diff --color -ruN a/Makefile.in b/Makefile.in

--- a/Makefile.in	2022-06-23 11:31:10.168186838 +0200

+++ b/Makefile.in	2022-06-23 11:32:19.146513347 +0200

@@ -125,7 +125,7 @@

 	monitor.o monitor_wrap.o auth-krb5.o \

 	auth2-gss.o gss-serv.o gss-serv-krb5.o kexgsss.o \

 	loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \

-	sftp-server.o sftp-common.o \

+	sftp-server.o sftp-common.o sftp-realpath.o \

 	sandbox-null.o sandbox-rlimit.o sandbox-systrace.o sandbox-darwin.o \

 	sandbox-seccomp-filter.o sandbox-capsicum.o sandbox-pledge.o \

 	sandbox-solaris.o uidswap.o

@@ -217,8 +217,8 @@

 ssh-keyscan$(EXEEXT): $(LIBCOMPAT) libssh.a ssh-keyscan.o

 	$(LD) -o $@ ssh-keyscan.o $(LDFLAGS) -lssh -lopenbsd-compat -lssh $(LIBS)

-sftp-server$(EXEEXT): $(LIBCOMPAT) libssh.a sftp.o sftp-common.o sftp-server.o sftp-server-main.o

-	$(LD) -o $@ sftp-server.o sftp-common.o sftp-server-main.o $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS)

+sftp-server$(EXEEXT): $(LIBCOMPAT) libssh.a sftp.o sftp-common.o sftp-realpath.o sftp-server.o sftp-server-main.o

+	$(LD) -o $@ sftp-server.o sftp-common.o sftp-realpath.o sftp-server-main.o $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS)

 sftp$(EXEEXT): $(LIBCOMPAT) libssh.a sftp.o sftp-client.o sftp-common.o sftp-glob.o progressmeter.o

 	$(LD) -o $@ progressmeter.o sftp.o sftp-client.o sftp-common.o sftp-glob.o $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS) $(LIBEDIT)

diff --color -ruN a/sftp-realpath.c b/sftp-realpath.c

--- a/sftp-realpath.c	1970-01-01 01:00:00.000000000 +0100

+++ b/sftp-realpath.c	2022-06-23 11:35:33.193244873 +0200

@@ -0,0 +1,225 @@

+/*	$OpenBSD: sftp-realpath.c,v 1.2 2021/09/02 21:03:54 deraadt Exp $ */

+/*

+ * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>

+ *

+ * Redistribution and use in source and binary forms, with or without

+ * modification, are permitted provided that the following conditions

+ * are met:

+ * 1. Redistributions of source code must retain the above copyright

+ *    notice, this list of conditions and the following disclaimer.

+ * 2. Redistributions in binary form must reproduce the above copyright

+ *    notice, this list of conditions and the following disclaimer in the

+ *    documentation and/or other materials provided with the distribution.

+ * 3. The names of the authors may not be used to endorse or promote

+ *    products derived from this software without specific prior written

+ *    permission.

+ *

+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

+ * SUCH DAMAGE.

+ */

+

+#include "includes.h"

+

+#include <sys/types.h>

+#include <sys/stat.h>

+

+#include <errno.h>

+#include <stdlib.h>

+#include <stddef.h>

+#include <string.h>

+#include <unistd.h>

+#include <limits.h>

+

+#ifndef SYMLOOP_MAX

+# define SYMLOOP_MAX 32

+#endif

+

+/* XXX rewrite sftp-server to use POSIX realpath and remove this hack */

+

+char *sftp_realpath(const char *path, char *resolved);

+

+/*

+ * char *realpath(const char *path, char resolved[PATH_MAX]);

+ *

+ * Find the real name of path, by removing all ".", ".." and symlink

+ * components.  Returns (resolved) on success, or (NULL) on failure,

+ * in which case the path which caused trouble is left in (resolved).

+ */

+char *

+sftp_realpath(const char *path, char *resolved)

+{

+	struct stat sb;

+	char *p, *q, *s;

+	size_t left_len, resolved_len;

+	unsigned symlinks;

+	int serrno, slen, mem_allocated;

+	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];

+

+	if (path[0] == '\0') {

+		errno = ENOENT;

+		return (NULL);

+	}

+

+	serrno = errno;

+

+	if (resolved == NULL) {

+		resolved = malloc(PATH_MAX);

+		if (resolved == NULL)

+			return (NULL);

+		mem_allocated = 1;

+	} else

+		mem_allocated = 0;

+

+	symlinks = 0;

+	if (path[0] == '/') {

+		resolved[0] = '/';

+		resolved[1] = '\0';

+		if (path[1] == '\0')

+			return (resolved);

+		resolved_len = 1;

+		left_len = strlcpy(left, path + 1, sizeof(left));

+	} else {

+		if (getcwd(resolved, PATH_MAX) == NULL) {

+			if (mem_allocated)

+				free(resolved);

+			else

+				strlcpy(resolved, ".", PATH_MAX);

+			return (NULL);

+		}

+		resolved_len = strlen(resolved);

+		left_len = strlcpy(left, path, sizeof(left));

+	}

+	if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {

+		errno = ENAMETOOLONG;

+		goto err;

+	}

+

+	/*

+	 * Iterate over path components in `left'.

+	 */

+	while (left_len != 0) {

+		/*

+		 * Extract the next path component and adjust `left'

+		 * and its length.

+		 */

+		p = strchr(left, '/');

+		s = p ? p : left + left_len;

+		if (s - left >= (ptrdiff_t)sizeof(next_token)) {

+			errno = ENAMETOOLONG;

+			goto err;

+		}

+		memcpy(next_token, left, s - left);

+		next_token[s - left] = '\0';

+		left_len -= s - left;

+		if (p != NULL)

+			memmove(left, s + 1, left_len + 1);

+		if (resolved[resolved_len - 1] != '/') {

+			if (resolved_len + 1 >= PATH_MAX) {

+				errno = ENAMETOOLONG;

+				goto err;

+			}

+			resolved[resolved_len++] = '/';

+			resolved[resolved_len] = '\0';

+		}

+		if (next_token[0] == '\0')

+			continue;

+		else if (strcmp(next_token, ".") == 0)

+			continue;

+		else if (strcmp(next_token, "..") == 0) {

+			/*

+			 * Strip the last path component except when we have

+			 * single "/"

+			 */

+			if (resolved_len > 1) {

+				resolved[resolved_len - 1] = '\0';

+				q = strrchr(resolved, '/') + 1;

+				*q = '\0';

+				resolved_len = q - resolved;

+			}

+			continue;

+		}

+

+		/*

+		 * Append the next path component and lstat() it. If

+		 * lstat() fails we still can return successfully if

+		 * there are no more path components left.

+		 */

+		resolved_len = strlcat(resolved, next_token, PATH_MAX);

+		if (resolved_len >= PATH_MAX) {

+			errno = ENAMETOOLONG;

+			goto err;

+		}

+		if (lstat(resolved, &sb) != 0) {

+			if (errno == ENOENT && p == NULL) {

+				errno = serrno;

+				return (resolved);

+			}

+			goto err;

+		}

+		if (S_ISLNK(sb.st_mode)) {

+			if (symlinks++ > SYMLOOP_MAX) {

+				errno = ELOOP;

+				goto err;

+			}

+			slen = readlink(resolved, symlink, sizeof(symlink) - 1);

+			if (slen < 0)

+				goto err;

+			symlink[slen] = '\0';

+			if (symlink[0] == '/') {

+				resolved[1] = 0;

+				resolved_len = 1;

+			} else if (resolved_len > 1) {

+				/* Strip the last path component. */

+				resolved[resolved_len - 1] = '\0';

+				q = strrchr(resolved, '/') + 1;

+				*q = '\0';

+				resolved_len = q - resolved;

+			}

+

+			/*

+			 * If there are any path components left, then

+			 * append them to symlink. The result is placed

+			 * in `left'.

+			 */

+			if (p != NULL) {

+				if (symlink[slen - 1] != '/') {

+					if (slen + 1 >=

+					    (ptrdiff_t)sizeof(symlink)) {

+						errno = ENAMETOOLONG;

+						goto err;

+					}

+					symlink[slen] = '/';

+					symlink[slen + 1] = 0;

+				}

+				left_len = strlcat(symlink, left, sizeof(symlink));

+				if (left_len >= sizeof(symlink)) {

+					errno = ENAMETOOLONG;

+					goto err;

+				}

+			}

+			left_len = strlcpy(left, symlink, sizeof(left));

+		}

+	}

+

+	/*

+	 * Remove trailing slash except when the resolved pathname

+	 * is a single "/".

+	 */

+	if (resolved_len > 1 && resolved[resolved_len - 1] == '/')

+		resolved[resolved_len - 1] = '\0';

+	return (resolved);

+

+err:

+	if (mem_allocated)

+		free(resolved);

+	return (NULL);

+}

diff --color -ruN a/sftp-server.c b/sftp-server.c

--- a/sftp-server.c	2022-06-23 11:31:10.147186434 +0200

+++ b/sftp-server.c	2022-06-23 11:32:19.147513366 +0200

@@ -51,6 +51,8 @@

 #include "sftp.h"

 #include "sftp-common.h"

+char *sftp_realpath(const char *, char *); /* sftp-realpath.c */

+

 /* Our verbosity */

 static LogLevel log_level = SYSLOG_LEVEL_ERROR;

@@ -1185,7 +1187,7 @@

 	}

 	debug3("request %u: realpath", id);

 	verbose("realpath \"%s\"", path);

-	if (realpath(path, resolvedname) == NULL) {

+	if (sftp_realpath(path, resolvedname) == NULL) {

 		send_status(id, errno_to_portable(errno));

 	} else {

 		Stat s;