[PATCH] keys: Permit running process to instantiate keys

Make it possible for a running process (such as gssapid) to be able to
instantiate a key, as was requested by Trond Myklebust for NFS4.

The patch makes the following changes:

 (1) A new, optional key type method has been added. This permits a key type
     to intercept requests at the point /sbin/request-key is about to be
     spawned and do something else with them - passing them over the
     rpc_pipefs files or netlink sockets for instance.

     The uninstantiated key, the authorisation key and the intended operation
     name are passed to the method.

 (2) The callout_info is no longer passed as an argument to /sbin/request-key
     to prevent unauthorised viewing of this data using ps or by looking in
     /proc/pid/cmdline.

     This means that the old /sbin/request-key program will not work with the
     patched kernel as it will expect to see an extra argument that is no
     longer there.

     A revised keyutils package will be made available tomorrow.

 (3) The callout_info is now attached to the authorisation key. Reading this
     key will retrieve the information.

 (4) A new field has been added to the task_struct. This holds the
     authorisation key currently active for a thread. Searches now look here
     for the caller's set of keys rather than looking for an auth key in the
     lowest level of the session keyring.

     This permits a thread to be servicing multiple requests at once and to
     switch between them. Note that this is per-thread, not per-process, and
     so is usable in multithreaded programs.

     The setting of this field is inherited across fork and exec.

 (5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that
     permits a thread to assume the authority to deal with an uninstantiated
     key. Assumption is only permitted if the authorisation key associated
     with the uninstantiated key is somewhere in the thread's keyrings.

     This function can also clear the assumption.

 (6) A new magic key specifier has been added to refer to the currently
     assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY).

 (7) Instantiation will only proceed if the appropriate authorisation key is
     assumed first. The assumed authorisation key is discarded if
     instantiation is successful.

 (8) key_validate() is moved from the file of request_key functions to the
     file of permissions functions.

 (9) The documentation is updated.

From: <Valdis.Kletnieks@vt.edu>

    Build fix.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Alexander Zangerl <az@bond.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 117 insertions, 75 deletions

diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index a8e4069d48cb..cce6ba6b0323 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -15,11 +15,13 @@
 #include <linux/sched.h>
 #include <linux/err.h>
 #include <linux/seq_file.h>
+#include <asm/uaccess.h>
 #include "internal.h"
 
 static int request_key_auth_instantiate(struct key *, const void *, size_t);
 static void request_key_auth_describe(const struct key *, struct seq_file *);
 static void request_key_auth_destroy(struct key *);
+static long request_key_auth_read(const struct key *, char __user *, size_t);
 
 /*
  * the request-key authorisation key type definition
@@ -30,51 +32,25 @@ struct key_type key_type_request_key_auth = {
         .instantiate    = request_key_auth_instantiate,
         .describe       = request_key_auth_describe,
         .destroy        = request_key_auth_destroy,
+        .read           = request_key_auth_read,
 };
 
 /*****************************************************************************/
 /*
- * instantiate a request-key authorisation record
+ * instantiate a request-key authorisation key
  */
 static int request_key_auth_instantiate(struct key *key,
                                         const void *data,
                                         size_t datalen)
 {
-        struct request_key_auth *rka, *irka;
-        struct key *instkey;
-        int ret;
-
-        ret = -ENOMEM;
-        rka = kmalloc(sizeof(*rka), GFP_KERNEL);
-        if (rka) {
-                /* see if the calling process is already servicing the key
-                 * request of another process */
-                instkey = key_get_instantiation_authkey(0);
-                if (!IS_ERR(instkey)) {
-                        /* it is - use that instantiation context here too */
-                        irka = instkey->payload.data;
-                        rka->context = irka->context;
-                        rka->pid = irka->pid;
-                        key_put(instkey);
-                }
-                else {
-                        /* it isn't - use this process as the context */
-                        rka->context = current;
-                        rka->pid = current->pid;
-                }
-
-                rka->target_key = key_get((struct key *) data);
-                key->payload.data = rka;
-                ret = 0;
-        }
-
-        return ret;
+        key->payload.data = (struct request_key_auth *) data;
+        return 0;
 
 } /* end request_key_auth_instantiate() */
 
 /*****************************************************************************/
 /*
- *
+ * reading a request-key authorisation key retrieves the callout information
  */
 static void request_key_auth_describe(const struct key *key,
                                       struct seq_file *m)
@@ -83,12 +59,40 @@ static void request_key_auth_describe(const struct key *key,
 
         seq_puts(m, "key:");
         seq_puts(m, key->description);
-        seq_printf(m, " pid:%d", rka->pid);
+        seq_printf(m, " pid:%d ci:%zu", rka->pid, strlen(rka->callout_info));
 
 } /* end request_key_auth_describe() */
 
 /*****************************************************************************/
 /*
+ * read the callout_info data
+ * - the key's semaphore is read-locked
+ */
+static long request_key_auth_read(const struct key *key,
+                                  char __user *buffer, size_t buflen)
+{
+        struct request_key_auth *rka = key->payload.data;
+        size_t datalen;
+        long ret;
+
+        datalen = strlen(rka->callout_info);
+        ret = datalen;
+
+        /* we can return the data as is */
+        if (buffer && buflen > 0) {
+                if (buflen > datalen)
+                        buflen = datalen;
+
+                if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
+                        ret = -EFAULT;
+        }
+
+        return ret;
+
+} /* end request_key_auth_read() */
+
+/*****************************************************************************/
+/*
  * destroy an instantiation authorisation token key
  */
 static void request_key_auth_destroy(struct key *key)
@@ -104,56 +108,89 @@ static void request_key_auth_destroy(struct key *key)
 
 /*****************************************************************************/
 /*
- * create a session keyring to be for the invokation of /sbin/request-key and
- * stick an authorisation token in it
+ * create an authorisation token for /sbin/request-key or whoever to gain
+ * access to the caller's security data
  */
-struct key *request_key_auth_new(struct key *target, struct key **_rkakey)
+struct key *request_key_auth_new(struct key *target, const char *callout_info)
 {
-        struct key *keyring, *rkakey = NULL;
+        struct request_key_auth *rka, *irka;
+        struct key *authkey = NULL;
         char desc[20];
         int ret;
 
         kenter("%d,", target->serial);
 
-        /* allocate a new session keyring */
-        sprintf(desc, "_req.%u", target->serial);
+        /* allocate a auth record */
+        rka = kmalloc(sizeof(*rka), GFP_KERNEL);
+        if (!rka) {
+                kleave(" = -ENOMEM");
+                return ERR_PTR(-ENOMEM);
+        }
 
-        keyring = keyring_alloc(desc, current->fsuid, current->fsgid, 1, NULL);
-        if (IS_ERR(keyring)) {
-                kleave("= %ld", PTR_ERR(keyring));
-                return keyring;
+        /* see if the calling process is already servicing the key request of
+         * another process */
+        if (current->request_key_auth) {
+                /* it is - use that instantiation context here too */
+                irka = current->request_key_auth->payload.data;
+                rka->context = irka->context;
+                rka->pid = irka->pid;
         }
+        else {
+                /* it isn't - use this process as the context */
+                rka->context = current;
+                rka->pid = current->pid;
+        }
+
+        rka->target_key = key_get(target);
+        rka->callout_info = callout_info;
 
         /* allocate the auth key */
         sprintf(desc, "%x", target->serial);
 
-        rkakey = key_alloc(&key_type_request_key_auth, desc,
-                           current->fsuid, current->fsgid,
-                           KEY_POS_VIEW | KEY_USR_VIEW, 1);
-        if (IS_ERR(rkakey)) {
-                key_put(keyring);
-                kleave("= %ld", PTR_ERR(rkakey));
-                return rkakey;
+        authkey = key_alloc(&key_type_request_key_auth, desc,
+                            current->fsuid, current->fsgid,
+                            KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
+                            KEY_USR_VIEW, 1);
+        if (IS_ERR(authkey)) {
+                ret = PTR_ERR(authkey);
+                goto error_alloc;
         }
 
         /* construct and attach to the keyring */
-        ret = key_instantiate_and_link(rkakey, target, 0, keyring, NULL);
-        if (ret < 0) {
-                key_revoke(rkakey);
-                key_put(rkakey);
-                key_put(keyring);
-                kleave("= %d", ret);
-                return ERR_PTR(ret);
-        }
+        ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
+        if (ret < 0)
+                goto error_inst;
 
-        *_rkakey = rkakey;
-        kleave(" = {%d} ({%d})", keyring->serial, rkakey->serial);
-        return keyring;
+        kleave(" = {%d})", authkey->serial);
+        return authkey;
+
+error_inst:
+        key_revoke(authkey);
+        key_put(authkey);
+error_alloc:
+        key_put(rka->target_key);
+        kfree(rka);
+        kleave("= %d", ret);
+        return ERR_PTR(ret);
 
 } /* end request_key_auth_new() */
 
 /*****************************************************************************/
 /*
+ * see if an authorisation key is associated with a particular key
+ */
+static int key_get_instantiation_authkey_match(const struct key *key,
+                                               const void *_id)
+{
+        struct request_key_auth *rka = key->payload.data;
+        key_serial_t id = (key_serial_t)(unsigned long) _id;
+
+        return rka->target_key->serial == id;
+
+} /* end key_get_instantiation_authkey_match() */
+
+/*****************************************************************************/
+/*
  * get the authorisation key for instantiation of a specific key if attached to
  * the current process's keyrings
  * - this key is inserted into a keyring and that is set as /sbin/request-key's
@@ -162,22 +199,27 @@ struct key *request_key_auth_new(struct key *target, struct key **_rkakey)
  */
 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 {
-        struct task_struct *tsk = current;
-        struct key *instkey;
-
-        /* we must have our own personal session keyring */
-        if (!tsk->signal->session_keyring)
-                return ERR_PTR(-EACCES);
-
-        /* and it must contain a suitable request authorisation key
-         * - lock RCU against session keyring changing
-         */
-        rcu_read_lock();
+        struct key *authkey;
+        key_ref_t authkey_ref;
+
+        authkey_ref = search_process_keyrings(
+                &key_type_request_key_auth,
+                (void *) (unsigned long) target_id,
+                key_get_instantiation_authkey_match,
+                current);
+
+        if (IS_ERR(authkey_ref)) {
+                authkey = ERR_PTR(PTR_ERR(authkey_ref));
+                goto error;
+        }
 
-        instkey = keyring_search_instkey(
-                rcu_dereference(tsk->signal->session_keyring), target_id);
+        authkey = key_ref_to_ptr(authkey_ref);
+        if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
+                key_put(authkey);
+                authkey = ERR_PTR(-EKEYREVOKED);
+        }
 
-        rcu_read_unlock();
-        return instkey;
+error:
+        return authkey;
 
 } /* end key_get_instantiation_authkey() */