security: Add a cred_getsecid hook
For IMA purposes, we want to be able to obtain the prepared secid in the
bprm structure before the credentials are committed. Add a cred_getsecid
hook that makes this possible.
Issue: SEC-3292
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Change-Id: I308732c44cf70fc6358620bc125c4651cc960d22
diff --git a/include/linux/security.h b/include/linux/security.h
index 86eb9ee..7fbd09c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -677,6 +677,10 @@
* @new points to the new credentials.
* @old points to the original credentials.
* Transfer data from original creds to new creds
+ * @cred_getsecid:
+ * Retrieve the security identifier of the cred structure @c
+ * @c contains the credentials, secid will be placed into @secid.
+ * In case of failure, @secid will be set to zero.
* @kernel_act_as:
* Set the credentials for a kernel service to act as (subjective context).
* @new points to the credentials to be modified.
@@ -1517,6 +1521,7 @@
int (*cred_prepare)(struct cred *new, const struct cred *old,
gfp_t gfp);
void (*cred_transfer)(struct cred *new, const struct cred *old);
+ void (*cred_getsecid)(const struct cred *c, u32 *secid);
int (*kernel_act_as)(struct cred *new, u32 secid);
int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
int (*kernel_module_request)(char *kmod_name);
@@ -1787,6 +1792,7 @@
void security_cred_free(struct cred *cred);
int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
void security_transfer_creds(struct cred *new, const struct cred *old);
+void security_cred_getsecid(const struct cred *c, u32 *secid);
int security_kernel_act_as(struct cred *new, u32 secid);
int security_kernel_create_files_as(struct cred *new, struct inode *inode);
int security_kernel_module_request(char *kmod_name);
diff --git a/security/capability.c b/security/capability.c
index b2ee5ae..4a5191f 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -400,6 +400,10 @@
{
}
+static void cap_cred_getsecid(const struct cred *c, u32 *secid)
+{
+}
+
static int cap_kernel_act_as(struct cred *new, u32 secid)
{
return 0;
@@ -987,6 +991,7 @@
set_to_cap_if_null(ops, cred_free);
set_to_cap_if_null(ops, cred_prepare);
set_to_cap_if_null(ops, cred_transfer);
+ set_to_cap_if_null(ops, cred_getsecid);
set_to_cap_if_null(ops, kernel_act_as);
set_to_cap_if_null(ops, kernel_create_files_as);
set_to_cap_if_null(ops, kernel_module_request);
diff --git a/security/security.c b/security/security.c
index 1e11bd7..d13534c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -791,6 +791,13 @@
security_ops->cred_transfer(new, old);
}
+void security_cred_getsecid(const struct cred *c, u32 *secid)
+{
+ *secid = 0;
+ security_ops->cred_getsecid(c, secid);
+}
+EXPORT_SYMBOL(security_cred_getsecid);
+
int security_kernel_act_as(struct cred *new, u32 secid)
{
return security_ops->kernel_act_as(new, secid);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 94d45b8..b397241 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3549,6 +3549,11 @@
*tsec = *old_tsec;
}
+static void selinux_cred_getsecid(const struct cred *c, u32 *secid)
+{
+ *secid = cred_sid(c);
+}
+
/*
* set the security data for a kernel service
* - all the creation contexts are set to unlabelled
@@ -5947,6 +5952,7 @@
.cred_free = selinux_cred_free,
.cred_prepare = selinux_cred_prepare,
.cred_transfer = selinux_cred_transfer,
+ .cred_getsecid = selinux_cred_getsecid,
.kernel_act_as = selinux_kernel_act_as,
.kernel_create_files_as = selinux_kernel_create_files_as,
.kernel_module_request = selinux_kernel_module_request,
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 401b584..74a609c 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1464,6 +1464,23 @@
}
/**
+ * smack_cred_getsecid - get the secid corresponding to a creds structure
+ * @c: the object creds
+ * @secid: where to put the result
+ *
+ * Sets the secid to contain a u32 version of the smack label.
+ */
+static void smack_cred_getsecid(const struct cred *c, u32 *secid)
+{
+ struct smack_known *skp;
+
+ rcu_read_lock();
+ skp = smk_of_task(c->security);
+ *secid = skp->smk_secid;
+ rcu_read_unlock();
+}
+
+/**
* smack_kernel_act_as - Set the subjective context in a set of credentials
* @new: points to the set of credentials to be modified.
* @secid: specifies the security ID to be set
@@ -3557,6 +3574,7 @@
.cred_free = smack_cred_free,
.cred_prepare = smack_cred_prepare,
.cred_transfer = smack_cred_transfer,
+ .cred_getsecid = smack_cred_getsecid,
.kernel_act_as = smack_kernel_act_as,
.kernel_create_files_as = smack_kernel_create_files_as,
.task_setpgid = smack_task_setpgid,