[PATCH v24 12/25] LSM: Use lsmblob in security_cred_getsecid

Casey Schaufler
2021-01-26T18:10:31Z

Change the security_cred_getsecid() interface to fill in a
lsmblob instead of a u32 secid. 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@chromium.org>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-integrity@vger.kernel.org
Cc: linux-audit@redhat.com
---
include/linux/security.h | 2 +-
kernel/audit.c | 25 +++++++----------------
kernel/audit.h | 3 ++-
kernel/auditsc.c | 33 +++++++++++--------------------
security/integrity/ima/ima_main.c | 8 ++++----
security/security.c | 12 ++++++++---
6 files changed, 35 insertions(+), 48 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index e8d73b0220e4..e4a4816f1b94 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -468,7 +468,7 @@ 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);
+void security_cred_getsecid(const struct cred *c, struct lsmblob *blob);
int security_kernel_act_as(struct cred *new, struct lsmblob *blob);
int security_kernel_create_files_as(struct cred *new, struct inode *inode);
int security_kernel_module_request(char *kmod_name);
diff --git a/kernel/audit.c b/kernel/audit.c
index e70bbd6b91c4..f6af7b27a6fa 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -125,7 +125,7 @@ static u32 audit_backlog_wait_time = AUDIT_BACKLOG_WAIT_TIME;
/* The identity of the user shutting down the audit system. */
static kuid_t audit_sig_uid = INVALID_UID;
static pid_t audit_sig_pid = -1;
-static u32 audit_sig_sid;
+struct lsmblob audit_sig_lsm;

/* Records can be lost in several ways:
0) [suppressed in audit_alloc]
@@ -1441,29 +1441,21 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
}
case AUDIT_SIGNAL_INFO:
len = 0;
- if (audit_sig_sid) {
- struct lsmblob blob;
-
- /*
- * lsmblob_init sets all values in the lsmblob
- * to audit_sig_sid. This is temporary until
- * audit_sig_sid is converted to a lsmblob, which
- * happens later in this patch set.
- */
- lsmblob_init(&blob, audit_sig_sid);
- err = security_secid_to_secctx(&blob, &ctx, &len);
+ if (lsmblob_is_set(&audit_sig_lsm)) {
+ err = security_secid_to_secctx(&audit_sig_lsm, &ctx,
+ &len);
if (err)
return err;
}
sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
if (!sig_data) {
- if (audit_sig_sid)
+ if (lsmblob_is_set(&audit_sig_lsm))
security_release_secctx(ctx, len);
return -ENOMEM;
}
sig_data->uid = from_kuid(&init_user_ns, audit_sig_uid);
sig_data->pid = audit_sig_pid;
- if (audit_sig_sid) {
+ if (lsmblob_is_set(&audit_sig_lsm)) {
memcpy(sig_data->ctx, ctx, len);
security_release_secctx(ctx, len);
}
@@ -2352,7 +2344,6 @@ int audit_set_loginuid(kuid_t loginuid)
int audit_signal_info(int sig, struct task_struct *t)
{
kuid_t uid = current_uid(), auid;
- struct lsmblob blob;

if (auditd_test_task(t) &&
(sig == SIGTERM || sig == SIGHUP ||
@@ -2363,9 +2354,7 @@ int audit_signal_info(int sig, struct task_struct *t)
audit_sig_uid = auid;
else
audit_sig_uid = uid;
- security_task_getsecid(current, &blob);
- /* scaffolding until audit_sig_sid is converted */
- audit_sig_sid = blob.secid[0];
+ security_task_getsecid(current, &audit_sig_lsm);
}

return audit_signal_info_syscall(t);
diff --git a/kernel/audit.h b/kernel/audit.h
index 3b9c0945225a..ce41886807bb 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -9,6 +9,7 @@
#include <linux/fs.h>
#include <linux/audit.h>
#include <linux/skbuff.h>
+#include <linux/security.h>
#include <uapi/linux/mqueue.h>
#include <linux/tty.h>

@@ -134,7 +135,7 @@ struct audit_context {
kuid_t target_auid;
kuid_t target_uid;
unsigned int target_sessionid;
- u32 target_sid;
+ struct lsmblob target_lsm;
char target_comm[TASK_COMM_LEN];

struct audit_tree_refs *trees, *first_trees;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 7883b8ac8ea4..c766502b58f2 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -111,7 +111,7 @@ struct audit_aux_data_pids {
kuid_t target_auid[AUDIT_AUX_PIDS];
kuid_t target_uid[AUDIT_AUX_PIDS];
unsigned int target_sessionid[AUDIT_AUX_PIDS];
- u32 target_sid[AUDIT_AUX_PIDS];
+ struct lsmblob target_lsm[AUDIT_AUX_PIDS];
char target_comm[AUDIT_AUX_PIDS][TASK_COMM_LEN];
int pid_count;
};
@@ -993,14 +993,14 @@ static inline void audit_free_context(struct audit_context *context)
}

static int audit_log_pid_context(struct audit_context *context, pid_t pid,
- kuid_t auid, kuid_t uid, unsigned int sessionid,
- u32 sid, char *comm)
+ kuid_t auid, kuid_t uid,
+ unsigned int sessionid,
+ struct lsmblob *blob, char *comm)
{
struct audit_buffer *ab;
char *ctx = NULL;
u32 len;
int rc = 0;
- struct lsmblob blob;

ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
if (!ab)
@@ -1009,9 +1009,8 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
audit_log_format(ab, "opid=%d oauid=%d ouid=%d oses=%d", pid,
from_kuid(&init_user_ns, auid),
from_kuid(&init_user_ns, uid), sessionid);
- if (sid) {
- lsmblob_init(&blob, sid);
- if (security_secid_to_secctx(&blob, &ctx, &len)) {
+ if (lsmblob_is_set(blob)) {
+ if (security_secid_to_secctx(blob, &ctx, &len)) {
audit_log_format(ab, " obj=(none)");
rc = 1;
} else {
@@ -1582,7 +1581,7 @@ static void audit_log_exit(void)
axs->target_auid[i],
axs->target_uid[i],
axs->target_sessionid[i],
- axs->target_sid[i],
+ &axs->target_lsm[i],
axs->target_comm[i]))
call_panic = 1;
}
@@ -1591,7 +1590,7 @@ static void audit_log_exit(void)
audit_log_pid_context(context, context->target_pid,
context->target_auid, context->target_uid,
context->target_sessionid,
- context->target_sid, context->target_comm))
+ &context->target_lsm, context->target_comm))
call_panic = 1;

if (context->pwd.dentry && context->pwd.mnt) {
@@ -1769,7 +1768,7 @@ void __audit_syscall_exit(int success, long return_code)
context->aux = NULL;
context->aux_pids = NULL;
context->target_pid = 0;
- context->target_sid = 0;
+ lsmblob_init(&context->target_lsm, 0);
context->sockaddr_len = 0;
context->type = 0;
context->fds[0] = -1;
@@ -2421,15 +2420,12 @@ int __audit_sockaddr(int len, void *a)
void __audit_ptrace(struct task_struct *t)
{
struct audit_context *context = audit_context();
- struct lsmblob blob;

context->target_pid = task_tgid_nr(t);
context->target_auid = audit_get_loginuid(t);
context->target_uid = task_uid(t);
context->target_sessionid = audit_get_sessionid(t);
- security_task_getsecid(t, &blob);
- /* scaffolding - until target_sid is converted */
- context->target_sid = blob.secid[0];
+ security_task_getsecid(t, &context->target_lsm);
memcpy(context->target_comm, t->comm, TASK_COMM_LEN);
}

@@ -2445,7 +2441,6 @@ int audit_signal_info_syscall(struct task_struct *t)
struct audit_aux_data_pids *axp;
struct audit_context *ctx = audit_context();
kuid_t t_uid = task_uid(t);
- struct lsmblob blob;

if (!audit_signals || audit_dummy_context())
return 0;
@@ -2457,9 +2452,7 @@ int audit_signal_info_syscall(struct task_struct *t)
ctx->target_auid = audit_get_loginuid(t);
ctx->target_uid = t_uid;
ctx->target_sessionid = audit_get_sessionid(t);
- security_task_getsecid(t, &blob);
- /* scaffolding until target_sid is converted */
- ctx->target_sid = blob.secid[0];
+ security_task_getsecid(t, &ctx->target_lsm);
memcpy(ctx->target_comm, t->comm, TASK_COMM_LEN);
return 0;
}
@@ -2480,9 +2473,7 @@ int audit_signal_info_syscall(struct task_struct *t)
axp->target_auid[axp->pid_count] = audit_get_loginuid(t);
axp->target_uid[axp->pid_count] = t_uid;
axp->target_sessionid[axp->pid_count] = audit_get_sessionid(t);
- security_task_getsecid(t, &blob);
- /* scaffolding until target_sid is converted */
- axp->target_sid[axp->pid_count] = blob.secid[0];
+ security_task_getsecid(t, &axp->target_lsm[axp->pid_count]);
memcpy(axp->target_comm[axp->pid_count], t->comm, TASK_COMM_LEN);
axp->pid_count++;

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 175a79076569..e4ed01b1919a 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -469,7 +469,6 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
int ima_bprm_check(struct linux_binprm *bprm)
{
int ret;
- u32 secid;
struct lsmblob blob;

security_task_getsecid(current, &blob);
@@ -479,9 +478,10 @@ int ima_bprm_check(struct linux_binprm *bprm)
if (ret)
return ret;

- security_cred_getsecid(bprm->cred, &secid);
- return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
- MAY_EXEC, CREDS_CHECK);
+ security_cred_getsecid(bprm->cred, &blob);
+ /* scaffolding until process_measurement changes */
+ return process_measurement(bprm->file, bprm->cred, blob.secid[0],
+ NULL, 0, MAY_EXEC, CREDS_CHECK);
}

/**
diff --git a/security/security.c b/security/security.c
index 9241245a9d4b..45824239cb2f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1739,10 +1739,16 @@ 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)
+void security_cred_getsecid(const struct cred *c, struct lsmblob *blob)
{
- *secid = 0;
- call_void_hook(cred_getsecid, c, secid);
+ struct security_hook_list *hp;
+
+ lsmblob_init(blob, 0);
+ hlist_for_each_entry(hp, &security_hook_heads.cred_getsecid, list) {
+ if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
+ continue;
+ hp->hook.cred_getsecid(c, &blob->secid[hp->lsmid->slot]);
+ }
}
EXPORT_SYMBOL(security_cred_getsecid);

--
2.25.4