[PATCH v2 3/4] chsh: Add libuser support

Cody Maloney
2013-01-13T09:12:59Z

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This is based directly on lchsh which is a part of libuser. libuser.{c,h}
exist because exactly the same code is needed for both chsh and chfn.

Signed-off-by: Cody Maloney <cmaloney@theoreticalchaos.com>
---
login-utils/Makemodule.am | 3 ++
login-utils/chsh.c | 24 ++++++++++++--
login-utils/libuser.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++
login-utils/libuser.h | 14 ++++++++
4 files changed, 123 insertions(+), 2 deletions(-)
create mode 100644 login-utils/libuser.c
create mode 100644 login-utils/libuser.h

diff --git a/login-utils/Makemodule.am b/login-utils/Makemodule.am
index ee85329..0c57118 100644
--- a/login-utils/Makemodule.am
+++ b/login-utils/Makemodule.am
@@ -73,6 +73,9 @@ chfn_chsh_ldadd = libcommon.la -lpam -lpam_misc
if HAVE_USER
chfn_chsh_ldflags += $(LIBUSER_LIBS)
chfn_chsh_cflags += $(LIBUSER_CFLAGS)
+chfn_chsh_sources+= \
+ login-utils/libuser.c \
+ login-utils/libuser.h
endif

if HAVE_SELINUX
diff --git a/login-utils/chsh.c b/login-utils/chsh.c
index 4113df5..fa2fa84 100644
--- a/login-utils/chsh.c
+++ b/login-utils/chsh.c
@@ -1,6 +1,7 @@
/*
* chsh.c -- change your login shell
* (c) 1994 by salvatore valente <svalente@athena.mit.edu>
+ * (c) 2012 by Cody Maloney <cmaloney@theoreticalchaos.com>
*
* this program is free software. you can redistribute it and
* modify it under the terms of the gnu general public license.
@@ -17,7 +18,7 @@
* suggestion from Zefram. Disallowing users with shells not in /etc/shells
* from changing their shell.
*
- * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@pld.ORG.PL>
+ * 1999-02-22 Arkadiusz MiÂ¶kiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*/

@@ -32,7 +33,6 @@
#include <sys/types.h>
#include <unistd.h>

-#include "auth.h"
#include "c.h"
#include "env.h"
#include "closestream.h"
@@ -48,6 +48,14 @@
# include "selinux_utils.h"
#endif

+
+#ifdef HAVE_LIBUSER
+# include <libuser/user.h>
+# include "libuser.h"
+#else
+# include "auth.h"
+#endif
+
struct sinfo {
char *username;
char *shell;
@@ -131,7 +139,12 @@ int main(int argc, char **argv)
oldshell = _PATH_BSHELL; /* default */

/* reality check */
+#ifdef HAVE_LIBUSER
+ /* If we're setuid and not really root, disallow the password change. */
+ if (geteuid() != getuid() && uid != pw->pw_uid) {
+#else
if (uid != 0 && uid != pw->pw_uid) {
+#endif
errno = EACCES;
err(EXIT_FAILURE,
_("running UID doesn't match UID of user we're "
@@ -147,9 +160,11 @@ int main(int argc, char **argv)

printf(_("Changing shell for %s.\n"), pw->pw_name);

+#ifndef HAVE_LIBUSER
if(!auth_pam("chsh", uid, pw->pw_name)) {
return EXIT_FAILURE;
}
+#endif

if (!shell) {
shell = prompt(_("New shell"), oldshell);
@@ -162,10 +177,15 @@ int main(int argc, char **argv)

if (strcmp(oldshell, shell) == 0)
errx(EXIT_SUCCESS, _("Shell not changed."));
+
+#ifdef HAVE_LIBUSER
+ set_value_libuser("chsh", pw->pw_name, uid, LU_LOGINSHELL, shell);
+#else
pw->pw_shell = shell;
if (setpwnam(pw) < 0)
err(EXIT_FAILURE, _("setpwnam failed\n"
"Shell *NOT* changed. Try again later."));
+#endif

printf(_("Shell changed.\n"));
return EXIT_SUCCESS;
diff --git a/login-utils/libuser.c b/login-utils/libuser.c
new file mode 100644
index 0000000..9a3e3b1
--- /dev/null
+++ b/login-utils/libuser.c
@@ -0,0 +1,84 @@
+/*
+ * libuser.c -- Utilize libuser to set a user attribute
+ * (c) 2012 by Cody Maloney <cmaloney@theoreticalchaos.com>
+ *
+ * this program is free software. you can redistribute it and
+ * modify it under the terms of the gnu general public license.
+ * there is no warranty.
+ *
+ */
+
+#include "libuser.h"
+
+#include <grp.h>
+#include <libuser/user.h>
+#include <unistd.h>
+
+#include "auth.h"
+#include "c.h"
+#include "nls.h"
+
+static int auth_lu(const char *service_name, struct lu_context *ctx, uid_t uid,
+ const char *username);
+
+static int auth_lu(const char *service_name, struct lu_context *ctx, uid_t uid,
+ const char *username) {
+ if(!lu_uses_elevated_privileges(ctx)) {
+ /* Drop privileges */
+ if (setegid(getgid()) == -1) {
+ errx(EXIT_FAILURE, _("Couldn't drop group privileges"));
+ return FALSE;
+ }
+ if (seteuid(getuid()) == -1) {
+ errx(EXIT_FAILURE, _("Couldn't drop group privileges"));
+ return FALSE;
+ }
+ if (initgroups(username, 0)) {
+ errx(EXIT_FAILURE, _("Couldn't drop group privileges"));
+ return FALSE;
+ }
+ return TRUE;
+ }
+
+ return auth_pam(service_name, uid, username);
+}
+
+int set_value_libuser(const char *service_name, const char *username, uid_t uid,
+ const char *attr, const char *val) {
+ struct lu_context *ctx;
+ struct lu_error *error = NULL;
+ struct lu_ent *ent;
+
+ ctx = lu_start(username, lu_user, NULL, NULL, lu_prompt_console_quiet,
+ NULL, &error);
+ if (ctx == NULL) {
+ err(EXIT_FAILURE, _("Error initializing %s: %s.\n"), PACKAGE,
+ lu_strerror(error));
+ return FALSE;
+ }
+
+ if(!auth_lu(service_name, ctx, uid, username)) {
+ errno = EACCES;
+ err(EXIT_FAILURE, _("Permisison denied for changing user attribute"));
+ return FALSE;
+ }
+
+ /* Look up the user's record. */
+ ent = lu_ent_new();
+ if (lu_user_lookup_name(ctx, username, ent, &error) == FALSE) {
+ lu_end(ctx);
+ err(EXIT_FAILURE, _("user \"%s\" does not exist."), username);
+ return FALSE;
+ }
+
+ lu_ent_set_string(ent, attr, val);
+ if (!lu_user_modify(ctx, ent, &error)) {
+ lu_ent_free(ent);
+ lu_end(ctx);
+ err(EXIT_FAILURE, _("Shell not changed: %s\n"), lu_strerror(error));
+ return FALSE;
+ }
+ lu_ent_free(ent);
+ lu_end(ctx);
+ return TRUE;
+}
diff --git a/login-utils/libuser.h b/login-utils/libuser.h
new file mode 100644
index 0000000..7454b99
--- /dev/null
+++ b/login-utils/libuser.h
@@ -0,0 +1,14 @@
+/*
+ * libuser.h -- Utilize libuser to set a user attribute
+ * (c) 2012 by Cody Maloney <cmaloney@theoreticalchaos.com>
+ *
+ * this program is free software. you can redistribute it and
+ * modify it under the terms of the gnu general public license.
+ * there is no warranty.
+ *
+ */
+
+#include <sys/types.h>
+
+extern int set_value_libuser(const char *service_name, const char *username,
+ uid_t uid, const char *attr, const char *val);
--
1.8.1