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Commit a51d9eaa authored by Kees Cook's avatar Kees Cook Committed by Al Viro
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fs: add link restriction audit reporting 



Adds audit messages for unexpected link restriction violations so that
system owners will have some sort of potentially actionable information
about misbehaving processes.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 800179c9

fs/namei.c

+2 −0
Original line number Diff line number Diff line
@@ -692,6 +692,7 @@ static inline int may_follow_link(struct path *link, struct nameidata *nd) 


	path_put_conditional(link, nd);

	path_put(&nd->path);

	audit_log_link_denied("follow_link", link);

	return -EACCES;

}
@@ -760,6 +761,7 @@ static int may_linkat(struct path *link) 
	    capable(CAP_FOWNER))

		return 0;



	audit_log_link_denied("linkat", link);

	return -EPERM;

}

include/linux/audit.h

+4 −0
Original line number Diff line number Diff line
@@ -130,6 +130,7 @@ 
#define AUDIT_LAST_KERN_ANOM_MSG    1799

#define AUDIT_ANOM_PROMISCUOUS      1700 /* Device changed promiscuous mode */

#define AUDIT_ANOM_ABEND            1701 /* Process ended abnormally */

#define AUDIT_ANOM_LINK		    1702 /* Suspicious use of file links */

#define AUDIT_INTEGRITY_DATA	    1800 /* Data integrity verification */

#define AUDIT_INTEGRITY_METADATA    1801 /* Metadata integrity verification */

#define AUDIT_INTEGRITY_STATUS	    1802 /* Integrity enable status */
@@ -687,6 +688,8 @@ extern void audit_log_d_path(struct audit_buffer *ab, 
					     const struct path *path);

extern void		    audit_log_key(struct audit_buffer *ab,

					  char *key);

extern void		    audit_log_link_denied(const char *operation,

						  struct path *link);

extern void		    audit_log_lost(const char *message);

#ifdef CONFIG_SECURITY

extern void 		    audit_log_secctx(struct audit_buffer *ab, u32 secid);
@@ -716,6 +719,7 @@ extern int audit_enabled; 
#define audit_log_untrustedstring(a,s) do { ; } while (0)

#define audit_log_d_path(b, p, d) do { ; } while (0)

#define audit_log_key(b, k) do { ; } while (0)

#define audit_log_link_denied(o, l) do { ; } while (0)

#define audit_log_secctx(b,s) do { ; } while (0)

#define audit_enabled 0

#endif

kernel/audit.c

+21 −0
Original line number Diff line number Diff line
@@ -1449,6 +1449,27 @@ void audit_log_key(struct audit_buffer *ab, char *key) 
		audit_log_format(ab, "(null)");

}



/**

 * audit_log_link_denied - report a link restriction denial

 * @operation: specific link opreation

 * @link: the path that triggered the restriction

 */

void audit_log_link_denied(const char *operation, struct path *link)

{

	struct audit_buffer *ab;



	ab = audit_log_start(current->audit_context, GFP_KERNEL,

			     AUDIT_ANOM_LINK);

	audit_log_format(ab, "op=%s action=denied", operation);

	audit_log_format(ab, " pid=%d comm=", current->pid);

	audit_log_untrustedstring(ab, current->comm);

	audit_log_d_path(ab, " path=", link);

	audit_log_format(ab, " dev=");

	audit_log_untrustedstring(ab, link->dentry->d_inode->i_sb->s_id);

	audit_log_format(ab, " ino=%lu", link->dentry->d_inode->i_ino);

	audit_log_end(ab);

}



/**

 * audit_log_end - end one audit record

 * @ab: the audit_buffer