[PATCH] Keys: Make request-key create an authorisation key

The attached patch makes the following changes:

 (1) There's a new special key type called ".request_key_auth".

     This is an authorisation key for when one process requests a key and
     another process is started to construct it. This type of key cannot be
     created by the user; nor can it be requested by kernel services.

     Authorisation keys hold two references:

     (a) Each refers to a key being constructed. When the key being
     	 constructed is instantiated the authorisation key is revoked,
     	 rendering it of no further use.

     (b) The "authorising process". This is either:

     	 (i) the process that called request_key(), or:

     	 (ii) if the process that called request_key() itself had an
     	      authorisation key in its session keyring, then the authorising
     	      process referred to by that authorisation key will also be
     	      referred to by the new authorisation key.

	 This means that the process that initiated a chain of key requests
	 will authorise the lot of them, and will, by default, wind up with
	 the keys obtained from them in its keyrings.

 (2) request_key() creates an authorisation key which is then passed to
     /sbin/request-key in as part of a new session keyring.

 (3) When request_key() is searching for a key to hand back to the caller, if
     it comes across an authorisation key in the session keyring of the
     calling process, it will also search the keyrings of the process
     specified therein and it will use the specified process's credentials
     (fsuid, fsgid, groups) to do that rather than the calling process's
     credentials.

     This allows a process started by /sbin/request-key to find keys belonging
     to the authorising process.

 (4) A key can be read, even if the process executing KEYCTL_READ doesn't have
     direct read or search permission if that key is contained within the
     keyrings of a process specified by an authorisation key found within the
     calling process's session keyring, and is searchable using the
     credentials of the authorising process.

     This allows a process started by /sbin/request-key to read keys belonging
     to the authorising process.

 (5) The magic KEY_SPEC_*_KEYRING key IDs when passed to KEYCTL_INSTANTIATE or
     KEYCTL_NEGATE will specify a keyring of the authorising process, rather
     than the process doing the instantiation.

 (6) One of the process keyrings can be nominated as the default to which
     request_key() should attach new keys if not otherwise specified. This is
     done with KEYCTL_SET_REQKEY_KEYRING and one of the KEY_REQKEY_DEFL_*
     constants. The current setting can also be read using this call.

 (7) request_key() is partially interruptible. If it is waiting for another
     process to finish constructing a key, it can be interrupted. This permits
     a request-key cycle to be broken without recourse to rebooting.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-Off-By: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 59 insertions, 10 deletions

diff --git a/include/linux/key-ui.h b/include/linux/key-ui.h
index 159ca8d54e9a..cc326174a808 100644
--- a/include/linux/key-ui.h
+++ b/include/linux/key-ui.h
@@ -1,4 +1,4 @@
-/* key-ui.h: key userspace interface stuff for use by keyfs
+/* key-ui.h: key userspace interface stuff
  *
  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
@@ -84,8 +84,45 @@ static inline int key_any_permission(const struct key *key, key_perm_t perm)
         return kperm != 0;
 }
 
+static inline int key_task_groups_search(struct task_struct *tsk, gid_t gid)
+{
+        int ret;
+
+        task_lock(tsk);
+        ret = groups_search(tsk->group_info, gid);
+        task_unlock(tsk);
+        return ret;
+}
+
+static inline int key_task_permission(const struct key *key,
+                                      struct task_struct *context,
+                                      key_perm_t perm)
+{
+        key_perm_t kperm;
+
+        if (key->uid == context->fsuid) {
+                kperm = key->perm >> 16;
+        }
+        else if (key->gid != -1 &&
+                 key->perm & KEY_GRP_ALL && (
+                         key->gid == context->fsgid ||
+                         key_task_groups_search(context, key->gid)
+                         )
+                 ) {
+                kperm = key->perm >> 8;
+        }
+        else {
+                kperm = key->perm;
+        }
+
+        kperm = kperm & perm & KEY_ALL;
+
+        return kperm == perm;
+
+}
 
-extern struct key *lookup_user_key(key_serial_t id, int create, int part,
+extern struct key *lookup_user_key(struct task_struct *context,
+                                   key_serial_t id, int create, int partial,
                                    key_perm_t perm);
 
 extern long join_session_keyring(const char *name);
diff --git a/include/linux/key.h b/include/linux/key.h
index 2bfbf88d2740..970bbd916cf4 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -199,10 +199,12 @@ extern int key_payload_reserve(struct key *key, size_t datalen);
 extern int key_instantiate_and_link(struct key *key,
                                     const void *data,
                                     size_t datalen,
-                                    struct key *keyring);
+                                    struct key *keyring,
+                                    struct key *instkey);
 extern int key_negate_and_link(struct key *key,
                                unsigned timeout,
-                               struct key *keyring);
+                               struct key *keyring,
+                               struct key *instkey);
 extern void key_revoke(struct key *key);
 extern void key_put(struct key *key);
 
@@ -245,9 +247,6 @@ extern struct key *keyring_search(struct key *keyring,
                                   struct key_type *type,
                                   const char *description);
 
-extern struct key *search_process_keyrings(struct key_type *type,
-                                           const char *description);
-
 extern int keyring_add_key(struct key *keyring,
                            struct key *key);
 
diff --git a/include/linux/keyctl.h b/include/linux/keyctl.h
index 381dedc370a3..8d7c59a29e09 100644
--- a/include/linux/keyctl.h
+++ b/include/linux/keyctl.h
@@ -20,6 +20,16 @@
 #define KEY_SPEC_USER_SESSION_KEYRING   -5      /* - key ID for UID-session keyring */
 #define KEY_SPEC_GROUP_KEYRING          -6      /* - key ID for GID-specific keyring */
 
+/* request-key default keyrings */
+#define KEY_REQKEY_DEFL_NO_CHANGE               -1
+#define KEY_REQKEY_DEFL_DEFAULT                 0
+#define KEY_REQKEY_DEFL_THREAD_KEYRING          1
+#define KEY_REQKEY_DEFL_PROCESS_KEYRING         2
+#define KEY_REQKEY_DEFL_SESSION_KEYRING         3
+#define KEY_REQKEY_DEFL_USER_KEYRING            4
+#define KEY_REQKEY_DEFL_USER_SESSION_KEYRING    5
+#define KEY_REQKEY_DEFL_GROUP_KEYRING           6
+
 /* keyctl commands */
 #define KEYCTL_GET_KEYRING_ID           0       /* ask for a keyring's ID */
 #define KEYCTL_JOIN_SESSION_KEYRING     1       /* join or start named session keyring */
@@ -35,5 +45,6 @@
 #define KEYCTL_READ                     11      /* read a key or keyring's contents */
 #define KEYCTL_INSTANTIATE              12      /* instantiate a partially constructed key */
 #define KEYCTL_NEGATE                   13      /* negate a partially constructed key */
+#define KEYCTL_SET_REQKEY_KEYRING       14      /* set default request-key keyring */
 
 #endif /*  _LINUX_KEYCTL_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 901742f92389..2c69682b0444 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -561,9 +561,10 @@ struct group_info {
                 groups_free(group_info); \
 } while (0)
 
-struct group_info *groups_alloc(int gidsetsize);
-void groups_free(struct group_info *group_info);
-int set_current_groups(struct group_info *group_info);
+extern struct group_info *groups_alloc(int gidsetsize);
+extern void groups_free(struct group_info *group_info);
+extern int set_current_groups(struct group_info *group_info);
+extern int groups_search(struct group_info *group_info, gid_t grp);
 /* access the groups "array" with this macro */
 #define GROUP_AT(gi, i) \
     ((gi)->blocks[(i)/NGROUPS_PER_BLOCK][(i)%NGROUPS_PER_BLOCK])
@@ -660,6 +661,7 @@ struct task_struct {
         struct user_struct *user;
 #ifdef CONFIG_KEYS
         struct key *thread_keyring;     /* keyring private to this thread */
+        unsigned char jit_keyring;      /* default keyring to attach requested keys to */
 #endif
         int oomkilladj; /* OOM kill score adjustment (bit shift). */
         char comm[TASK_COMM_LEN]; /* executable name excluding path