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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 6/7] keys: Add a keyctl to move a key between keyrings From: David Howells To: keyrings@vger.kernel.org Cc: dhowells@redhat.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 22 May 2019 23:28:45 +0100 Message-ID: <155856412507.10428.15987388402707639951.stgit@warthog.procyon.org.uk> In-Reply-To: <155856408314.10428.17035328117829912815.stgit@warthog.procyon.org.uk> References: <155856408314.10428.17035328117829912815.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Wed, 22 May 2019 22:28:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a keyctl to atomically move a link to a key from one keyring to another. The key must exist in "from" keyring and a flag can be given to cause the operation to fail if there's a matching key already in the "to" keyring. This can be done with: keyctl(KEYCTL_MOVE, key_serial_t key, key_serial_t from_keyring, key_serial_t to_keyring, unsigned int flags); The key being moved must grant Link permission and both keyrings must grant Write permission. flags should be 0 or KEYCTL_MOVE_EXCL, with the latter preventing displacement of a matching key from the "to" keyring. Signed-off-by: David Howells --- include/linux/key.h | 5 ++ include/uapi/linux/keyctl.h | 3 + security/keys/compat.c | 3 + security/keys/internal.h | 1 security/keys/keyctl.c | 55 +++++++++++++++++++++++++++ security/keys/keyring.c | 88 +++++++++++++++++++++++++++++++++++++++++++ 6 files changed, 155 insertions(+) diff --git a/include/linux/key.h b/include/linux/key.h index 1f09aad1c98c..612e1cf84049 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -310,6 +310,11 @@ extern int key_update(key_ref_t key, extern int key_link(struct key *keyring, struct key *key); +extern int key_move(struct key *key, + struct key *from_keyring, + struct key *to_keyring, + unsigned int flags); + extern int key_unlink(struct key *keyring, struct key *key); diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h index f45ee0f69c0c..fd9fb11b312b 100644 --- a/include/uapi/linux/keyctl.h +++ b/include/uapi/linux/keyctl.h @@ -67,6 +67,7 @@ #define KEYCTL_PKEY_SIGN 27 /* Create a public key signature */ #define KEYCTL_PKEY_VERIFY 28 /* Verify a public key signature */ #define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */ +#define KEYCTL_MOVE 30 /* Move keys between keyrings */ /* keyctl structures */ struct keyctl_dh_params { @@ -112,4 +113,6 @@ struct keyctl_pkey_params { __u32 __spare[7]; }; +#define KEYCTL_MOVE_EXCL 0x00000001 /* Do not displace from the to-keyring */ + #endif /* _LINUX_KEYCTL_H */ diff --git a/security/keys/compat.c b/security/keys/compat.c index 9482df601dc3..b326bc4f84d7 100644 --- a/security/keys/compat.c +++ b/security/keys/compat.c @@ -159,6 +159,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option, return keyctl_pkey_verify(compat_ptr(arg2), compat_ptr(arg3), compat_ptr(arg4), compat_ptr(arg5)); + case KEYCTL_MOVE: + return keyctl_keyring_move(arg2, arg3, arg4, arg5); + default: return -EOPNOTSUPP; } diff --git a/security/keys/internal.h b/security/keys/internal.h index 93513667ff9a..821819b4ee13 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -215,6 +215,7 @@ extern long keyctl_update_key(key_serial_t, const void __user *, size_t); extern long keyctl_revoke_key(key_serial_t); extern long keyctl_keyring_clear(key_serial_t); extern long keyctl_keyring_link(key_serial_t, key_serial_t); +extern long keyctl_keyring_move(key_serial_t, key_serial_t, key_serial_t, unsigned int); extern long keyctl_keyring_unlink(key_serial_t, key_serial_t); extern long keyctl_describe_key(key_serial_t, char __user *, size_t); extern long keyctl_keyring_search(key_serial_t, const char __user *, diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 0f947bcbad46..46188cda177e 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -572,6 +572,55 @@ long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid) return ret; } +/* + * Move a link to a key from one keyring to another, displacing any matching + * key from the destination keyring. + * + * The key must grant the caller Link permission and both keyrings must grant + * the caller Write permission. There must also be a link in the from keyring + * to the key. If both keyrings are the same, nothing is done. + * + * If successful, 0 will be returned. + */ +long keyctl_keyring_move(key_serial_t id, key_serial_t from_ringid, + key_serial_t to_ringid, unsigned int flags) +{ + key_ref_t key_ref, from_ref, to_ref; + long ret; + + if (flags & ~KEYCTL_MOVE_EXCL) + return -EINVAL; + + key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK); + if (IS_ERR(key_ref)) { + ret = PTR_ERR(key_ref); + goto error; + } + + from_ref = lookup_user_key(from_ringid, 0, KEY_NEED_WRITE); + if (IS_ERR(from_ref)) { + ret = PTR_ERR(from_ref); + goto error2; + } + + to_ref = lookup_user_key(to_ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE); + if (IS_ERR(to_ref)) { + ret = PTR_ERR(to_ref); + goto error3; + } + + ret = key_move(key_ref_to_ptr(key_ref), key_ref_to_ptr(from_ref), + key_ref_to_ptr(to_ref), flags); + + key_ref_put(to_ref); +error3: + key_ref_put(from_ref); +error2: + key_ref_put(key_ref); +error: + return ret; +} + /* * Return a description of a key to userspace. * @@ -1772,6 +1821,12 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3, (const void __user *)arg4, (const void __user *)arg5); + case KEYCTL_MOVE: + return keyctl_keyring_move((key_serial_t)arg2, + (key_serial_t)arg3, + (key_serial_t)arg4, + (unsigned int)arg5); + default: return -EOPNOTSUPP; } diff --git a/security/keys/keyring.c b/security/keys/keyring.c index cd669f758632..df3144f9c1aa 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1476,6 +1476,94 @@ int key_unlink(struct key *keyring, struct key *key) } EXPORT_SYMBOL(key_unlink); +/** + * key_move - Move a key from one keyring to another + * @key: The key to move + * @from_keyring: The keyring to remove the link from. + * @to_keyring: The keyring to make the link in. + * @flags: Qualifying flags, such as KEYCTL_MOVE_EXCL. + * + * Make a link in @to_keyring to a key, such that the keyring holds a reference + * on that key and the key can potentially be found by searching that keyring + * whilst simultaneously removing a link to the key from @from_keyring. + * + * This function will write-lock both keyring's semaphores and will consume + * some of the user's key data quota to hold the link on @to_keyring. + * + * Returns 0 if successful, -ENOTDIR if either keyring isn't a keyring, + * -EKEYREVOKED if either keyring has been revoked, -ENFILE if the second + * keyring is full, -EDQUOT if there is insufficient key data quota remaining + * to add another link or -ENOMEM if there's insufficient memory. If + * KEYCTL_MOVE_EXCL is set, then -EEXIST will be returned if there's already a + * matching key in @to_keyring. + * + * It is assumed that the caller has checked that it is permitted for a link to + * be made (the keyring should have Write permission and the key Link + * permission). + */ +int key_move(struct key *key, + struct key *from_keyring, + struct key *to_keyring, + unsigned int flags) +{ + struct assoc_array_edit *from_edit, *to_edit; + int ret; + + kenter("%d,%d,%d", key->serial, from_keyring->serial, to_keyring->serial); + + if (from_keyring == to_keyring) + return 0; + + key_check(key); + key_check(from_keyring); + key_check(to_keyring); + + /* We have to be very careful here to take the keyring locks in the + * right order, lest we open ourselves to deadlocking against another + * move operation. + */ + if (from_keyring < to_keyring) { + ret = __key_unlink_begin(from_keyring, 0, key, &from_edit); + if (ret < 0) + goto out; + ret = __key_link_begin(to_keyring, 1, &key->index_key, &to_edit); + if (ret < 0) { + assoc_array_cancel_edit(from_edit); + goto out; + } + } else { + ret = __key_link_begin(to_keyring, 0, &key->index_key, &to_edit); + if (ret < 0) + goto out; + ret = __key_unlink_begin(from_keyring, 1, key, &from_edit); + if (ret < 0) { + __key_link_end(to_keyring, &key->index_key, to_edit); + goto out; + } + } + + ret = -EEXIST; + if (to_edit->dead_leaf && (flags & KEYCTL_MOVE_EXCL)) + goto error; + + ret = __key_link_check_restriction(to_keyring, key); + if (ret < 0) + goto error; + ret = __key_link_check_live_key(to_keyring, key); + if (ret < 0) + goto error; + + __key_unlink(from_keyring, key, &from_edit); + __key_link(key, &to_edit); +error: + __key_unlink_end(from_keyring, key, from_edit); + __key_link_end(to_keyring, &key->index_key, to_edit); +out: + kleave(" = %d", ret); + return ret; +} +EXPORT_SYMBOL(key_move); + /** * keyring_clear - Clear a keyring * @keyring: The keyring to clear.