diff options
Diffstat (limited to 'security/keys/keyring.c')
| -rw-r--r-- | security/keys/keyring.c | 895 |
1 files changed, 895 insertions, 0 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c new file mode 100644 index 0000000..e2ab4f8 --- /dev/null +++ b/security/keys/keyring.c @@ -0,0 +1,895 @@ +/* keyring.c: keyring handling + * + * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/seq_file.h> +#include <linux/err.h> +#include <asm/uaccess.h> +#include "internal.h" + +/* + * when plumbing the depths of the key tree, this sets a hard limit set on how + * deep we're willing to go + */ +#define KEYRING_SEARCH_MAX_DEPTH 6 + +/* + * we keep all named keyrings in a hash to speed looking them up + */ +#define KEYRING_NAME_HASH_SIZE (1 << 5) + +static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE]; +static DEFINE_RWLOCK(keyring_name_lock); + +static inline unsigned keyring_hash(const char *desc) +{ + unsigned bucket = 0; + + for (; *desc; desc++) + bucket += (unsigned char) *desc; + + return bucket & (KEYRING_NAME_HASH_SIZE - 1); +} + +/* + * the keyring type definition + */ +static int keyring_instantiate(struct key *keyring, + const void *data, size_t datalen); +static int keyring_duplicate(struct key *keyring, const struct key *source); +static int keyring_match(const struct key *keyring, const void *criterion); +static void keyring_destroy(struct key *keyring); +static void keyring_describe(const struct key *keyring, struct seq_file *m); +static long keyring_read(const struct key *keyring, + char __user *buffer, size_t buflen); + +struct key_type key_type_keyring = { + .name = "keyring", + .def_datalen = sizeof(struct keyring_list), + .instantiate = keyring_instantiate, + .duplicate = keyring_duplicate, + .match = keyring_match, + .destroy = keyring_destroy, + .describe = keyring_describe, + .read = keyring_read, +}; + +/* + * semaphore to serialise link/link calls to prevent two link calls in parallel + * introducing a cycle + */ +DECLARE_RWSEM(keyring_serialise_link_sem); + +/*****************************************************************************/ +/* + * publish the name of a keyring so that it can be found by name (if it has + * one) + */ +void keyring_publish_name(struct key *keyring) +{ + int bucket; + + if (keyring->description) { + bucket = keyring_hash(keyring->description); + + write_lock(&keyring_name_lock); + + if (!keyring_name_hash[bucket].next) + INIT_LIST_HEAD(&keyring_name_hash[bucket]); + + list_add_tail(&keyring->type_data.link, + &keyring_name_hash[bucket]); + + write_unlock(&keyring_name_lock); + } + +} /* end keyring_publish_name() */ + +/*****************************************************************************/ +/* + * initialise a keyring + * - we object if we were given any data + */ +static int keyring_instantiate(struct key *keyring, + const void *data, size_t datalen) +{ + int ret; + + ret = -EINVAL; + if (datalen == 0) { + /* make the keyring available by name if it has one */ + keyring_publish_name(keyring); + ret = 0; + } + + return ret; + +} /* end keyring_instantiate() */ + +/*****************************************************************************/ +/* + * duplicate the list of subscribed keys from a source keyring into this one + */ +static int keyring_duplicate(struct key *keyring, const struct key *source) +{ + struct keyring_list *sklist, *klist; + unsigned max; + size_t size; + int loop, ret; + + const unsigned limit = + (PAGE_SIZE - sizeof(*klist)) / sizeof(struct key); + + ret = 0; + sklist = source->payload.subscriptions; + + if (sklist && sklist->nkeys > 0) { + max = sklist->nkeys; + BUG_ON(max > limit); + + max = (max + 3) & ~3; + if (max > limit) + max = limit; + + ret = -ENOMEM; + size = sizeof(*klist) + sizeof(struct key) * max; + klist = kmalloc(size, GFP_KERNEL); + if (!klist) + goto error; + + klist->maxkeys = max; + klist->nkeys = sklist->nkeys; + memcpy(klist->keys, + sklist->keys, + sklist->nkeys * sizeof(struct key)); + + for (loop = klist->nkeys - 1; loop >= 0; loop--) + atomic_inc(&klist->keys[loop]->usage); + + keyring->payload.subscriptions = klist; + ret = 0; + } + + error: + return ret; + +} /* end keyring_duplicate() */ + +/*****************************************************************************/ +/* + * match keyrings on their name + */ +static int keyring_match(const struct key *keyring, const void *description) +{ + return keyring->description && + strcmp(keyring->description, description) == 0; + +} /* end keyring_match() */ + +/*****************************************************************************/ +/* + * dispose of the data dangling from the corpse of a keyring + */ +static void keyring_destroy(struct key *keyring) +{ + struct keyring_list *klist; + int loop; + + if (keyring->description) { + write_lock(&keyring_name_lock); + list_del(&keyring->type_data.link); + write_unlock(&keyring_name_lock); + } + + klist = keyring->payload.subscriptions; + if (klist) { + for (loop = klist->nkeys - 1; loop >= 0; loop--) + key_put(klist->keys[loop]); + kfree(klist); + } + +} /* end keyring_destroy() */ + +/*****************************************************************************/ +/* + * describe the keyring + */ +static void keyring_describe(const struct key *keyring, struct seq_file *m) +{ + struct keyring_list *klist; + + if (keyring->description) { + seq_puts(m, keyring->description); + } + else { + seq_puts(m, "[anon]"); + } + + klist = keyring->payload.subscriptions; + if (klist) + seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys); + else + seq_puts(m, ": empty"); + +} /* end keyring_describe() */ + +/*****************************************************************************/ +/* + * read a list of key IDs from the keyring's contents + */ +static long keyring_read(const struct key *keyring, + char __user *buffer, size_t buflen) +{ + struct keyring_list *klist; + struct key *key; + size_t qty, tmp; + int loop, ret; + + ret = 0; + klist = keyring->payload.subscriptions; + + if (klist) { + /* calculate how much data we could return */ + qty = klist->nkeys * sizeof(key_serial_t); + + if (buffer && buflen > 0) { + if (buflen > qty) + buflen = qty; + + /* copy the IDs of the subscribed keys into the + * buffer */ + ret = -EFAULT; + + for (loop = 0; loop < klist->nkeys; loop++) { + key = klist->keys[loop]; + + tmp = sizeof(key_serial_t); + if (tmp > buflen) + tmp = buflen; + + if (copy_to_user(buffer, + &key->serial, + tmp) != 0) + goto error; + + buflen -= tmp; + if (buflen == 0) + break; + buffer += tmp; + } + } + + ret = qty; + } + + error: + return ret; + +} /* end keyring_read() */ + +/*****************************************************************************/ +/* + * allocate a keyring and link into the destination keyring + */ +struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid, + int not_in_quota, struct key *dest) +{ + struct key *keyring; + int ret; + + keyring = key_alloc(&key_type_keyring, description, + uid, gid, KEY_USR_ALL, not_in_quota); + + if (!IS_ERR(keyring)) { + ret = key_instantiate_and_link(keyring, NULL, 0, dest); + if (ret < 0) { + key_put(keyring); + keyring = ERR_PTR(ret); + } + } + + return keyring; + +} /* end keyring_alloc() */ + +/*****************************************************************************/ +/* + * search the supplied keyring tree for a key that matches the criterion + * - perform a breadth-then-depth search up to the prescribed limit + * - we only find keys on which we have search permission + * - we use the supplied match function to see if the description (or other + * feature of interest) matches + * - we readlock the keyrings as we search down the tree + * - we return -EAGAIN if we didn't find any matching key + * - we return -ENOKEY if we only found negative matching keys + */ +struct key *keyring_search_aux(struct key *keyring, + struct key_type *type, + const void *description, + key_match_func_t match) +{ + struct { + struct key *keyring; + int kix; + } stack[KEYRING_SEARCH_MAX_DEPTH]; + + struct keyring_list *keylist; + struct timespec now; + struct key *key; + long err; + int sp, psp, kix; + + key_check(keyring); + + /* top keyring must have search permission to begin the search */ + key = ERR_PTR(-EACCES); + if (!key_permission(keyring, KEY_SEARCH)) + goto error; + + key = ERR_PTR(-ENOTDIR); + if (keyring->type != &key_type_keyring) + goto error; + + now = current_kernel_time(); + err = -EAGAIN; + sp = 0; + + /* start processing a new keyring */ + descend: + read_lock(&keyring->lock); + if (keyring->flags & KEY_FLAG_REVOKED) + goto not_this_keyring; + + keylist = keyring->payload.subscriptions; + if (!keylist) + goto not_this_keyring; + + /* iterate through the keys in this keyring first */ + for (kix = 0; kix < keylist->nkeys; kix++) { + key = keylist->keys[kix]; + + /* ignore keys not of this type */ + if (key->type != type) + continue; + + /* skip revoked keys and expired keys */ + if (key->flags & KEY_FLAG_REVOKED) + continue; + + if (key->expiry && now.tv_sec >= key->expiry) + continue; + + /* keys that don't match */ + if (!match(key, description)) + continue; + + /* key must have search permissions */ + if (!key_permission(key, KEY_SEARCH)) + continue; + + /* we set a different error code if we find a negative key */ + if (key->flags & KEY_FLAG_NEGATIVE) { + err = -ENOKEY; + continue; + } + + goto found; + } + + /* search through the keyrings nested in this one */ + kix = 0; + ascend: + while (kix < keylist->nkeys) { + key = keylist->keys[kix]; + if (key->type != &key_type_keyring) + goto next; + + /* recursively search nested keyrings + * - only search keyrings for which we have search permission + */ + if (sp >= KEYRING_SEARCH_MAX_DEPTH) + goto next; + + if (!key_permission(key, KEY_SEARCH)) + goto next; + + /* evade loops in the keyring tree */ + for (psp = 0; psp < sp; psp++) + if (stack[psp].keyring == keyring) + goto next; + + /* stack the current position */ + stack[sp].keyring = keyring; + stack[sp].kix = kix; + sp++; + + /* begin again with the new keyring */ + keyring = key; + goto descend; + + next: + kix++; + } + + /* the keyring we're looking at was disqualified or didn't contain a + * matching key */ + not_this_keyring: + read_unlock(&keyring->lock); + + if (sp > 0) { + /* resume the processing of a keyring higher up in the tree */ + sp--; + keyring = stack[sp].keyring; + keylist = keyring->payload.subscriptions; + kix = stack[sp].kix + 1; + goto ascend; + } + + key = ERR_PTR(err); + goto error; + + /* we found a viable match */ + found: + atomic_inc(&key->usage); + read_unlock(&keyring->lock); + + /* unwind the keyring stack */ + while (sp > 0) { + sp--; + read_unlock(&stack[sp].keyring->lock); + } + + key_check(key); + error: + return key; + +} /* end keyring_search_aux() */ + +/*****************************************************************************/ +/* + * search the supplied keyring tree for a key that matches the criterion + * - perform a breadth-then-depth search up to the prescribed limit + * - we only find keys on which we have search permission + * - we readlock the keyrings as we search down the tree + * - we return -EAGAIN if we didn't find any matching key + * - we return -ENOKEY if we only found negative matching keys + */ +struct key *keyring_search(struct key *keyring, + struct key_type *type, + const char *description) +{ + return keyring_search_aux(keyring, type, description, type->match); + +} /* end keyring_search() */ + +EXPORT_SYMBOL(keyring_search); + +/*****************************************************************************/ +/* + * search the given keyring only (no recursion) + * - keyring must be locked by caller + */ +struct key *__keyring_search_one(struct key *keyring, + const struct key_type *ktype, + const char *description, + key_perm_t perm) +{ + struct keyring_list *klist; + struct key *key; + int loop; + + klist = keyring->payload.subscriptions; + if (klist) { + for (loop = 0; loop < klist->nkeys; loop++) { + key = klist->keys[loop]; + + if (key->type == ktype && + key->type->match(key, description) && + key_permission(key, perm) && + !(key->flags & KEY_FLAG_REVOKED) + ) + goto found; + } + } + + key = ERR_PTR(-ENOKEY); + goto error; + + found: + atomic_inc(&key->usage); + error: + return key; + +} /* end __keyring_search_one() */ + +/*****************************************************************************/ +/* + * find a keyring with the specified name + * - all named keyrings are searched + * - only find keyrings with search permission for the process + * - only find keyrings with a serial number greater than the one specified + */ +struct key *find_keyring_by_name(const char *name, key_serial_t bound) +{ + struct key *keyring; + int bucket; + + keyring = ERR_PTR(-EINVAL); + if (!name) + goto error; + + bucket = keyring_hash(name); + + read_lock(&keyring_name_lock); + + if (keyring_name_hash[bucket].next) { + /* search this hash bucket for a keyring with a matching name + * that's readable and that hasn't been revoked */ + list_for_each_entry(keyring, + &keyring_name_hash[bucket], + type_data.link + ) { + if (keyring->flags & KEY_FLAG_REVOKED) + continue; + + if (strcmp(keyring->description, name) != 0) + continue; + + if (!key_permission(keyring, KEY_SEARCH)) + continue; + + /* found a potential candidate, but we still need to + * check the serial number */ + if (keyring->serial <= bound) + continue; + + /* we've got a match */ + atomic_inc(&keyring->usage); + read_unlock(&keyring_name_lock); + goto error; + } + } + + read_unlock(&keyring_name_lock); + keyring = ERR_PTR(-ENOKEY); + + error: + return keyring; + +} /* end find_keyring_by_name() */ + +/*****************************************************************************/ +/* + * see if a cycle will will be created by inserting acyclic tree B in acyclic + * tree A at the topmost level (ie: as a direct child of A) + * - since we are adding B to A at the top level, checking for cycles should + * just be a matter of seeing if node A is somewhere in tree B + */ +static int keyring_detect_cycle(struct key *A, struct key *B) +{ + struct { + struct key *subtree; + int kix; + } stack[KEYRING_SEARCH_MAX_DEPTH]; + + struct keyring_list *keylist; + struct key *subtree, *key; + int sp, kix, ret; + + ret = -EDEADLK; + if (A == B) + goto error; + + subtree = B; + sp = 0; + + /* start processing a new keyring */ + descend: + read_lock(&subtree->lock); + if (subtree->flags & KEY_FLAG_REVOKED) + goto not_this_keyring; + + keylist = subtree->payload.subscriptions; + if (!keylist) + goto not_this_keyring; + kix = 0; + + ascend: + /* iterate through the remaining keys in this keyring */ + for (; kix < keylist->nkeys; kix++) { + key = keylist->keys[kix]; + + if (key == A) + goto cycle_detected; + + /* recursively check nested keyrings */ + if (key->type == &key_type_keyring) { + if (sp >= KEYRING_SEARCH_MAX_DEPTH) + goto too_deep; + + /* stack the current position */ + stack[sp].subtree = subtree; + stack[sp].kix = kix; + sp++; + + /* begin again with the new keyring */ + subtree = key; + goto descend; + } + } + + /* the keyring we're looking at was disqualified or didn't contain a + * matching key */ + not_this_keyring: + read_unlock(&subtree->lock); + + if (sp > 0) { + /* resume the checking of a keyring higher up in the tree */ + sp--; + subtree = stack[sp].subtree; + keylist = subtree->payload.subscriptions; + kix = stack[sp].kix + 1; + goto ascend; + } + + ret = 0; /* no cycles detected */ + + error: + return ret; + + too_deep: + ret = -ELOOP; + goto error_unwind; + cycle_detected: + ret = -EDEADLK; + error_unwind: + read_unlock(&subtree->lock); + + /* unwind the keyring stack */ + while (sp > 0) { + sp--; + read_unlock(&stack[sp].subtree->lock); + } + + goto error; + +} /* end keyring_detect_cycle() */ + +/*****************************************************************************/ +/* + * link a key into to a keyring + * - must be called with the keyring's semaphore held + */ +int __key_link(struct key *keyring, struct key *key) +{ + struct keyring_list *klist, *nklist; + unsigned max; + size_t size; + int ret; + + ret = -EKEYREVOKED; + if (keyring->flags & KEY_FLAG_REVOKED) + goto error; + + ret = -ENOTDIR; + if (keyring->type != &key_type_keyring) + goto error; + + /* serialise link/link calls to prevent parallel calls causing a + * cycle when applied to two keyring in opposite orders */ + down_write(&keyring_serialise_link_sem); + + /* check that we aren't going to create a cycle adding one keyring to + * another */ + if (key->type == &key_type_keyring) { + ret = keyring_detect_cycle(keyring, key); + if (ret < 0) + goto error2; + } + + /* check that we aren't going to overrun the user's quota */ + ret = key_payload_reserve(keyring, + keyring->datalen + KEYQUOTA_LINK_BYTES); + if (ret < 0) + goto error2; + + klist = keyring->payload.subscriptions; + + if (klist && klist->nkeys < klist->maxkeys) { + /* there's sufficient slack space to add directly */ + atomic_inc(&key->usage); + + write_lock(&keyring->lock); + klist->keys[klist->nkeys++] = key; + write_unlock(&keyring->lock); + + ret = 0; + } + else { + /* grow the key list */ + max = 4; + if (klist) + max += klist->maxkeys; + + ret = -ENFILE; + size = sizeof(*klist) + sizeof(*key) * max; + if (size > PAGE_SIZE) + goto error3; + + ret = -ENOMEM; + nklist = kmalloc(size, GFP_KERNEL); + if (!nklist) + goto error3; + nklist->maxkeys = max; + nklist->nkeys = 0; + + if (klist) { + nklist->nkeys = klist->nkeys; + memcpy(nklist->keys, + klist->keys, + sizeof(struct key *) * klist->nkeys); + } + + /* add the key into the new space */ + atomic_inc(&key->usage); + + write_lock(&keyring->lock); + keyring->payload.subscriptions = nklist; + nklist->keys[nklist->nkeys++] = key; + write_unlock(&keyring->lock); + + /* dispose of the old keyring list */ + kfree(klist); + + ret = 0; + } + + error2: + up_write(&keyring_serialise_link_sem); + error: + return ret; + + error3: + /* undo the quota changes */ + key_payload_reserve(keyring, + keyring->datalen - KEYQUOTA_LINK_BYTES); + goto error2; + +} /* end __key_link() */ + +/*****************************************************************************/ +/* + * link a key to a keyring + */ +int key_link(struct key *keyring, struct key *key) +{ + int ret; + + key_check(keyring); + key_check(key); + + down_write(&keyring->sem); + ret = __key_link(keyring, key); + up_write(&keyring->sem); + + return ret; + +} /* end key_link() */ + +EXPORT_SYMBOL(key_link); + +/*****************************************************************************/ +/* + * unlink the first link to a key from a keyring + */ +int key_unlink(struct key *keyring, struct key *key) +{ + struct keyring_list *klist; + int loop, ret; + + key_check(keyring); + key_check(key); + + ret = -ENOTDIR; + if (keyring->type != &key_type_keyring) + goto error; + + down_write(&keyring->sem); + + klist = keyring->payload.subscriptions; + if (klist) { + /* search the keyring for the key */ + for (loop = 0; loop < klist->nkeys; loop++) + if (klist->keys[loop] == key) + goto key_is_present; + } + + up_write(&keyring->sem); + ret = -ENOENT; + goto error; + + key_is_present: + /* adjust the user's quota */ + key_payload_reserve(keyring, + keyring->datalen - KEYQUOTA_LINK_BYTES); + + /* shuffle down the key pointers + * - it might be worth shrinking the allocated memory, but that runs + * the risk of ENOMEM as we would have to copy + */ + write_lock(&keyring->lock); + + klist->nkeys--; + if (loop < klist->nkeys) + memcpy(&klist->keys[loop], + &klist->keys[loop + 1], + (klist->nkeys - loop) * sizeof(struct key *)); + + write_unlock(&keyring->lock); + + up_write(&keyring->sem); + key_put(key); + ret = 0; + + error: + return ret; + +} /* end key_unlink() */ + +EXPORT_SYMBOL(key_unlink); + +/*****************************************************************************/ +/* + * clear the specified process keyring + * - implements keyctl(KEYCTL_CLEAR) + */ +int keyring_clear(struct key *keyring) +{ + struct keyring_list *klist; + int loop, ret; + + ret = -ENOTDIR; + if (keyring->type == &key_type_keyring) { + /* detach the pointer block with the locks held */ + down_write(&keyring->sem); + + klist = keyring->payload.subscriptions; + if (klist) { + /* adjust the quota */ + key_payload_reserve(keyring, + sizeof(struct keyring_list)); + + write_lock(&keyring->lock); + keyring->payload.subscriptions = NULL; + write_unlock(&keyring->lock); + } + + up_write(&keyring->sem); + + /* free the keys after the locks have been dropped */ + if (klist) { + for (loop = klist->nkeys - 1; loop >= 0; loop--) + key_put(klist->keys[loop]); + + kfree(klist); + } + + ret = 0; + } + + return ret; + +} /* end keyring_clear() */ + +EXPORT_SYMBOL(keyring_clear); |
