fix dangerous werrstr() usages

werrstr() takes a format string as its first argument.
a common error is to pass user controlled string buffers
into werrstr() that might contain format string escapes
causing werrstr() to take bogus arguments from the stack
and crash.

so instead of doing:
	werrstr(buf);

we want todo:
	werrstr("%s", buf);

or if we have a local ERRMAX sized buffer that we can override:
	errstr(buf, sizeof buf);

4 files changed, 14 insertions, 15 deletions

diff --git a/sys/src/cmd/ip/ftpd.c b/sys/src/cmd/ip/ftpd.c
index 8626ab47e..1aa395b89 100644
--- a/sys/src/cmd/ip/ftpd.c
+++ b/sys/src/cmd/ip/ftpd.c
@@ -160,14 +160,11 @@ logit(char *fmt, ...)
 {
 	char buf[8192];
 	va_list arg;
-	char errstr[ERRMAX];
 
-	rerrstr(errstr, sizeof errstr);
 	va_start(arg, fmt);
 	vseprint(buf, buf+sizeof(buf), fmt, arg);
 	va_end(arg);
 	syslog(0, FTPLOG, "%s.%s %s", nci->rsys, nci->rserv, buf);
-	werrstr(errstr, sizeof errstr);
 }
 
 static void
diff --git a/sys/src/cmd/ip/ftpfs/proto.c b/sys/src/cmd/ip/ftpfs/proto.c
index 14fe56ee9..cf4cb0f99 100644
--- a/sys/src/cmd/ip/ftpfs/proto.c
+++ b/sys/src/cmd/ip/ftpfs/proto.c
@@ -1324,7 +1324,7 @@ passive(int mode, Biobuf **bpp, char *cmda, char *cmdb)
 		close(fd);
 		if(debug)
 			fprint(2, "passive mode retrieve failed: %s\n", msg);
-		werrstr(msg);
+		werrstr("%s", msg);
 		return x;
 	}
 
diff --git a/sys/src/cmd/ip/tftpfs.c b/sys/src/cmd/ip/tftpfs.c
index 7f1fcb003..fa84d2b1d 100644
--- a/sys/src/cmd/ip/tftpfs.c
+++ b/sys/src/cmd/ip/tftpfs.c
@@ -212,7 +212,7 @@ download(void *aux)
 		msg.buf[n] = 0;
 		switch(nhgets(msg.buf)){
 		case Tftp_ERROR:
-			werrstr((char*)msg.buf+4);
+			werrstr("%s", (char*)msg.buf+4);
 			err = "%r";
 			goto out;
 
diff --git a/sys/src/cmd/ip/traceroute.c b/sys/src/cmd/ip/traceroute.c
index 33b6678b2..3113d6ded 100644
--- a/sys/src/cmd/ip/traceroute.c
+++ b/sys/src/cmd/ip/traceroute.c
@@ -140,8 +140,7 @@ static int
 udpprobe(int cfd, int dfd, char *dest, int interval)
 {
 	int n, i, rv;
-	char msg[Maxstring];
-	char err[Maxstring];
+	char msg[Maxstring], err[ERRMAX];
 
 	seek(cfd, 0, 0);
 	n = snprint(msg, sizeof msg, "connect %s", dest);
@@ -166,12 +165,13 @@ udpprobe(int cfd, int dfd, char *dest, int interval)
 			rv = 0;
 			break;
 		}
+		*err = 0;
 		errstr(err, sizeof err);
-		if(strstr(err, "alarm") == 0){
-			werrstr(err);
+		if(strcmp(err, "interrupted") != 0){
+			errstr(err, sizeof err);
 			break;
 		}
-		werrstr(err);
+		errstr(err, sizeof err);
 	}
 	alarm(0);
 	return rv;
@@ -185,7 +185,7 @@ static int
 icmpprobe(int cfd, int dfd, char *dest, int interval)
 {
 	int x, i, n, len, rv;
-	char buf[512], err[Maxstring], msg[Maxstring];
+	char buf[512], err[ERRMAX], msg[Maxstring];
 	Icmphdr *ip;
 
 	seek(cfd, 0, 0);
@@ -212,12 +212,13 @@ icmpprobe(int cfd, int dfd, char *dest, int interval)
 		n = read(dfd, buf, sizeof(buf));
 		alarm(0);
 		if(n < 0){
+			*err = 0;
 			errstr(err, sizeof err);
-			if(strstr(err, "alarm") == 0){
-				werrstr(err);
+			if(strcmp(err, "interrupted") != 0){
+				errstr(err, sizeof err);
 				break;
 			}
-			werrstr(err);
+			errstr(err, sizeof err);
 			continue;
 		}
 		x = (ip->seq[1]<<8) | ip->seq[0];
@@ -337,7 +338,7 @@ main(int argc, char **argv)
 	long *t;
 	char *net, *p;
 	char clone[Maxpath], dest[Maxstring], hop[Maxstring], dom[Maxstring];
-	char err[Maxstring];
+	char err[ERRMAX];
 	DS ds;
 
 	buckets = 0;
@@ -396,6 +397,7 @@ main(int argc, char **argv)
 				done = 1;
 				continue;
 			}
+			*err = 0;
 			errstr(err, sizeof err);
 			if(strstr(err, "refused")){
 				strcpy(hop, dest);