[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>

1 files changed, 118 insertions, 58 deletions

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index cedb7326de29..fea262860ea0 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1,6 +1,6 @@
 /* keyctl.c: userspace keyctl operations
  *
- * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
@@ -49,6 +49,13 @@ asmlinkage long sys_add_key(const char __user *_type,
                 goto error;
         type[31] = '\0';
 
+        if (!type[0])
+                goto error;
+
+        ret = -EPERM;
+        if (type[0] == '.')
+                goto error;
+
         ret = -EFAULT;
         dlen = strnlen_user(_description, PAGE_SIZE - 1);
         if (dlen <= 0)
@@ -82,7 +89,7 @@ asmlinkage long sys_add_key(const char __user *_type,
         }
 
         /* find the target keyring (which must be writable) */
-        keyring = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
         if (IS_ERR(keyring)) {
                 ret = PTR_ERR(keyring);
                 goto error3;
@@ -181,7 +188,7 @@ asmlinkage long sys_request_key(const char __user *_type,
         /* get the destination keyring if specified */
         dest = NULL;
         if (destringid) {
-                dest = lookup_user_key(destringid, 1, 0, KEY_WRITE);
+                dest = lookup_user_key(NULL, destringid, 1, 0, KEY_WRITE);
                 if (IS_ERR(dest)) {
                         ret = PTR_ERR(dest);
                         goto error3;
@@ -196,23 +203,15 @@ asmlinkage long sys_request_key(const char __user *_type,
         }
 
         /* do the search */
-        key = request_key(ktype, description, callout_info);
+        key = request_key_and_link(ktype, description, callout_info, dest);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error5;
         }
 
-        /* link the resulting key to the destination keyring */
-        if (dest) {
-                ret = key_link(dest, key);
-                if (ret < 0)
-                        goto error6;
-        }
-
         ret = key->serial;
 
- error6:
-        key_put(key);
+        key_put(key);
  error5:
         key_type_put(ktype);
  error4:
@@ -237,7 +236,7 @@ long keyctl_get_keyring_ID(key_serial_t id, int create)
         struct key *key;
         long ret;
 
-        key = lookup_user_key(id, create, 0, KEY_SEARCH);
+        key = lookup_user_key(NULL, id, create, 0, KEY_SEARCH);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error;
@@ -324,7 +323,7 @@ long keyctl_update_key(key_serial_t id,
         }
 
         /* find the target key (which must be writable) */
-        key = lookup_user_key(id, 0, 0, KEY_WRITE);
+        key = lookup_user_key(NULL, id, 0, 0, KEY_WRITE);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error2;
@@ -352,7 +351,7 @@ long keyctl_revoke_key(key_serial_t id)
         struct key *key;
         long ret;
 
-        key = lookup_user_key(id, 0, 0, KEY_WRITE);
+        key = lookup_user_key(NULL, id, 0, 0, KEY_WRITE);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error;
@@ -378,7 +377,7 @@ long keyctl_keyring_clear(key_serial_t ringid)
         struct key *keyring;
         long ret;
 
-        keyring = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
         if (IS_ERR(keyring)) {
                 ret = PTR_ERR(keyring);
                 goto error;
@@ -404,13 +403,13 @@ long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
         struct key *keyring, *key;
         long ret;
 
-        keyring = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
         if (IS_ERR(keyring)) {
                 ret = PTR_ERR(keyring);
                 goto error;
         }
 
-        key = lookup_user_key(id, 1, 0, KEY_LINK);
+        key = lookup_user_key(NULL, id, 1, 0, KEY_LINK);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error2;
@@ -438,13 +437,13 @@ long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
         struct key *keyring, *key;
         long ret;
 
-        keyring = lookup_user_key(ringid, 0, 0, KEY_WRITE);
+        keyring = lookup_user_key(NULL, ringid, 0, 0, KEY_WRITE);
         if (IS_ERR(keyring)) {
                 ret = PTR_ERR(keyring);
                 goto error;
         }
 
-        key = lookup_user_key(id, 0, 0, 0);
+        key = lookup_user_key(NULL, id, 0, 0, 0);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error2;
@@ -475,16 +474,29 @@ long keyctl_describe_key(key_serial_t keyid,
                          char __user *buffer,
                          size_t buflen)
 {
-        struct key *key;
+        struct key *key, *instkey;
         char *tmpbuf;
         long ret;
 
-        key = lookup_user_key(keyid, 0, 1, KEY_VIEW);
+        key = lookup_user_key(NULL, keyid, 0, 1, KEY_VIEW);
         if (IS_ERR(key)) {
+                /* viewing a key under construction is permitted if we have the
+                 * authorisation token handy */
+                if (PTR_ERR(key) == -EACCES) {
+                        instkey = key_get_instantiation_authkey(keyid);
+                        if (!IS_ERR(instkey)) {
+                                key_put(instkey);
+                                key = lookup_user_key(NULL, keyid, 0, 1, 0);
+                                if (!IS_ERR(key))
+                                        goto okay;
+                        }
+                }
+
                 ret = PTR_ERR(key);
                 goto error;
         }
 
+okay:
         /* calculate how much description we're going to return */
         ret = -ENOMEM;
         tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
@@ -568,7 +580,7 @@ long keyctl_keyring_search(key_serial_t ringid,
                 goto error2;
 
         /* get the keyring at which to begin the search */
-        keyring = lookup_user_key(ringid, 0, 0, KEY_SEARCH);
+        keyring = lookup_user_key(NULL, ringid, 0, 0, KEY_SEARCH);
         if (IS_ERR(keyring)) {
                 ret = PTR_ERR(keyring);
                 goto error2;
@@ -577,7 +589,7 @@ long keyctl_keyring_search(key_serial_t ringid,
         /* get the destination keyring if specified */
         dest = NULL;
         if (destringid) {
-                dest = lookup_user_key(destringid, 1, 0, KEY_WRITE);
+                dest = lookup_user_key(NULL, destringid, 1, 0, KEY_WRITE);
                 if (IS_ERR(dest)) {
                         ret = PTR_ERR(dest);
                         goto error3;
@@ -656,24 +668,23 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
         long ret;
 
         /* find the key first */
-        key = lookup_user_key(keyid, 0, 0, 0);
+        key = lookup_user_key(NULL, keyid, 0, 0, 0);
         if (!IS_ERR(key)) {
                 /* see if we can read it directly */
                 if (key_permission(key, KEY_READ))
                         goto can_read_key;
 
-                /* can't; see if it's searchable from this process's
-                 * keyrings */
-                ret = -ENOKEY;
-                if (key_permission(key, KEY_SEARCH)) {
-                        /* okay - we do have search permission on the key
-                         * itself, but do we have the key? */
-                        skey = search_process_keyrings_aux(key->type, key,
-                                                           keyctl_read_key_same);
-                        if (!IS_ERR(skey))
-                                goto can_read_key2;
-                }
-
+                /* we can't; see if it's searchable from this process's
+                 * keyrings
+                 * - we automatically take account of the fact that it may be
+                 *   dangling off an instantiation key
+                 */
+                skey = search_process_keyrings(key->type, key,
+                                               keyctl_read_key_same, current);
+                if (!IS_ERR(skey))
+                        goto can_read_key2;
+
+                ret = PTR_ERR(skey);
                 goto error2;
         }
 
@@ -719,7 +730,7 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
         if (uid == (uid_t) -1 && gid == (gid_t) -1)
                 goto error;
 
-        key = lookup_user_key(id, 1, 1, 0);
+        key = lookup_user_key(NULL, id, 1, 1, 0);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error;
@@ -776,7 +787,7 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
         if (perm & ~(KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
                 goto error;
 
-        key = lookup_user_key(id, 1, 1, 0);
+        key = lookup_user_key(NULL, id, 1, 1, 0);
         if (IS_ERR(key)) {
                 ret = PTR_ERR(key);
                 goto error;
@@ -809,7 +820,8 @@ long keyctl_instantiate_key(key_serial_t id,
                             size_t plen,
                             key_serial_t ringid)
 {
-        struct key *key, *keyring;
+        struct request_key_auth *rka;
+        struct key *instkey, *keyring;
         void *payload;
         long ret;
 
@@ -831,18 +843,21 @@ long keyctl_instantiate_key(key_serial_t id,
                         goto error2;
         }
 
-        /* find the target key (which must be writable) */
-        key = lookup_user_key(id, 0, 1, KEY_WRITE);
-        if (IS_ERR(key)) {
-                ret = PTR_ERR(key);
+        /* find the instantiation authorisation key */
+        instkey = key_get_instantiation_authkey(id);
+        if (IS_ERR(instkey)) {
+                ret = PTR_ERR(instkey);
                 goto error2;
         }
 
-        /* find the destination keyring if present (which must also be
-         * writable) */
+        rka = instkey->payload.data;
+
+        /* find the destination keyring amongst those belonging to the
+         * requesting task */
         keyring = NULL;
         if (ringid) {
-                keyring = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+                keyring = lookup_user_key(rka->context, ringid, 1, 0,
+                                          KEY_WRITE);
                 if (IS_ERR(keyring)) {
                         ret = PTR_ERR(keyring);
                         goto error3;
@@ -850,11 +865,12 @@ long keyctl_instantiate_key(key_serial_t id,
         }
 
         /* instantiate the key and link it into a keyring */
-        ret = key_instantiate_and_link(key, payload, plen, keyring);
+        ret = key_instantiate_and_link(rka->target_key, payload, plen,
+                                       keyring, instkey);
 
         key_put(keyring);
  error3:
-        key_put(key);
+        key_put(instkey);
  error2:
         kfree(payload);
  error:
@@ -869,21 +885,24 @@ long keyctl_instantiate_key(key_serial_t id,
  */
 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
 {
-        struct key *key, *keyring;
+        struct request_key_auth *rka;
+        struct key *instkey, *keyring;
         long ret;
 
-        /* find the target key (which must be writable) */
-        key = lookup_user_key(id, 0, 1, KEY_WRITE);
-        if (IS_ERR(key)) {
-                ret = PTR_ERR(key);
+        /* find the instantiation authorisation key */
+        instkey = key_get_instantiation_authkey(id);
+        if (IS_ERR(instkey)) {
+                ret = PTR_ERR(instkey);
                 goto error;
         }
 
+        rka = instkey->payload.data;
+
         /* find the destination keyring if present (which must also be
          * writable) */
         keyring = NULL;
         if (ringid) {
-                keyring = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+                keyring = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
                 if (IS_ERR(keyring)) {
                         ret = PTR_ERR(keyring);
                         goto error2;
@@ -891,11 +910,11 @@ long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
         }
 
         /* instantiate the key and link it into a keyring */
-        ret = key_negate_and_link(key, timeout, keyring);
+        ret = key_negate_and_link(rka->target_key, timeout, keyring, instkey);
 
         key_put(keyring);
  error2:
-        key_put(key);
+        key_put(instkey);
  error:
         return ret;
 
@@ -903,6 +922,44 @@ long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
 
 /*****************************************************************************/
 /*
+ * set the default keyring in which request_key() will cache keys
+ * - return the old setting
+ */
+long keyctl_set_reqkey_keyring(int reqkey_defl)
+{
+        int ret;
+
+        switch (reqkey_defl) {
+        case KEY_REQKEY_DEFL_THREAD_KEYRING:
+                ret = install_thread_keyring(current);
+                if (ret < 0)
+                        return ret;
+                goto set;
+
+        case KEY_REQKEY_DEFL_PROCESS_KEYRING:
+                ret = install_process_keyring(current);
+                if (ret < 0)
+                        return ret;
+
+        case KEY_REQKEY_DEFL_DEFAULT:
+        case KEY_REQKEY_DEFL_SESSION_KEYRING:
+        case KEY_REQKEY_DEFL_USER_KEYRING:
+        case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
+        set:
+                current->jit_keyring = reqkey_defl;
+
+        case KEY_REQKEY_DEFL_NO_CHANGE:
+                return current->jit_keyring;
+
+        case KEY_REQKEY_DEFL_GROUP_KEYRING:
+        default:
+                return -EINVAL;
+        }
+
+} /* end keyctl_set_reqkey_keyring() */
+
+/*****************************************************************************/
+/*
  * the key control system call
  */
 asmlinkage long sys_keyctl(int option, unsigned long arg2, unsigned long arg3,
@@ -971,6 +1028,9 @@ asmlinkage long sys_keyctl(int option, unsigned long arg2, unsigned long arg3,
                                          (unsigned) arg3,
                                          (key_serial_t) arg4);
 
+        case KEYCTL_SET_REQKEY_KEYRING:
+                return keyctl_set_reqkey_keyring(arg2);
+
         default:
                 return -EOPNOTSUPP;
         }