgclassify
 	$(INSTALL_DATA) -D libcgroup.h $(DESTDIR)$(includedir)/libcgroup.h
 	$(INSTALL) -D libcgroup.so $(DESTDIR)$(libdir)/libcgroup-$(PACKAGE_VERSION).so
@@ -75,4 +79,5 @@ uninstall: libcgroup.so
 
 clean:
 	\rm -f y.tab.c y.tab.h lex.yy.c y.output libcgroup.so cgclassify\
-	libcgroup.so.$(VERSION) cgconfigparser config.log config.status cgexec
+	libcgroup.so.$(VERSION) cgconfigparser config.log config.status cgexec \
+	pam_cgroup.so
diff --git a/README b/README
index 0835004..34ca090 100644
--- a/README
+++ b/README
@@ -50,7 +50,7 @@ cgroups.
 
 - Use pam_cgroup PAM plugin which will make sure users are placed in right
   cgroup at login time and any tasks launch after login, will continue to run
-  in user's cgroup. (PAM module is still on TODO list)
+  in user's cgroup.
 
 - Use command line tool "cgexec" to launch the task in right cgroup.
 
@@ -113,14 +113,15 @@ Section 3:
 To use a pam plugin which will automatically place the task in right
 cgroup upon login.
 
-- Download pam source tree and apply the patch for pam_cgroup module.
 - Build pam_cgroup.so
-	./configure; make
+	make pam_cgroup.so
 - Copy pam_cgroup.so to /lib/security/
 - Edit /etc/pam.d/su to make use of pam_cgroup.so session module upon
   execution of su.
 
-example:  Add following line to the end.
+example:
+	Add following line at the end of /etc/pam.d/su file
+
 session                optional        pam_cgroup.so
 
 - Now launch a shell for a user "xyz" using su and the resulting shell
@@ -129,6 +130,21 @@ session                optional        pam_cgroup.so
 
   ex. "su test1"
 
+Try similar things with other services like sshd.
+
+Note: pam_cgroup.so moves the service providing process in the right cgroup
+      and not the process which will be launched later. Due to parent child
+      relationship, yet to be forked/execed process will launch in right
+      group.
+
+Ex. Lets say user root does "su test1". In this case process "su" is the
+    one providing service (launching a shell) for user "test1". pam_cgroup.so
+    will move process "su" to the user "test1"'s cgroup (Decided by the uid
+    and gid of "test1"). Now once su forks/execs a shell for user test1,
+    final shell is effectively running in the cgroup it should have been
+    running based on /etc/cgrules.conf for user test1.
+
+
 Section 4:
 ----------
 To use cgrulesengd which will move a task to right cgroup based on
diff --git a/pam_cgroup.c b/pam_cgroup.c
new file mode 100644
index 0000000..c4ce633
--- /dev/null
+++ b/pam_cgroup.c
@@ -0,0 +1,162 @@
+/*
+ * Copyright RedHat Inc. 2008
+ *
+ * Author:      Vivek Goyal <vgoyal@redhat.com>
+ *
+ * Derived from pam_limits.c. Original Copyright notice follows.
+ *
+ * Copyright (c) Cristian Gafton, 1996-1997, <gafton@redhat.com>
+ *                                              All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU Public License, in which case the provisions of the GPL are
+ * required INSTEAD OF the above restrictions.  (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * End of original copyright notice.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <ctype.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <syslog.h>
+#include <libcgroup.h>
+#include <pwd.h>
+
+/*
+ * Module defines
+ */
+
+#define PAM_SM_SESSION
+
+#include <security/pam_modules.h>
+#include <security/_pam_macros.h>
+#include <security/pam_modutil.h>
+#include <security/pam_ext.h>
+
+/* argument parsing */
+
+#define PAM_DEBUG_ARG       0x0001
+
+static int _pam_parse(const pam_handle_t *pamh, int argc, const char **argv)
+{
+    int ctrl = 0;
+
+    /* step through arguments */
+    for (ctrl = 0; argc-- > 0; ++argv) {
+	if (!strcmp(*argv, "debug"))
+		ctrl |= PAM_DEBUG_ARG;
+	else
+		pam_syslog(pamh, LOG_ERR, "unknown option: %s", *argv);
+    }
+
+    return ctrl;
+}
+
+/* now the session stuff */
+PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags,
+					int argc, const char **argv)
+{
+	pid_t pid;
+	int ctrl, ret;
+	char *user_name;
+	struct passwd *pwd;
+
+	D(("called."));
+
+	ctrl = _pam_parse(pamh, argc, argv);
+
+	ret = pam_get_item(pamh, PAM_USER, (void *) &user_name);
+	if (user_name == NULL || ret != PAM_SUCCESS)  {
+		pam_syslog(pamh, LOG_ERR, "open_session - error recovering"
+				"username");
+		return PAM_SESSION_ERR;
+	}
+
+	pwd = pam_modutil_getpwnam(pamh, user_name);
+	if (!pwd) {
+		if (ctrl & PAM_DEBUG_ARG)
+			pam_syslog(pamh, LOG_ERR, "open_session username"
+					" '%s' does not exist", user_name);
+		return PAM_SESSION_ERR;
+	}
+
+	D(("user name is %s", user_name));
+
+	/* Initialize libcg */
+	ret = cgroup_init();
+	if (ret) {
+		if (ctrl & PAM_DEBUG_ARG)
+			pam_syslog(pamh, LOG_ERR, "libcgroup initialization"
+							" failed");
+		return PAM_SESSION_ERR;
+	}
+
+	D(("Initialized libcgroup successfuly."));
+
+	/* Determine the pid of the task */
+	pid = getpid();
+
+	/* Note: We are using default gid here. Is there a way to determine
+	 * under what egid service will be provided?
+	 */
+	ret = cgroup_change_cgroup_uid_gid(pwd->pw_uid, pwd->pw_gid, pid);
+	if (ret) {
+		if (ctrl & PAM_DEBUG_ARG)
+			pam_syslog(pamh, LOG_ERR, "Change of cgroup for process"
+				" with username %s failed.\n", user_name);
+		return PAM_SESSION_ERR;
+	}
+
+	if (ctrl & PAM_DEBUG_ARG)
+		pam_syslog(pamh, LOG_DEBUG, "Changed cgroup for process %d"
+				"  with username %s.\n", pid, user_name);
+
+	return PAM_SUCCESS;
+}
+
+PAM_EXTERN int pam_sm_close_session(pam_handle_t *pamh, int flags, int argc,
+					const char **argv)
+{
+	D(("called pam_cgroup close session"));
+
+	/* nothing to do yet */
+	return PAM_SUCCESS;
+}