Re: [PATCH v11 11/25] LSM: Use lsmblob in security_cred_getsecid

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On 11/13/19 10:19 AM, 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 accommodate multiple possible LSM audit users.
> 
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Reviewed-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> cc: linux-integrity@xxxxxxxxxxxxxxx

Acked-by: John Johansen <john.johansen@xxxxxxxxxxxxx>


> ---
>  include/linux/security.h          |  2 +-
>  kernel/audit.c                    | 19 +++++++-----------
>  kernel/audit.h                    |  5 +++--
>  kernel/auditsc.c                  | 33 +++++++++++--------------------
>  security/integrity/ima/ima_main.c |  8 ++++----
>  security/security.c               | 12 ++++++++---
>  6 files changed, 36 insertions(+), 43 deletions(-)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index a845254fc415..f7bc7aef95cb 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -434,7 +434,7 @@ 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 fd29186ae977..ba9f78e36d1e 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -124,7 +124,7 @@ 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]
> @@ -1416,23 +1416,21 @@ 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(&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);
>  		}
> @@ -2274,7 +2272,6 @@ 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 ||
> @@ -2285,9 +2282,7 @@ 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 6fb7160412d4..af9bc09e656c 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;
> @@ -329,7 +330,7 @@ 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 5752e51883d5..c1e3ac8eb1ad 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;
>  };
> @@ -957,14 +957,14 @@ 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)
> @@ -973,9 +973,8 @@ 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 {
> @@ -1546,7 +1545,7 @@ 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;
>  	}
> @@ -1555,7 +1554,7 @@ 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) {
> @@ -1733,7 +1732,7 @@ 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;
> @@ -2384,15 +2383,12 @@ 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);
>  }
>  
> @@ -2408,7 +2404,6 @@ 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;
> @@ -2420,9 +2415,7 @@ 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;
>  	}
> @@ -2443,9 +2436,7 @@ 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 cac654c2faaf..305a00a6b087 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -408,7 +408,6 @@ int ima_file_mmap(struct file *file, unsigned long prot)
>  int ima_bprm_check(struct linux_binprm *bprm)
>  {
>  	int ret;
> -	u32 secid;
>  	struct lsmblob blob;
>  
>  	security_task_getsecid(current, &blob);
> @@ -418,9 +417,10 @@ 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 bd279a24adfc..3aba440624f9 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1615,10 +1615,16 @@ 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);
>  
> 




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