From 504b69eb3c95180bc59f1ae9096ad4b10bbbf254 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 19 Jun 2019 16:10:15 +0100 Subject: [PATCH] keys: Fix request_key() lack of Link perm check on found key The request_key() syscall allows a process to gain access to the 'possessor' permits of any key that grants it Search permission by virtue of request_key() not checking whether a key it finds grants Link permission to the caller. Signed-off-by: David Howells --- Documentation/security/keys/core.rst | 4 ++++ security/keys/request_key.c | 10 ++++++++++ 2 files changed, 14 insertions(+) diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst index 823d29bf44f7..82dd457ff78d 100644 --- a/Documentation/security/keys/core.rst +++ b/Documentation/security/keys/core.rst @@ -433,6 +433,10 @@ The main syscalls are: /sbin/request-key will be invoked in an attempt to obtain a key. The callout_info string will be passed as an argument to the program. + To link a key into the destination keyring the key must grant link + permission on the key to the caller and the keyring must grant write + permission. + See also Documentation/security/keys/request-key.rst. diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 857da65e1940..a6543ed98b1f 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -564,6 +564,16 @@ struct key *request_key_and_link(struct key_type *type, key_ref = search_process_keyrings(&ctx); if (!IS_ERR(key_ref)) { + if (dest_keyring) { + ret = key_task_permission(key_ref, current_cred(), + KEY_NEED_LINK); + if (ret < 0) { + key_ref_put(key_ref); + key = ERR_PTR(ret); + goto error_free; + } + } + key = key_ref_to_ptr(key_ref); if (dest_keyring) { ret = key_link(dest_keyring, key);