[PATCH 1/3] Keys: Pass session keyring to call_usermodehelper() [try #2]

David Howells
2005-03-24T11:39:56Z

The attached patch makes it possible to pass a session keyring through to the
process spawned by call_usermodehelper(). This allows patch 3/3 to pass an
authorisation key through to /sbin/request-key, thus permitting better access
controls when doing just-in-time key creation.

Signed-Off-By: David Howells <dhowells@redhat.com>
---
warthog>diffstat -p1 keys-umhelper-2612rc1mm1-2.diff
include/linux/key.h | 10 +++++++++-
include/linux/kmod.h | 12 +++++++++++-
kernel/kmod.c | 15 ++++++++++++---
security/keys/request_key.c | 2 +-
4 files changed, 33 insertions(+), 6 deletions(-)

diff -uNrp linux-2.6.12-rc1-mm1/include/linux/key.h linux-2.6.12-rc1-mm1-keys-umhelper/include/linux/key.h
--- linux-2.6.12-rc1-mm1/include/linux/key.h 2005-03-23 17:22:44.000000000 +0000
+++ linux-2.6.12-rc1-mm1-keys-umhelper/include/linux/key.h 2005-03-24 11:26:24.684060442 +0000
@@ -273,14 +273,22 @@ extern void key_fsuid_changed(struct tas
extern void key_fsgid_changed(struct task_struct *tsk);
extern void key_init(void);

+#define __install_session_keyring(tsk, keyring) \
+({ \
+ struct key *old_session = tsk->signal->session_keyring; \
+ tsk->signal->session_keyring = keyring; \
+ old_session; \
+})
+
#else /* CONFIG_KEYS */

#define key_validate(k) 0
#define key_serial(k) 0
-#define key_get(k) NULL
+#define key_get(k) ({ NULL; })
#define key_put(k) do { } while(0)
#define alloc_uid_keyring(u) 0
#define switch_uid_keyring(u) do { } while(0)
+#define __install_session_keyring(t, k) ({ NULL; })
#define copy_keys(f,t) 0
#define copy_thread_group_keys(t) 0
#define exit_keys(t) do { } while(0)
diff -uNrp linux-2.6.12-rc1-mm1/include/linux/kmod.h linux-2.6.12-rc1-mm1-keys-umhelper/include/linux/kmod.h
--- linux-2.6.12-rc1-mm1/include/linux/kmod.h 2005-01-04 11:13:54.000000000 +0000
+++ linux-2.6.12-rc1-mm1-keys-umhelper/include/linux/kmod.h 2005-03-24 11:12:14.903253166 +0000
@@ -34,7 +34,17 @@ static inline int request_module(const c
#endif

#define try_then_request_module(x, mod...) ((x) ?: (request_module(mod), (x)))
-extern int call_usermodehelper(char *path, char *argv[], char *envp[], int wait);
+
+struct key;
+extern int call_usermodehelper_keys(char *path, char *argv[], char *envp[],
+ struct key *session_keyring, int wait);
+
+static inline int
+call_usermodehelper(char *path, char **argv, char **envp, int wait)
+{
+ return call_usermodehelper_keys(path, argv, envp, NULL, wait);
+}
+
extern void usermodehelper_init(void);

#endif /* __LINUX_KMOD_H__ */
diff -uNrp linux-2.6.12-rc1-mm1/kernel/kmod.c linux-2.6.12-rc1-mm1-keys-umhelper/kernel/kmod.c
--- linux-2.6.12-rc1-mm1/kernel/kmod.c 2005-01-04 11:13:56.000000000 +0000
+++ linux-2.6.12-rc1-mm1-keys-umhelper/kernel/kmod.c 2005-03-24 11:15:25.610527168 +0000
@@ -120,6 +120,7 @@ struct subprocess_info {
char *path;
char **argv;
char **envp;
+ struct key *ring;
int wait;
int retval;
};
@@ -130,16 +131,21 @@ struct subprocess_info {
static int ____call_usermodehelper(void *data)
{
struct subprocess_info *sub_info = data;
+ struct key *old_session;
int retval;

- /* Unblock all signals. */
+ /* Unblock all signals and set the session keyring. */
+ key_get(sub_info->ring);
flush_signals(current);
spin_lock_irq(&current->sighand->siglock);
+ old_session = __install_session_keyring(current, sub_info->ring);
flush_signal_handlers(current, 1);
sigemptyset(&current->blocked);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);

+ key_put(old_session);
+
/* We can run anywhere, unlike our parent keventd(). */
set_cpus_allowed(current, CPU_MASK_ALL);

@@ -211,10 +217,11 @@ static void __call_usermodehelper(void *
}

/**
- * call_usermodehelper - start a usermode application
+ * call_usermodehelper_keys - start a usermode application
* @path: pathname for the application
* @argv: null-terminated argument list
* @envp: null-terminated environment list
+ * @session_keyring: session keyring for process (NULL for an empty keyring)
* @wait: wait for the application to finish and return status.
*
* Runs a user-space application. The application is started
@@ -224,7 +231,8 @@ static void __call_usermodehelper(void *
* Must be called from process context. Returns a negative error code
* if program was not execed successfully, or 0.
*/
-int call_usermodehelper(char *path, char **argv, char **envp, int wait)
+int call_usermodehelper_keys(char *path, char **argv, char **envp,
+ struct key *session_keyring, int wait)
{
DECLARE_COMPLETION(done);
struct subprocess_info sub_info = {
@@ -232,6 +240,7 @@ int call_usermodehelper(char *path, char
.path = path,
.argv = argv,
.envp = envp,
+ .ring = session_keyring,
.wait = wait,
.retval = 0,
};
diff -uNrp linux-2.6.12-rc1-mm1/security/keys/request_key.c linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/request_key.c
--- linux-2.6.12-rc1-mm1/security/keys/request_key.c 2005-03-23 17:22:46.000000000 +0000
+++ linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/request_key.c 2005-03-24 11:12:46.125678832 +0000
@@ -88,7 +88,7 @@ static int call_request_key(struct key *
argv[i] = NULL;

/* do it */
- return call_usermodehelper(argv[0], argv, envp, 1);
+ return call_usermodehelper_keys(argv[0], argv, envp, NULL, 1);

} /* end call_request_key() */