From d040e5af380554c23ffe0a034ae5f3e53da93a1d Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Fri, 24 May 2013 09:18:04 -0400 Subject: [PATCH] audit: audit feature to only allow unsetting the loginuid This is a new audit feature which only grants processes with CAP_AUDIT_CONTROL the ability to unset their loginuid. They cannot directly set it from a valid uid to another valid uid. The ability to unset the loginuid is nice because a priviledged task, like that of container creation, can unset the loginuid and then priv is not needed inside the container when a login daemon needs to set the loginuid. Signed-off-by: Eric Paris Signed-off-by: Richard Guy Briggs Signed-off-by: Eric Paris --- include/uapi/linux/audit.h | 3 ++- kernel/audit.c | 3 ++- kernel/auditsc.c | 3 +++ 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h index 9eddf2c..05e5e8f 100644 --- a/include/uapi/linux/audit.h +++ b/include/uapi/linux/audit.h @@ -386,7 +386,8 @@ struct audit_features { __u32 lock; /* which features to lock */ }; -#define AUDIT_LAST_FEATURE -1 +#define AUDIT_FEATURE_ONLY_UNSET_LOGINUID 0 +#define AUDIT_LAST_FEATURE AUDIT_FEATURE_ONLY_UNSET_LOGINUID #define audit_feature_valid(x) ((x) >= 0 && (x) <= AUDIT_LAST_FEATURE) #define AUDIT_FEATURE_TO_MASK(x) (1 << ((x) & 31)) /* mask for __u32 */ diff --git a/kernel/audit.c b/kernel/audit.c index 29ee6a4..fbfa3a7 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -144,7 +144,8 @@ static struct audit_features af = {.vers = AUDIT_FEATURE_VERSION, .features = 0, .lock = 0,}; -static char *audit_feature_names[0] = { +static char *audit_feature_names[1] = { + "only_unset_loginuid", }; diff --git a/kernel/auditsc.c b/kernel/auditsc.c index c75d781..924c0bf 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -1974,6 +1974,9 @@ static int audit_set_loginuid_perm(kuid_t loginuid) /* it is set, you need permission */ if (!capable(CAP_AUDIT_CONTROL)) return -EPERM; + /* reject if this is not an unset and we don't allow that */ + if (is_audit_feature_set(AUDIT_FEATURE_ONLY_UNSET_LOGINUID) && uid_valid(loginuid)) + return -EPERM; return 0; } -- 2.7.4