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Message-ID: <20240825190048.13289-11-casey@schaufler-ca.com>
Date: Sun, 25 Aug 2024 12:00:45 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: casey@...aufler-ca.com,
paul@...l-moore.com,
linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org,
serge@...lyn.com,
keescook@...omium.org,
john.johansen@...onical.com,
penguin-kernel@...ove.sakura.ne.jp,
stephen.smalley.work@...il.com,
linux-kernel@...r.kernel.org,
mic@...ikod.net,
linux-integrity@...r.kernel.org,
audit@...r.kernel.org,
Todd Kjos <tkjos@...gle.com>
Subject: [PATCH 10/13] LSM: Create new security_cred_getlsmblob LSM hook
Create a new LSM hook security_cred_getlsmblob() which, like
security_cred_getsecid(), fetches LSM specific attributes from the
cred structure. The associated data elements in the audit sub-system
are changed from a secid to a lsmblob to accommodate multiple possible
LSM audit users.
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: John Johansen <john.johansen@...onical.com>
Acked-by: Stephen Smalley <stephen.smalley.work@...il.com>
Acked-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Cc: linux-integrity@...r.kernel.org
Cc: audit@...r.kernel.org
Cc: Todd Kjos <tkjos@...gle.com>
---
include/linux/lsm_hook_defs.h | 2 ++
include/linux/security.h | 7 +++++++
security/integrity/ima/ima_main.c | 7 ++-----
security/security.c | 15 +++++++++++++++
security/selinux/hooks.c | 8 ++++++++
security/smack/smack_lsm.c | 18 ++++++++++++++++++
6 files changed, 52 insertions(+), 5 deletions(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 4fd508841a6e..4bdd36626633 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -215,6 +215,8 @@ LSM_HOOK(int, 0, cred_prepare, struct cred *new, const struct cred *old,
LSM_HOOK(void, LSM_RET_VOID, cred_transfer, struct cred *new,
const struct cred *old)
LSM_HOOK(void, LSM_RET_VOID, cred_getsecid, const struct cred *c, u32 *secid)
+LSM_HOOK(void, LSM_RET_VOID, cred_getlsmblob, const struct cred *c,
+ struct lsmblob *blob)
LSM_HOOK(int, 0, kernel_act_as, struct cred *new, u32 secid)
LSM_HOOK(int, 0, kernel_create_files_as, struct cred *new, struct inode *inode)
LSM_HOOK(int, 0, kernel_module_request, char *kmod_name)
diff --git a/include/linux/security.h b/include/linux/security.h
index 4fe6f64cc3b4..111c1fc18f25 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -473,6 +473,7 @@ 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);
+void security_cred_getlsmblob(const struct cred *c, struct lsmblob *blob);
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);
@@ -1192,6 +1193,12 @@ static inline void security_cred_getsecid(const struct cred *c, u32 *secid)
*secid = 0;
}
+static inline void security_cred_getlsmblob(const struct cred *c,
+ struct lsmblob *blob)
+{
+ *secid = 0;
+}
+
static inline int security_kernel_act_as(struct cred *cred, u32 secid)
{
return 0;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index d408a700fe6f..8171da96a4a4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -541,8 +541,7 @@ static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
static int ima_bprm_check(struct linux_binprm *bprm)
{
int ret;
- u32 secid;
- struct lsmblob blob = { };
+ struct lsmblob blob;
security_current_getlsmblob_subj(&blob);
ret = process_measurement(bprm->file, current_cred(),
@@ -550,9 +549,7 @@ static int ima_bprm_check(struct linux_binprm *bprm)
if (ret)
return ret;
- security_cred_getsecid(bprm->cred, &secid);
- /* scaffolding */
- blob.scaffold.secid = secid;
+ security_cred_getlsmblob(bprm->cred, &blob);
return process_measurement(bprm->file, bprm->cred, &blob, NULL, 0,
MAY_EXEC, CREDS_CHECK);
}
diff --git a/security/security.c b/security/security.c
index c2be9798c012..325030bc7112 100644
--- a/security/security.c
+++ b/security/security.c
@@ -3153,6 +3153,21 @@ void security_cred_getsecid(const struct cred *c, u32 *secid)
}
EXPORT_SYMBOL(security_cred_getsecid);
+/**
+ * security_cred_getlsmblob() - Get the LSM data from a set of credentials
+ * @c: credentials
+ * @blob: destination for the LSM data
+ *
+ * Retrieve the security data of the cred structure @c. In case of
+ * failure, @blob will be cleared.
+ */
+void security_cred_getlsmblob(const struct cred *c, struct lsmblob *blob)
+{
+ lsmblob_init(blob);
+ call_void_hook(cred_getlsmblob, c, blob);
+}
+EXPORT_SYMBOL(security_cred_getlsmblob);
+
/**
* security_kernel_act_as() - Set the kernel credentials to act as secid
* @new: credentials
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f5d09beeef0f..076511c446bd 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4029,6 +4029,13 @@ static void selinux_cred_getsecid(const struct cred *c, u32 *secid)
*secid = cred_sid(c);
}
+static void selinux_cred_getlsmblob(const struct cred *c, struct lsmblob *blob)
+{
+ blob->selinux.secid = cred_sid(c);
+ /* scaffolding */
+ blob->scaffold.secid = blob->selinux.secid;
+}
+
/*
* set the security data for a kernel service
* - all the creation contexts are set to unlabelled
@@ -7240,6 +7247,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
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(cred_getlsmblob, selinux_cred_getlsmblob),
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_lsm.c b/security/smack/smack_lsm.c
index 8cda7dcf30e1..dbcf1c65da3c 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2150,6 +2150,23 @@ static void smack_cred_getsecid(const struct cred *cred, u32 *secid)
rcu_read_unlock();
}
+/**
+ * smack_cred_getlsmblob - get the Smack label for a creds structure
+ * @cred: the object creds
+ * @blob: where to put the data
+ *
+ * Sets the Smack part of the blob
+ */
+static void smack_cred_getlsmblob(const struct cred *cred,
+ struct lsmblob *blob)
+{
+ rcu_read_lock();
+ blob->smack.skp = smk_of_task(smack_cred(cred));
+ /* scaffolding */
+ blob->scaffold.secid = blob->smack.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.
@@ -5150,6 +5167,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
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(cred_getlsmblob, smack_cred_getlsmblob),
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),
--
2.41.0
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