[PATCH 1/2] security: Add a cred_getsecid hook
Matthew Garrett
mjg59 at google.com
Mon Oct 16 20:37:08 UTC 2017
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.
Signed-off-by: Matthew Garrett <mjg59 at google.com>
Cc: Paul Moore <paul at paul-moore.com>
Cc: Stephen Smalley <sds at tycho.nsa.gov>
Cc: Eric Paris <eparis at parisplace.org>
Cc: selinux at tycho.nsa.gov
Cc: Casey Schaufler <casey at schaufler-ca.com>
Cc: linux-security-module at vger.kernel.org
Cc: Mimi Zohar <zohar at linux.vnet.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin at gmail.com>
Cc: linux-integrity at vger.kernel.org
---
include/linux/lsm_hooks.h | 6 ++++++
include/linux/security.h | 1 +
security/security.c | 7 +++++++
security/selinux/hooks.c | 8 ++++++++
security/smack/smack.h | 10 ++++++++++
security/smack/smack_lsm.c | 14 ++++++++++++++
6 files changed, 46 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index ce02f76a6188..48a929fd47e6 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -556,6 +556,10 @@
* @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
+ * @p 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.
@@ -1510,6 +1514,7 @@ union security_list_options {
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);
@@ -1783,6 +1788,7 @@ struct security_hook_heads {
struct list_head cred_free;
struct list_head cred_prepare;
struct list_head cred_transfer;
+ struct list_head cred_getsecid;
struct list_head kernel_act_as;
struct list_head kernel_create_files_as;
struct list_head kernel_read_file;
diff --git a/include/linux/security.h b/include/linux/security.h
index 458e24bea2d4..8d969958c25e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -324,6 +324,7 @@ int security_cred_alloc_blank(struct cred *cred, gfp_t gfp);
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/security.c b/security/security.c
index 55b5997e4b72..0f5784880c94 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1009,6 +1009,13 @@ void security_transfer_creds(struct cred *new, const struct cred *old)
call_void_hook(cred_transfer, new, old);
}
+void security_cred_getsecid(const struct cred *c, u32 *secid)
+{
+ *secid = 0;
+ call_void_hook(cred_getsecid, c, secid);
+}
+EXPORT_SYMBOL(security_cred_getsecid);
+
int security_kernel_act_as(struct cred *new, u32 secid)
{
return call_int_hook(kernel_act_as, 0, new, secid);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 33fd061305c4..e0828e9130c7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3829,6 +3829,13 @@ static void selinux_cred_transfer(struct cred *new, const struct cred *old)
*tsec = *old_tsec;
}
+static void selinux_cred_getsecid(const struct cred *c, u32 *secid)
+{
+ rcu_read_lock();
+ *secid = cred_sid(c);
+ rcu_read_unlock();
+}
+
/*
* set the security data for a kernel service
* - all the creation contexts are set to unlabelled
@@ -6332,6 +6339,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(cred_free, selinux_cred_free),
LSM_HOOK_INIT(cred_prepare, selinux_cred_prepare),
LSM_HOOK_INIT(cred_transfer, selinux_cred_transfer),
+ LSM_HOOK_INIT(cred_getsecid, selinux_cred_getsecid),
LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as),
LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as),
LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request),
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 6a71fc7831ab..5af7b7e709bc 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -391,6 +391,16 @@ static inline struct smack_known *smk_of_task_struct(const struct task_struct *t
return skp;
}
+static inline struct smack_known *smk_of_cred(const struct cred *c)
+{
+ struct smack_known *skp;
+
+ rcu_read_lock();
+ skp = smk_of_task(c->security);
+ rcu_read_unlock();
+ return skp;
+}
+
/*
* Present a pointer to the forked smack label entry in an task blob.
*/
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 463af86812c7..f1710cf76f7f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2080,6 +2080,19 @@ static void smack_cred_transfer(struct cred *new, const struct cred *old)
/* cbs copy rule list */
}
+/**
+ * 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 = smk_of_cred(c);
+ *secid = skp->smk_secid;
+}
+
/**
* smack_kernel_act_as - Set the subjective context in a set of credentials
* @new: points to the set of credentials to be modified.
@@ -4684,6 +4697,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(cred_free, smack_cred_free),
LSM_HOOK_INIT(cred_prepare, smack_cred_prepare),
LSM_HOOK_INIT(cred_transfer, smack_cred_transfer),
+ LSM_HOOK_INIT(cred_getsecid, smack_cred_getsecid),
LSM_HOOK_INIT(kernel_act_as, smack_kernel_act_as),
LSM_HOOK_INIT(kernel_create_files_as, smack_kernel_create_files_as),
LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
--
2.15.0.rc0.271.g36b669edcc-goog
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