Commit b50eba7e authored Sep 16, 2013 by Richard Guy Briggs Committed by Eric Paris Nov 05, 2013

audit: format user messages to size of MAX_AUDIT_MESSAGE_LENGTH

Messages of type AUDIT_USER_TTY were being formatted to 1024 octets,
truncating messages approaching MAX_AUDIT_MESSAGE_LENGTH (8970 octets).

Set the formatting to 8560 characters, given maximum estimates for prefix and
suffix budgets.

See the problem discussion:
https://www.redhat.com/archives/linux-audit/2009-January/msg00030.html

And the new size rationale:
https://www.redhat.com/archives/linux-audit/2013-September/msg00016.html



Test ~8k messages with:
auditctl -m "$(for i in $(seq -w 001 820);do echo -n "${i}0______";done)"

Reported-by: LC Bruzenak <lenny@magitekltd.com>
Reported-by: Justin Stephenson <jstephen@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

parent 6e466452

include/uapi/linux/audit.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -358,6 +358,12 @@ enum {
		#define AUDIT_PERM_READ 4
		#define AUDIT_PERM_ATTR 8

		/* MAX_AUDIT_MESSAGE_LENGTH is set in audit:lib/libaudit.h as:
		* 8970 // PATH_MAX2+CONTEXT_SIZE2+11+256+1
		* max header+body+tailer: 44 + 29 + 32 + 262 + 7 + pad
		*/
		#define AUDIT_MESSAGE_TEXT_MAX 8560

		struct audit_status {
		__u32 mask; /* Bit mask for valid entries */
		__u32 enabled; /* 1 = enabled, 0 = disabled */

kernel/audit.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -715,7 +715,8 @@ static int audit_receive_msg(struct sk_buff skb, struct nlmsghdr nlh)
		}
		audit_log_common_recv_msg(&ab, msg_type);
		if (msg_type != AUDIT_USER_TTY)
		audit_log_format(ab, " msg='%.1024s'",
		audit_log_format(ab, " msg='%.*s'",
		AUDIT_MESSAGE_TEXT_MAX,
		(char *)data);
		else {
		int size;

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