From c153b3612b7c9f24a0f5af43618a646545ed6e22 Mon Sep 17 00:00:00 2001
From: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
Date: Mon, 30 Sep 2019 12:42:13 +0100
Subject: [PATCH] Improve address logging on early exit messages

Change 'Early exit' and 'Exit before auth' messages to include the IP
address & port as part of the message.

This allows log scanning utilities such as 'fail2ban' to obtain the
offending IP address as part of the failure event instead of extracting
the PID from the message and then scanning the log again for match
'child connection from' messages

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
---
 svr-auth.c    | 18 +++++++-----------
 svr-session.c | 20 ++++++++++++++------
 2 files changed, 21 insertions(+), 17 deletions(-)

--- a/svr-auth.c
+++ b/svr-auth.c
@@ -241,8 +241,7 @@ static int checkusername(const char *use
 	}
 
 	if (strlen(username) != userlen) {
-		dropbear_exit("Attempted username with a null byte from %s",
-			svr_ses.addrstring);
+		dropbear_exit("Attempted username with a null byte");
 	}
 
 	if (ses.authstate.username == NULL) {
@@ -252,8 +251,7 @@ static int checkusername(const char *use
 	} else {
 		/* check username hasn't changed */
 		if (strcmp(username, ses.authstate.username) != 0) {
-			dropbear_exit("Client trying multiple usernames from %s",
-				svr_ses.addrstring);
+			dropbear_exit("Client trying multiple usernames");
 		}
 	}
 
@@ -268,8 +266,7 @@ static int checkusername(const char *use
 	if (!ses.authstate.pw_name) {
 		TRACE(("leave checkusername: user '%s' doesn't exist", username))
 		dropbear_log(LOG_WARNING,
-				"Login attempt for nonexistent user from %s",
-				svr_ses.addrstring);
+				"Login attempt for nonexistent user");
 		ses.authstate.checkusername_failed = 1;
 		return DROPBEAR_FAILURE;
 	}
@@ -279,9 +276,8 @@ static int checkusername(const char *use
 	if (!(DROPBEAR_SVR_MULTIUSER && uid == 0) && uid != ses.authstate.pw_uid) {
 		TRACE(("running as nonroot, only server uid is allowed"))
 		dropbear_log(LOG_WARNING,
-				"Login attempt with wrong user %s from %s",
-				ses.authstate.pw_name,
-				svr_ses.addrstring);
+				"Login attempt with wrong user %s",
+				ses.authstate.pw_name);
 		ses.authstate.checkusername_failed = 1;
 		return DROPBEAR_FAILURE;
 	}
@@ -440,8 +436,8 @@ void send_msg_userauth_failure(int parti
 		} else {
 			userstr = ses.authstate.pw_name;
 		}
-		dropbear_exit("Max auth tries reached - user '%s' from %s",
-				userstr, svr_ses.addrstring);
+		dropbear_exit("Max auth tries reached - user '%s'",
+				userstr);
 	}
 	
 	TRACE(("leave send_msg_userauth_failure"))
--- a/svr-session.c
+++ b/svr-session.c
@@ -149,28 +149,36 @@ void svr_session(int sock, int childpipe
 void svr_dropbear_exit(int exitcode, const char* format, va_list param) {
 	char exitmsg[150];
 	char fullmsg[300];
+	char fromaddr[60];
 	int i;
 
 	/* Render the formatted exit message */
 	vsnprintf(exitmsg, sizeof(exitmsg), format, param);
 
+	/* svr_ses.addrstring may not be set for some early exits, or for
+	the listener process */
+	fromaddr[0] = '\0';
+	if (svr_ses.addrstring) {
+	    snprintf(fromaddr, sizeof(fromaddr), " from <%s>", svr_ses.addrstring);
+    }
+
 	/* Add the prefix depending on session/auth state */
 	if (!ses.init_done) {
 		/* before session init */
-		snprintf(fullmsg, sizeof(fullmsg), "Early exit: %s", exitmsg);
+		snprintf(fullmsg, sizeof(fullmsg), "Early exit%s: %s", fromaddr, exitmsg);
 	} else if (ses.authstate.authdone) {
 		/* user has authenticated */
 		snprintf(fullmsg, sizeof(fullmsg),
-				"Exit (%s): %s", 
-				ses.authstate.pw_name, exitmsg);
+				"Exit (%s)%s: %s", 
+				ses.authstate.pw_name, fromaddr, exitmsg);
 	} else if (ses.authstate.pw_name) {
 		/* we have a potential user */
 		snprintf(fullmsg, sizeof(fullmsg), 
-				"Exit before auth (user '%s', %u fails): %s",
-				ses.authstate.pw_name, ses.authstate.failcount, exitmsg);
+				"Exit before auth%s: (user '%s', %u fails): %s",
+				fromaddr, ses.authstate.pw_name, ses.authstate.failcount, exitmsg);
 	} else {
 		/* before userauth */
-		snprintf(fullmsg, sizeof(fullmsg), "Exit before auth: %s", exitmsg);
+		snprintf(fullmsg, sizeof(fullmsg), "Exit before auth%s: %s", fromaddr, exitmsg);
 	}
 
 	dropbear_log(LOG_INFO, "%s", fullmsg);