To prevent screwing up terminal settings when printing to the

terminal, for ASCII and UTF-8, escape bytes not forming characters
and bytes forming non-printable characters with vis(3) VIS_OCTAL.
For other character sets, abort printing of the current string in
these cases.  In particular,
* let scp(1) respect the local user's LC_CTYPE locale(1);
* sanitize data received from the remote host;
* sanitize filenames, usernames, and similar data even locally;
* take character display widths into account for the progressmeter.

This is believed to be sufficient to keep the local terminal safe
on OpenBSD, but bad things can still happen on other systems with
state-dependent locales because many places in the code print
unencoded ASCII characters into the output stream.

Using feedback from djm@ and martijn@,
various aspects discussed with many others.

deraadt@ says it should go in now, i probably already hesitated too long

7 files changed, 370 insertions, 67 deletions

diff --git a/usr.bin/ssh/lib/Makefile b/usr.bin/ssh/lib/Makefile
index e82e845b584..a5034ad6a48 100644
--- a/usr.bin/ssh/lib/Makefile
+++ b/usr.bin/ssh/lib/Makefile
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.84 2016/01/14 16:17:40 markus Exp $
+#	$OpenBSD: Makefile,v 1.85 2016/05/25 23:48:45 schwarze Exp $
 
 .PATH:		${.CURDIR}/..
 .include "${.CURDIR}/../Makefile.inc"
@@ -28,7 +28,7 @@ SRCS=	${LIB_SRCS} \
 	cleanup.c compat.c crc32.c deattack.c fatal.c \
 	hostfile.c log.c match.c nchan.c packet.c opacket.c readpass.c \
 	ttymodes.c xmalloc.c atomicio.c \
-	key.c dispatch.c kex.c mac.c uidswap.c uuencode.c misc.c \
+	key.c dispatch.c kex.c mac.c uidswap.c uuencode.c misc.c utf8.c \
 	msg.c progressmeter.c dns.c \
 	monitor_fdpass.c addrmatch.c \
 	smult_curve25519_ref.c \
diff --git a/usr.bin/ssh/progressmeter.c b/usr.bin/ssh/progressmeter.c
index 320edff4930..f66794bc19e 100644
--- a/usr.bin/ssh/progressmeter.c
+++ b/usr.bin/ssh/progressmeter.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: progressmeter.c,v 1.42 2016/03/02 22:42:40 dtucker Exp $ */
+/* $OpenBSD: progressmeter.c,v 1.43 2016/05/25 23:48:45 schwarze Exp $ */
 /*
  * Copyright (c) 2003 Nils Nordman.  All rights reserved.
  *
@@ -29,6 +29,7 @@
 
 #include <errno.h>
 #include <signal.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
@@ -37,6 +38,7 @@
 #include "progressmeter.h"
 #include "atomicio.h"
 #include "misc.h"
+#include "utf8.h"
 
 #define DEFAULT_WINSIZE 80
 #define MAX_WINSIZE 512
@@ -117,14 +119,14 @@ format_size(char *buf, int size, off_t bytes)
 void
 refresh_progress_meter(void)
 {
-	char buf[MAX_WINSIZE + 1];
+	char buf[MAX_WINSIZE * 4 + 1];
 	off_t transferred;
 	double elapsed, now;
 	int percent;
 	off_t bytes_left;
 	int cur_speed;
 	int hours, minutes, seconds;
-	int i, len;
+	size_t i;
 	int file_len;
 
 	transferred = *counter - (cur_pos ? cur_pos : start_pos);
@@ -155,17 +157,16 @@ refresh_progress_meter(void)
 		bytes_per_second = cur_speed;
 
 	/* filename */
-	buf[0] = '\0';
+	buf[0] = '\r';
+	buf[1] = '\0';
 	file_len = win_size - 35;
 	if (file_len > 0) {
-		len = snprintf(buf, file_len + 1, "\r%s", file);
-		if (len < 0)
-			len = 0;
-		if (len >= file_len + 1)
-			len = file_len;
-		for (i = len; i < file_len; i++)
-			buf[i] = ' ';
-		buf[file_len] = '\0';
+		(void) snmprintf(buf + 1, sizeof(buf) - 1 - 35,
+		    &file_len, "%s", file);
+		i = strlen(buf);
+		while (++file_len < win_size - 35 && i + 1 < sizeof(buf))
+			buf[i++] = ' ';
+		buf[i] = '\0';
 	}
 
 	/* percent of transfer done */
@@ -173,18 +174,18 @@ refresh_progress_meter(void)
 		percent = ((float)cur_pos / end_pos) * 100;
 	else
 		percent = 100;
-	snprintf(buf + strlen(buf), win_size - strlen(buf),
+	snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
 	    " %3d%% ", percent);
 
 	/* amount transferred */
-	format_size(buf + strlen(buf), win_size - strlen(buf),
+	format_size(buf + strlen(buf), sizeof(buf) - strlen(buf),
 	    cur_pos);
-	strlcat(buf, " ", win_size);
+	strlcat(buf, " ", sizeof(buf));
 
 	/* bandwidth usage */
-	format_rate(buf + strlen(buf), win_size - strlen(buf),
+	format_rate(buf + strlen(buf), sizeof(buf) - strlen(buf),
 	    (off_t)bytes_per_second);
-	strlcat(buf, "/s ", win_size);
+	strlcat(buf, "/s ", sizeof(buf));
 
 	/* ETA */
 	if (!transferred)
@@ -193,9 +194,9 @@ refresh_progress_meter(void)
 		stalled = 0;
 
 	if (stalled >= STALL_TIME)
-		strlcat(buf, "- stalled -", win_size);
+		strlcat(buf, "- stalled -", sizeof(buf));
 	else if (bytes_per_second == 0 && bytes_left)
-		strlcat(buf, "  --:-- ETA", win_size);
+		strlcat(buf, "  --:-- ETA", sizeof(buf));
 	else {
 		if (bytes_left > 0)
 			seconds = bytes_left / bytes_per_second;
@@ -208,19 +209,21 @@ refresh_progress_meter(void)
 		seconds -= minutes * 60;
 
 		if (hours != 0)
-			snprintf(buf + strlen(buf), win_size - strlen(buf),
+			snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
 			    "%d:%02d:%02d", hours, minutes, seconds);
 		else
-			snprintf(buf + strlen(buf), win_size - strlen(buf),
+			snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
 			    "  %02d:%02d", minutes, seconds);
 
 		if (bytes_left > 0)
-			strlcat(buf, " ETA", win_size);
+			strlcat(buf, " ETA", sizeof(buf));
 		else
-			strlcat(buf, "    ", win_size);
+			strlcat(buf, "    ", sizeof(buf));
 	}
+	if (win_size < 35)
+		buf[win_size] = '\0';
 
-	atomicio(vwrite, STDOUT_FILENO, buf, win_size - 1);
+	atomicio(vwrite, STDOUT_FILENO, buf, strlen(buf));
 	last_update = now;
 }
 
diff --git a/usr.bin/ssh/scp.c b/usr.bin/ssh/scp.c
index 151f1bcb6dc..c6ea4ba5c93 100644
--- a/usr.bin/ssh/scp.c
+++ b/usr.bin/ssh/scp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: scp.c,v 1.185 2016/03/02 22:43:52 dtucker Exp $ */
+/* $OpenBSD: scp.c,v 1.186 2016/05/25 23:48:45 schwarze Exp $ */
 /*
  * scp - secure remote copy.  This is basically patched BSD rcp which
  * uses ssh to do the data transfer (instead of using rcmd).
@@ -83,6 +83,7 @@
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <locale.h>
 #include <pwd.h>
 #include <signal.h>
 #include <stdarg.h>
@@ -100,6 +101,7 @@
 #include "log.h"
 #include "misc.h"
 #include "progressmeter.h"
+#include "utf8.h"
 
 #define COPY_BUFLEN	16384
 
@@ -175,7 +177,7 @@ do_local_cmd(arglist *a)
 	if (verbose_mode) {
 		fprintf(stderr, "Executing:");
 		for (i = 0; i < a->num; i++)
-			fprintf(stderr, " %s", a->list[i]);
+			fmprintf(stderr, " %s", a->list[i]);
 		fprintf(stderr, "\n");
 	}
 	if ((pid = fork()) == -1)
@@ -216,7 +218,7 @@ do_cmd(char *host, char *remuser, char *cmd, int *fdin, int *fdout)
 	int pin[2], pout[2], reserved[2];
 
 	if (verbose_mode)
-		fprintf(stderr,
+		fmprintf(stderr,
 		    "Executing: program %s host %s, user %s, command %s\n",
 		    ssh_program, host,
 		    remuser ? remuser : "(unspecified)", cmd);
@@ -291,7 +293,7 @@ do_cmd2(char *host, char *remuser, char *cmd, int fdin, int fdout)
 	int status;
 
 	if (verbose_mode)
-		fprintf(stderr,
+		fmprintf(stderr,
 		    "Executing: 2nd program %s host %s, user %s, command %s\n",
 		    ssh_program, host,
 		    remuser ? remuser : "(unspecified)", cmd);
@@ -362,6 +364,8 @@ main(int argc, char **argv)
 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 	sanitise_stdfd();
 
+	setlocale(LC_CTYPE, "");
+
 	/* Copy argv, because we modify it */
 	newargv = xcalloc(MAX(argc + 1, 1), sizeof(*newargv));
 	for (n = 0; n < argc; n++)
@@ -789,9 +793,8 @@ syserr:			run_err("%s: %s", name, strerror(errno));
 		snprintf(buf, sizeof buf, "C%04o %lld %s\n",
 		    (u_int) (stb.st_mode & FILEMODEMASK),
 		    (long long)stb.st_size, last);
-		if (verbose_mode) {
-			fprintf(stderr, "Sending file modes: %s", buf);
-		}
+		if (verbose_mode)
+			fmprintf(stderr, "Sending file modes: %s", buf);
 		(void) atomicio(vwrite, remout, buf, strlen(buf));
 		if (response() < 0)
 			goto next;
@@ -868,7 +871,7 @@ rsource(char *name, struct stat *statp)
 	(void) snprintf(path, sizeof path, "D%04o %d %.1024s\n",
 	    (u_int) (statp->st_mode & FILEMODEMASK), 0, last);
 	if (verbose_mode)
-		fprintf(stderr, "Entering directory: %s", path);
+		fmprintf(stderr, "Entering directory: %s", path);
 	(void) atomicio(vwrite, remout, path, strlen(path));
 	if (response() < 0) {
 		closedir(dirp);
@@ -908,7 +911,7 @@ sink(int argc, char **argv)
 	off_t size, statbytes;
 	unsigned long long ull;
 	int setimes, targisdir, wrerrno = 0;
-	char ch, *cp, *np, *targ, *why, *vect[1], buf[2048];
+	char ch, *cp, *np, *targ, *why, *vect[1], buf[2048], visbuf[2048];
 	struct timeval tv[2];
 
 #define	atime	tv[0]
@@ -943,12 +946,15 @@ sink(int argc, char **argv)
 		} while (cp < &buf[sizeof(buf) - 1] && ch != '\n');
 		*cp = 0;
 		if (verbose_mode)
-			fprintf(stderr, "Sink: %s", buf);
+			fmprintf(stderr, "Sink: %s", buf);
 
 		if (buf[0] == '\01' || buf[0] == '\02') {
-			if (iamremote == 0)
+			if (iamremote == 0) {
+				(void) snmprintf(visbuf, sizeof(visbuf),
+				    NULL, "%s", buf + 1);
 				(void) atomicio(vwrite, STDERR_FILENO,
-				    buf + 1, strlen(buf + 1));
+				    visbuf, strlen(visbuf));
+			}
 			if (buf[0] == '\02')
 				exit(1);
 			++errs;
@@ -1183,7 +1189,7 @@ screwup:
 int
 response(void)
 {
-	char ch, *cp, resp, rbuf[2048];
+	char ch, *cp, resp, rbuf[2048], visbuf[2048];
 
 	if (atomicio(read, remin, &resp, sizeof(resp)) != sizeof(resp))
 		lostconn(0);
@@ -1203,8 +1209,13 @@ response(void)
 			*cp++ = ch;
 		} while (cp < &rbuf[sizeof(rbuf) - 1] && ch != '\n');
 
-		if (!iamremote)
-			(void) atomicio(vwrite, STDERR_FILENO, rbuf, cp - rbuf);
+		if (!iamremote) {
+			cp[-1] = '\0';
+			(void) snmprintf(visbuf, sizeof(visbuf),
+			    NULL, "%s\n", rbuf);
+			(void) atomicio(vwrite, STDERR_FILENO,
+			    visbuf, strlen(visbuf));
+		}
 		++errs;
 		if (resp == 1)
 			return (-1);
@@ -1242,7 +1253,7 @@ run_err(const char *fmt,...)
 
 	if (!iamremote) {
 		va_start(ap, fmt);
-		vfprintf(stderr, fmt, ap);
+		vfmprintf(stderr, fmt, ap);
 		va_end(ap);
 		fprintf(stderr, "\n");
 	}
@@ -1288,7 +1299,7 @@ okname(char *cp0)
 	} while (*++cp);
 	return (1);
 
-bad:	fprintf(stderr, "%s: invalid user name\n", cp0);
+bad:	fmprintf(stderr, "%s: invalid user name\n", cp0);
 	return (0);
 }
 
diff --git a/usr.bin/ssh/sftp-client.c b/usr.bin/ssh/sftp-client.c
index 7baf7726b7a..17c5585421d 100644
--- a/usr.bin/ssh/sftp-client.c
+++ b/usr.bin/ssh/sftp-client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-client.c,v 1.123 2016/05/02 08:49:03 djm Exp $ */
+/* $OpenBSD: sftp-client.c,v 1.124 2016/05/25 23:48:45 schwarze Exp $ */
 /*
  * Copyright (c) 2001-2004 Damien Miller <djm@openbsd.org>
  *
@@ -46,6 +46,7 @@
 #include "atomicio.h"
 #include "progressmeter.h"
 #include "misc.h"
+#include "utf8.h"
 
 #include "sftp.h"
 #include "sftp-common.h"
@@ -603,7 +604,7 @@ do_lsreaddir(struct sftp_conn *conn, const char *path, int print_flag,
 			}
 
 			if (print_flag)
-				printf("%s\n", longname);
+				mprintf("%s\n", longname);
 
 			/*
 			 * Directory entries should never contain '/'
@@ -1449,7 +1450,7 @@ download_dir_internal(struct sftp_conn *conn, const char *src, const char *dst,
 		return -1;
 	}
 	if (print_flag)
-		printf("Retrieving %s\n", src);
+		mprintf("Retrieving %s\n", src);
 
 	if (dirattrib->flags & SSH2_FILEXFER_ATTR_PERMISSIONS)
 		mode = dirattrib->perm & 01777;
@@ -1781,7 +1782,7 @@ upload_dir_internal(struct sftp_conn *conn, const char *src, const char *dst,
 		return -1;
 	}
 	if (print_flag)
-		printf("Entering %s\n", src);
+		mprintf("Entering %s\n", src);
 
 	attrib_clear(&a);
 	stat_to_attrib(&sb, &a);
diff --git a/usr.bin/ssh/sftp.c b/usr.bin/ssh/sftp.c
index 706e5486312..daeb6784d10 100644
--- a/usr.bin/ssh/sftp.c
+++ b/usr.bin/ssh/sftp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp.c,v 1.173 2016/04/08 08:19:17 djm Exp $ */
+/* $OpenBSD: sftp.c,v 1.174 2016/05/25 23:48:45 schwarze Exp $ */
 /*
  * Copyright (c) 2001-2004 Damien Miller <djm@openbsd.org>
  *
@@ -31,6 +31,7 @@
 #include <libgen.h>
 #include <locale.h>
 #include <signal.h>
+#include <stdarg.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -43,6 +44,7 @@
 #include "log.h"
 #include "pathnames.h"
 #include "misc.h"
+#include "utf8.h"
 
 #include "sftp.h"
 #include "ssherr.h"
@@ -622,9 +624,11 @@ process_get(struct sftp_conn *conn, char *src, char *dst, char *pwd,
 
 		resume |= global_aflag;
 		if (!quiet && resume)
-			printf("Resuming %s to %s\n", g.gl_pathv[i], abs_dst);
+			mprintf("Resuming %s to %s\n",
+			    g.gl_pathv[i], abs_dst);
 		else if (!quiet && !resume)
-			printf("Fetching %s to %s\n", g.gl_pathv[i], abs_dst);
+			mprintf("Fetching %s to %s\n",
+			    g.gl_pathv[i], abs_dst);
 		if (pathname_is_dir(g.gl_pathv[i]) && (rflag || global_rflag)) {
 			if (download_dir(conn, g.gl_pathv[i], abs_dst, NULL,
 			    pflag || global_pflag, 1, resume,
@@ -713,10 +717,11 @@ process_put(struct sftp_conn *conn, char *src, char *dst, char *pwd,
 
                 resume |= global_aflag;
 		if (!quiet && resume)
-			printf("Resuming upload of %s to %s\n", g.gl_pathv[i],
-				abs_dst);
+			mprintf("Resuming upload of %s to %s\n",
+			    g.gl_pathv[i], abs_dst);
 		else if (!quiet && !resume)
-			printf("Uploading %s to %s\n", g.gl_pathv[i], abs_dst);
+			mprintf("Uploading %s to %s\n",
+			    g.gl_pathv[i], abs_dst);
 		if (pathname_is_dir(g.gl_pathv[i]) && (rflag || global_rflag)) {
 			if (upload_dir(conn, g.gl_pathv[i], abs_dst,
 			    pflag || global_pflag, 1, resume,
@@ -817,12 +822,12 @@ do_ls_dir(struct sftp_conn *conn, char *path, char *strip_path, int lflag)
 				attrib_to_stat(&d[n]->a, &sb);
 				lname = ls_file(fname, &sb, 1,
 				    (lflag & LS_SI_UNITS));
-				printf("%s\n", lname);
+				mprintf("%s\n", lname);
 				free(lname);
 			} else
-				printf("%s\n", d[n]->longname);
+				mprintf("%s\n", d[n]->longname);
 		} else {
-			printf("%-*s", colspace, fname);
+			mprintf("%-*s", colspace, fname);
 			if (c >= columns) {
 				printf("\n");
 				c = 1;
@@ -903,10 +908,10 @@ do_globbed_ls(struct sftp_conn *conn, char *path, char *strip_path,
 			}
 			lname = ls_file(fname, g.gl_statv[i], 1,
 			    (lflag & LS_SI_UNITS));
-			printf("%s\n", lname);
+			mprintf("%s\n", lname);
 			free(lname);
 		} else {
-			printf("%-*s", colspace, fname);
+			mprintf("%-*s", colspace, fname);
 			if (c >= columns) {
 				printf("\n");
 				c = 1;
@@ -1434,7 +1439,7 @@ parse_dispatch_command(struct sftp_conn *conn, const char *cmd, char **pwd,
 		remote_glob(conn, path1, GLOB_NOCHECK, NULL, &g);
 		for (i = 0; g.gl_pathv[i] && !interrupted; i++) {
 			if (!quiet)
-				printf("Removing %s\n", g.gl_pathv[i]);
+				mprintf("Removing %s\n", g.gl_pathv[i]);
 			err = do_rm(conn, g.gl_pathv[i]);
 			if (err != 0 && err_abort)
 				break;
@@ -1534,7 +1539,8 @@ parse_dispatch_command(struct sftp_conn *conn, const char *cmd, char **pwd,
 		remote_glob(conn, path1, GLOB_NOCHECK, NULL, &g);
 		for (i = 0; g.gl_pathv[i] && !interrupted; i++) {
 			if (!quiet)
-				printf("Changing mode on %s\n", g.gl_pathv[i]);
+				mprintf("Changing mode on %s\n",
+				    g.gl_pathv[i]);
 			err = do_setstat(conn, g.gl_pathv[i], &a);
 			if (err != 0 && err_abort)
 				break;
@@ -1564,12 +1570,12 @@ parse_dispatch_command(struct sftp_conn *conn, const char *cmd, char **pwd,
 			aa->flags &= SSH2_FILEXFER_ATTR_UIDGID;
 			if (cmdnum == I_CHOWN) {
 				if (!quiet)
-					printf("Changing owner on %s\n",
+					mprintf("Changing owner on %s\n",
 					    g.gl_pathv[i]);
 				aa->uid = n_arg;
 			} else {
 				if (!quiet)
-					printf("Changing group on %s\n",
+					mprintf("Changing group on %s\n",
 					    g.gl_pathv[i]);
 				aa->gid = n_arg;
 			}
@@ -1579,7 +1585,7 @@ parse_dispatch_command(struct sftp_conn *conn, const char *cmd, char **pwd,
 		}
 		break;
 	case I_PWD:
-		printf("Remote working directory: %s\n", *pwd);
+		mprintf("Remote working directory: %s\n", *pwd);
 		break;
 	case I_LPWD:
 		if (!getcwd(path_buf, sizeof(path_buf))) {
@@ -1587,7 +1593,7 @@ parse_dispatch_command(struct sftp_conn *conn, const char *cmd, char **pwd,
 			err = -1;
 			break;
 		}
-		printf("Local working directory: %s\n", path_buf);
+		mprintf("Local working directory: %s\n", path_buf);
 		break;
 	case I_QUIT:
 		/* Processed below */
@@ -1655,7 +1661,7 @@ complete_display(char **list, u_int len)
 	for (y = 0; list[y]; y++) {
 		llen = strlen(list[y]);
 		tmp = llen > len ? list[y] + len : "";
-		printf("%-*s", colspace, tmp);
+		mprintf("%-*s", colspace, tmp);
 		if (m >= columns) {
 			printf("\n");
 			m = 1;
@@ -2036,7 +2042,7 @@ interactive_loop(struct sftp_conn *conn, char *file1, char *file2)
 
 		if (remote_is_dir(conn, dir) && file2 == NULL) {
 			if (!quiet)
-				printf("Changing to: %s\n", dir);
+				mprintf("Changing to: %s\n", dir);
 			snprintf(cmd, sizeof cmd, "cd \"%s\"", dir);
 			if (parse_dispatch_command(conn, cmd,
 			    &remote_path, 1) != 0) {
@@ -2082,7 +2088,7 @@ interactive_loop(struct sftp_conn *conn, char *file1, char *file2)
 				break;
 			}
 			if (!interactive) { /* Echo command */
-				printf("sftp> %s", cmd);
+				mprintf("sftp> %s", cmd);
 				if (strlen(cmd) > 0 &&
 				    cmd[strlen(cmd) - 1] != '\n')
 					printf("\n");
diff --git a/usr.bin/ssh/utf8.c b/usr.bin/ssh/utf8.c
new file mode 100644
index 00000000000..d6089bdecf5
--- /dev/null
+++ b/usr.bin/ssh/utf8.c
@@ -0,0 +1,258 @@
+/* $OpenBSD: utf8.c,v 1.1 2016/05/25 23:48:45 schwarze Exp $ */
+/*
+ * Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Utility functions for multibyte-character handling,
+ * in particular to sanitize untrusted strings for terminal output.
+ */
+
+#include <sys/types.h>
+#include <langinfo.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <vis.h>
+#include <wchar.h>
+
+#include "utf8.h"
+
+static int	 dangerous_locale(void);
+static int	 vasnmprintf(char **, size_t, int *, const char *, va_list);
+
+
+/*
+ * For US-ASCII and UTF-8 encodings, we can safely recover from
+ * encoding errors and from non-printable characters.  For any
+ * other encodings, err to the side of caution and abort parsing:
+ * For state-dependent encodings, recovery is impossible.
+ * For arbitrary encodings, replacement of non-printable
+ * characters would be non-trivial and too fragile.
+ */
+
+static int
+dangerous_locale(void) {
+	char	*loc;
+
+	loc = nl_langinfo(CODESET);
+	return strcmp(loc, "US-ASCII") && strcmp(loc, "UTF-8");
+}
+
+/*
+ * The following two functions limit the number of bytes written,
+ * including the terminating '\0', to sz.  Unless wp is NULL,
+ * they limit the number of display columns occupied to *wp.
+ * Whichever is reached first terminates the output string.
+ * To stay close to the standard interfaces, they return the number of
+ * non-NUL bytes that would have been written if both were unlimited.
+ * If wp is NULL, newline, carriage return, and tab are allowed;
+ * otherwise, the actual number of columns occupied by what was
+ * written is returned in *wp.
+ */
+
+static int
+vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
+{
+	char	*src;	/* Source string returned from vasprintf. */
+	char	*sp;	/* Pointer into src. */
+	char	*dst;	/* Destination string to be returned. */
+	char	*dp;	/* Pointer into dst. */
+	char	*tp;	/* Temporary pointer for dst. */
+	size_t	 sz;	/* Number of bytes allocated for dst. */
+	size_t	 tsz;	/* Temporary size while extending dst. */
+	wchar_t	 wc;	/* Wide character at sp. */
+	int	 len;	/* Number of bytes in the character at sp. */
+	int	 ret;	/* Number of bytes needed to format src. */
+	int	 width;	/* Display width of the character wc. */
+	int	 total_width, max_width, print;
+
+	src = dst = NULL;
+	if (vasprintf(&src, fmt, ap) <= 0)
+		goto fail;
+
+	sz = strlen(src);
+	if ((dst = malloc(sz)) == NULL)
+		goto fail;
+
+	if (maxsz > INT_MAX)
+		maxsz = INT_MAX;
+
+	sp = src;
+	dp = dst;
+	ret = 0;
+	print = 1;
+	total_width = 0;
+	max_width = wp == NULL ? INT_MAX : *wp;
+	while (*sp != '\0') {
+		if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
+			(void)mbtowc(NULL, NULL, MB_CUR_MAX);
+			if (dangerous_locale()) {
+				ret = -1;
+				break;
+			}
+			len = 1;
+			width = -1;
+		} else if (wp == NULL &&
+		    (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
+			/*
+			 * Don't use width uninitialized; the actual
+			 * value doesn't matter because total_width
+			 * is only returned for wp != NULL.
+			 */
+			width = 0;
+		} else if ((width = wcwidth(wc)) == -1 &&
+		    dangerous_locale()) {
+			ret = -1;
+			break;
+		}
+
+		/* Valid, printable character. */
+
+		if (width >= 0) {
+			if (print && (dp - dst >= (int)maxsz - len ||
+			    total_width > max_width - width))
+				print = 0;
+			if (print) {
+				total_width += width;
+				memcpy(dp, sp, len);
+				dp += len;
+			}
+			sp += len;
+			if (ret >= 0)
+				ret += len;
+			continue;
+		}
+
+		/* Escaping required. */
+
+		while (len > 0) {
+			if (print && (dp - dst >= (int)maxsz - 4 ||
+			    total_width > max_width - 4))
+				print = 0;
+			if (print) {
+				if (dp + 4 >= dst + sz) {
+					tsz = sz + 128;
+					if (tsz > maxsz)
+						tsz = maxsz;
+					tp = realloc(dst, tsz);
+					if (tp == NULL) {
+						ret = -1;
+						break;
+					}
+					dp = tp + (dp - dst);
+					dst = tp;
+					sz = tsz;
+				}
+				tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
+				width = tp - dp;
+				total_width += width;
+				dp = tp;
+			} else
+				width = 4;
+			len--;
+			sp++;
+			if (ret >= 0)
+				ret += width;
+		}
+		if (len > 0)
+			break;
+	}
+	free(src);
+	*dp = '\0';
+	*str = dst;
+	if (wp != NULL)
+		*wp = total_width;
+
+	/*
+	 * If the string was truncated by the width limit but
+	 * would have fit into the size limit, the only sane way
+	 * to report the problem is using the return value, such
+	 * that the usual idiom "if (ret < 0 || ret >= sz) error"
+	 * works as expected.
+	 */
+
+	if (ret < (int)maxsz && !print)
+		ret = -1;
+	return ret;
+
+fail:
+	free(src);
+	free(dst);
+	*str = NULL;
+	if (wp != NULL)
+		*wp = 0;
+	return -1;
+}
+
+int
+snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
+{
+	va_list	 ap;
+	char	*cp;
+	int	 ret;
+
+	va_start(ap, fmt);
+	ret = vasnmprintf(&cp, sz, wp, fmt, ap);
+	va_end(ap);
+	(void)strlcpy(str, cp, sz);
+	free(cp);
+	return ret;
+}
+
+/*
+ * To stay close to the standard interfaces, the following functions
+ * return the number of non-NUL bytes written.
+ */
+
+int
+vfmprintf(FILE *stream, const char *fmt, va_list ap)
+{
+	char	*str;
+	int	 ret;
+
+	if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0)
+		return -1;
+	if (fputs(str, stream) == EOF)
+		ret = -1;
+	free(str);
+	return ret;
+}
+
+int
+fmprintf(FILE *stream, const char *fmt, ...)
+{
+	va_list	 ap;
+	int	 ret;
+
+	va_start(ap, fmt);
+	ret = vfmprintf(stream, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+
+int
+mprintf(const char *fmt, ...)
+{
+	va_list	 ap;
+	int	 ret;
+
+	va_start(ap, fmt);
+	ret = vfmprintf(stdout, fmt, ap);
+	va_end(ap);
+	return ret;
+}
diff --git a/usr.bin/ssh/utf8.h b/usr.bin/ssh/utf8.h
new file mode 100644
index 00000000000..43ce1d55d9a
--- /dev/null
+++ b/usr.bin/ssh/utf8.h
@@ -0,0 +1,24 @@
+/* $OpenBSD: utf8.h,v 1.1 2016/05/25 23:48:45 schwarze Exp $ */
+/*
+ * Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+int	 mprintf(const char *, ...)
+	     __attribute__((format(printf, 1, 2)));
+int	 fmprintf(FILE *, const char *, ...)
+	     __attribute__((format(printf, 2, 3)));
+int	 vfmprintf(FILE *, const char *, va_list);
+int	 snmprintf(char *, size_t, int *, const char *, ...)
+	     __attribute__((format(printf, 4, 5)));