From 9f6ed2ca257fa8650b876377833e6f14e272848b Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 17 Jan 2012 16:09:11 -0500 Subject: keys: add a "logon" key type For CIFS, we want to be able to store NTLM credentials (aka username and password) in the keyring. We do not, however want to allow users to fetch those keys back out of the keyring since that would be a security risk. Unfortunately, due to the nuances of key permission bits, it's not possible to do this. We need to grant search permissions so the kernel can find these keys, but that also implies permissions to read the payload. Resolve this by adding a new key_type. This key type is essentially the same as key_type_user, but does not define a .read op. This prevents the payload from ever being visible from userspace. This key type also vets the description to ensure that it's "qualified" by checking to ensure that it has a ':' in it that is preceded by other characters. Acked-by: David Howells Signed-off-by: Jeff Layton Signed-off-by: Steve French --- security/keys/user_defined.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) (limited to 'security/keys/user_defined.c') diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c index 69ff52c08e97..6e1a6276649f 100644 --- a/security/keys/user_defined.c +++ b/security/keys/user_defined.c @@ -18,6 +18,8 @@ #include #include "internal.h" +static int logon_vet_description(const char *desc); + /* * user defined keys take an arbitrary string as the description and an * arbitrary blob of data as the payload @@ -35,6 +37,24 @@ struct key_type key_type_user = { EXPORT_SYMBOL_GPL(key_type_user); +/* + * This key type is essentially the same as key_type_user, but it does + * not define a .read op. This is suitable for storing username and + * password pairs in the keyring that you do not want to be readable + * from userspace. + */ +struct key_type key_type_logon = { + .name = "logon", + .instantiate = user_instantiate, + .update = user_update, + .match = user_match, + .revoke = user_revoke, + .destroy = user_destroy, + .describe = user_describe, + .vet_description = logon_vet_description, +}; +EXPORT_SYMBOL_GPL(key_type_logon); + /* * instantiate a user defined key */ @@ -189,3 +209,20 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen) } EXPORT_SYMBOL_GPL(user_read); + +/* Vet the description for a "logon" key */ +static int logon_vet_description(const char *desc) +{ + char *p; + + /* require a "qualified" description string */ + p = strchr(desc, ':'); + if (!p) + return -EINVAL; + + /* also reject description with ':' as first char */ + if (p == desc) + return -EINVAL; + + return 0; +} -- cgit v1.2.3-59-g8ed1b