[PATCH v2 13/25] LSM: Use lsmblob in security_cred_getsecid

Kees Cook keescook at chromium.org
Wed Jun 19 05:11:08 UTC 2019


On Tue, Jun 18, 2019 at 04:05:39PM -0700, Casey Schaufler wrote:
> 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 accomodate multiple possible LSM audit users.

Cool, cool. I'm digging the clean conversions all the way through this
patch. I didn't see patch 14/25 for some reason, though...

-Kees

> 
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
> ---
>  include/linux/security.h          |  2 +-
>  kernel/audit.c                    | 14 +++++-------
>  kernel/audit.h                    |  5 +++--
>  kernel/auditsc.c                  | 37 +++++++++++--------------------
>  security/integrity/ima/ima_main.c |  6 ++---
>  security/security.c               |  9 +++++---
>  6 files changed, 32 insertions(+), 41 deletions(-)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index b28d4f9c7714..07a239292e02 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -383,7 +383,7 @@ 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 *l);
>  int security_kernel_act_as(struct cred *new, struct lsmblob *l);
>  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 3ab2a1c0ba61..a52f8772477f 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -137,7 +137,7 @@ static u32	audit_backlog_wait_time = AUDIT_BACKLOG_WAIT_TIME;
>  /* The identity of the user shutting down the audit system. */
>  kuid_t		audit_sig_uid = INVALID_UID;
>  pid_t		audit_sig_pid = -1;
> -u32		audit_sig_sid = 0;
> +struct lsmblob	audit_sig_lsm;
>  
>  /* Records can be lost in several ways:
>     0) [suppressed in audit_alloc]
> @@ -1429,23 +1429,21 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>  	}
>  	case AUDIT_SIGNAL_INFO:
>  		len = 0;
> -		if (audit_sig_sid) {
> -			struct lsmblob le;
> -
> -			lsmblob_init(&le, audit_sig_sid);
> -			err = security_secid_to_secctx(&le, &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);
>  		}
> diff --git a/kernel/audit.h b/kernel/audit.h
> index 958d5b8fc1b3..29e29c6f4afb 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -22,6 +22,7 @@
>  #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>
>  
> @@ -147,7 +148,7 @@ 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;
> @@ -338,7 +339,7 @@ extern char *audit_unpack_string(void **bufp, size_t *remain, size_t len);
>  
>  extern pid_t audit_sig_pid;
>  extern kuid_t audit_sig_uid;
> -extern u32 audit_sig_sid;
> +extern struct lsmblob audit_sig_lsm;
>  
>  extern int audit_filter(int msgtype, unsigned int listtype);
>  
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index cdd1dd9e0eec..ebdd7eab9247 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -112,7 +112,7 @@ 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;
>  };
> @@ -937,14 +937,14 @@ 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 *l, char *comm)
>  {
>  	struct audit_buffer *ab;
>  	char *ctx = NULL;
>  	u32 len;
>  	int rc = 0;
> -	struct lsmblob le;
>  
>  	ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
>  	if (!ab)
> @@ -953,9 +953,8 @@ 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(&le, sid);
> -		if (security_secid_to_secctx(&le, &ctx, &len)) {
> +	if (lsmblob_is_set(l)) {
> +		if (security_secid_to_secctx(l, &ctx, &len)) {
>  			audit_log_format(ab, " obj=(none)");
>  			rc = 1;
>  		} else {
> @@ -1525,7 +1524,7 @@ 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;
>  	}
> @@ -1534,7 +1533,7 @@ 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) {
> @@ -1711,7 +1710,7 @@ 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;
> @@ -2365,15 +2364,12 @@ int __audit_sockaddr(int len, void *a)
>  void __audit_ptrace(struct task_struct *t)
>  {
>  	struct audit_context *context = audit_context();
> -	struct lsmblob le;
>  
>  	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, &le);
> -	/* scaffolding - until target_sid is converted */
> -	context->target_sid = le.secid[1];
> +	security_task_getsecid(t, &context->target_lsm);
>  	memcpy(context->target_comm, t->comm, TASK_COMM_LEN);
>  }
>  
> @@ -2390,7 +2386,6 @@ int audit_signal_info(int sig, struct task_struct *t)
>  	struct audit_aux_data_pids *axp;
>  	struct audit_context *ctx = audit_context();
>  	kuid_t uid = current_uid(), auid, t_uid = task_uid(t);
> -	struct lsmblob le;
>  
>  	if (auditd_test_task(t) &&
>  	    (sig == SIGTERM || sig == SIGHUP ||
> @@ -2401,9 +2396,7 @@ int audit_signal_info(int sig, struct task_struct *t)
>  			audit_sig_uid = auid;
>  		else
>  			audit_sig_uid = uid;
> -		security_task_getsecid(current, &le);
> -		/* scaffolding until audit_sig_sid is converted */
> -		audit_sig_sid = le.secid[1];
> +		security_task_getsecid(current, &audit_sig_lsm);
>  	}
>  
>  	if (!audit_signals || audit_dummy_context())
> @@ -2416,9 +2409,7 @@ int audit_signal_info(int sig, 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, &le);
> -		/* scaffolding until target_sid is converted */
> -		ctx->target_sid = le.secid[1];
> +		security_task_getsecid(t, &ctx->target_lsm);
>  		memcpy(ctx->target_comm, t->comm, TASK_COMM_LEN);
>  		return 0;
>  	}
> @@ -2439,9 +2430,7 @@ int audit_signal_info(int sig, 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, &le);
> -	/* scaffolding until target_sid is converted */
> -	axp->target_sid[axp->pid_count] = le.secid[1];
> +	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 99870a6286a9..9959d7cbe42e 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -363,7 +363,6 @@ int ima_file_mmap(struct file *file, unsigned long prot)
>  int ima_bprm_check(struct linux_binprm *bprm)
>  {
>  	int ret;
> -	u32 secid;
>  	struct lsmblob le;
>  
>  	security_task_getsecid(current, &le);
> @@ -373,8 +372,9 @@ 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,
> +	security_cred_getsecid(bprm->cred, &le);
> +	/* scaffolding until process_measurement changes */
> +	return process_measurement(bprm->file, bprm->cred, le.secid[1], NULL, 0,
>  				   MAY_EXEC, CREDS_CHECK);
>  }
>  
> diff --git a/security/security.c b/security/security.c
> index e82994667263..46f6cf21d33c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1638,10 +1638,13 @@ 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)
> +void security_cred_getsecid(const struct cred *c, struct lsmblob *l)
>  {
> -	*secid = 0;
> -	call_void_hook(cred_getsecid, c, secid);
> +	struct security_hook_list *hp;
> +
> +	lsmblob_init(l, 0);
> +	hlist_for_each_entry(hp, &security_hook_heads.cred_getsecid, list)
> +		hp->hook.cred_getsecid(c, &l->secid[hp->slot]);
>  }
>  EXPORT_SYMBOL(security_cred_getsecid);
>  
> -- 
> 2.20.1
> 

-- 
Kees Cook



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