Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2108 insertions, 0 deletions

diff --git a/sftp-server.c b/sftp-server.c
new file mode 100644
index 0000000..fe61a35
--- /dev/null
+++ b/sftp-server.c
@@ -0,0 +1,2108 @@
+/* $OpenBSD: sftp-server.c,v 1.145 2022/11/09 09:04:12 dtucker Exp $ */
+/*
+ * Copyright (c) 2000-2004 Markus Friedl.  All rights reserved.
+ *
+ * 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.
+ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/resource.h>
+#ifdef HAVE_SYS_TIME_H
+# include <sys/time.h>
+#endif
+#ifdef HAVE_SYS_MOUNT_H
+#include <sys/mount.h>
+#endif
+#ifdef HAVE_SYS_STATVFS_H
+#include <sys/statvfs.h>
+#endif
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+#include <pwd.h>
+#include <grp.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <stdarg.h>
+
+#include "atomicio.h"
+#include "xmalloc.h"
+#include "sshbuf.h"
+#include "ssherr.h"
+#include "log.h"
+#include "misc.h"
+#include "match.h"
+#include "uidswap.h"
+
+#include "sftp.h"
+#include "sftp-common.h"
+
+char *sftp_realpath(const char *, char *); /* sftp-realpath.c */
+
+/* Maximum data read that we are willing to accept */
+#define SFTP_MAX_READ_LENGTH (SFTP_MAX_MSG_LENGTH - 1024)
+
+/* Our verbosity */
+static LogLevel log_level = SYSLOG_LEVEL_ERROR;
+
+/* Our client */
+static struct passwd *pw = NULL;
+static char *client_addr = NULL;
+
+/* input and output queue */
+struct sshbuf *iqueue;
+struct sshbuf *oqueue;
+
+/* Version of client */
+static u_int version;
+
+/* SSH2_FXP_INIT received */
+static int init_done;
+
+/* Disable writes */
+static int readonly;
+
+/* Requests that are allowed/denied */
+static char *request_allowlist, *request_denylist;
+
+/* portable attributes, etc. */
+typedef struct Stat Stat;
+
+struct Stat {
+	char *name;
+	char *long_name;
+	Attrib attrib;
+};
+
+/* Packet handlers */
+static void process_open(u_int32_t id);
+static void process_close(u_int32_t id);
+static void process_read(u_int32_t id);
+static void process_write(u_int32_t id);
+static void process_stat(u_int32_t id);
+static void process_lstat(u_int32_t id);
+static void process_fstat(u_int32_t id);
+static void process_setstat(u_int32_t id);
+static void process_fsetstat(u_int32_t id);
+static void process_opendir(u_int32_t id);
+static void process_readdir(u_int32_t id);
+static void process_remove(u_int32_t id);
+static void process_mkdir(u_int32_t id);
+static void process_rmdir(u_int32_t id);
+static void process_realpath(u_int32_t id);
+static void process_rename(u_int32_t id);
+static void process_readlink(u_int32_t id);
+static void process_symlink(u_int32_t id);
+static void process_extended_posix_rename(u_int32_t id);
+static void process_extended_statvfs(u_int32_t id);
+static void process_extended_fstatvfs(u_int32_t id);
+static void process_extended_hardlink(u_int32_t id);
+static void process_extended_fsync(u_int32_t id);
+static void process_extended_lsetstat(u_int32_t id);
+static void process_extended_limits(u_int32_t id);
+static void process_extended_expand(u_int32_t id);
+static void process_extended_copy_data(u_int32_t id);
+static void process_extended_home_directory(u_int32_t id);
+static void process_extended_get_users_groups_by_id(u_int32_t id);
+static void process_extended(u_int32_t id);
+
+struct sftp_handler {
+	const char *name;	/* user-visible name for fine-grained perms */
+	const char *ext_name;	/* extended request name */
+	u_int type;		/* packet type, for non extended packets */
+	void (*handler)(u_int32_t);
+	int does_write;		/* if nonzero, banned for readonly mode */
+};
+
+static const struct sftp_handler handlers[] = {
+	/* NB. SSH2_FXP_OPEN does the readonly check in the handler itself */
+	{ "open", NULL, SSH2_FXP_OPEN, process_open, 0 },
+	{ "close", NULL, SSH2_FXP_CLOSE, process_close, 0 },
+	{ "read", NULL, SSH2_FXP_READ, process_read, 0 },
+	{ "write", NULL, SSH2_FXP_WRITE, process_write, 1 },
+	{ "lstat", NULL, SSH2_FXP_LSTAT, process_lstat, 0 },
+	{ "fstat", NULL, SSH2_FXP_FSTAT, process_fstat, 0 },
+	{ "setstat", NULL, SSH2_FXP_SETSTAT, process_setstat, 1 },
+	{ "fsetstat", NULL, SSH2_FXP_FSETSTAT, process_fsetstat, 1 },
+	{ "opendir", NULL, SSH2_FXP_OPENDIR, process_opendir, 0 },
+	{ "readdir", NULL, SSH2_FXP_READDIR, process_readdir, 0 },
+	{ "remove", NULL, SSH2_FXP_REMOVE, process_remove, 1 },
+	{ "mkdir", NULL, SSH2_FXP_MKDIR, process_mkdir, 1 },
+	{ "rmdir", NULL, SSH2_FXP_RMDIR, process_rmdir, 1 },
+	{ "realpath", NULL, SSH2_FXP_REALPATH, process_realpath, 0 },
+	{ "stat", NULL, SSH2_FXP_STAT, process_stat, 0 },
+	{ "rename", NULL, SSH2_FXP_RENAME, process_rename, 1 },
+	{ "readlink", NULL, SSH2_FXP_READLINK, process_readlink, 0 },
+	{ "symlink", NULL, SSH2_FXP_SYMLINK, process_symlink, 1 },
+	{ NULL, NULL, 0, NULL, 0 }
+};
+
+/* SSH2_FXP_EXTENDED submessages */
+static const struct sftp_handler extended_handlers[] = {
+	{ "posix-rename", "posix-rename@openssh.com", 0,
+	    process_extended_posix_rename, 1 },
+	{ "statvfs", "statvfs@openssh.com", 0, process_extended_statvfs, 0 },
+	{ "fstatvfs", "fstatvfs@openssh.com", 0, process_extended_fstatvfs, 0 },
+	{ "hardlink", "hardlink@openssh.com", 0, process_extended_hardlink, 1 },
+	{ "fsync", "fsync@openssh.com", 0, process_extended_fsync, 1 },
+	{ "lsetstat", "lsetstat@openssh.com", 0, process_extended_lsetstat, 1 },
+	{ "limits", "limits@openssh.com", 0, process_extended_limits, 0 },
+	{ "expand-path", "expand-path@openssh.com", 0,
+	    process_extended_expand, 0 },
+	{ "copy-data", "copy-data", 0, process_extended_copy_data, 1 },
+	{ "home-directory", "home-directory", 0,
+	    process_extended_home_directory, 0 },
+	{ "users-groups-by-id", "users-groups-by-id@openssh.com", 0,
+	    process_extended_get_users_groups_by_id, 0 },
+	{ NULL, NULL, 0, NULL, 0 }
+};
+
+static const struct sftp_handler *
+extended_handler_byname(const char *name)
+{
+	int i;
+
+	for (i = 0; extended_handlers[i].handler != NULL; i++) {
+		if (strcmp(name, extended_handlers[i].ext_name) == 0)
+			return &extended_handlers[i];
+	}
+	return NULL;
+}
+
+static int
+request_permitted(const struct sftp_handler *h)
+{
+	char *result;
+
+	if (readonly && h->does_write) {
+		verbose("Refusing %s request in read-only mode", h->name);
+		return 0;
+	}
+	if (request_denylist != NULL &&
+	    ((result = match_list(h->name, request_denylist, NULL))) != NULL) {
+		free(result);
+		verbose("Refusing denylisted %s request", h->name);
+		return 0;
+	}
+	if (request_allowlist != NULL &&
+	    ((result = match_list(h->name, request_allowlist, NULL))) != NULL) {
+		free(result);
+		debug2("Permitting allowlisted %s request", h->name);
+		return 1;
+	}
+	if (request_allowlist != NULL) {
+		verbose("Refusing non-allowlisted %s request", h->name);
+		return 0;
+	}
+	return 1;
+}
+
+static int
+errno_to_portable(int unixerrno)
+{
+	int ret = 0;
+
+	switch (unixerrno) {
+	case 0:
+		ret = SSH2_FX_OK;
+		break;
+	case ENOENT:
+	case ENOTDIR:
+	case EBADF:
+	case ELOOP:
+		ret = SSH2_FX_NO_SUCH_FILE;
+		break;
+	case EPERM:
+	case EACCES:
+	case EFAULT:
+		ret = SSH2_FX_PERMISSION_DENIED;
+		break;
+	case ENAMETOOLONG:
+	case EINVAL:
+		ret = SSH2_FX_BAD_MESSAGE;
+		break;
+	case ENOSYS:
+		ret = SSH2_FX_OP_UNSUPPORTED;
+		break;
+	default:
+		ret = SSH2_FX_FAILURE;
+		break;
+	}
+	return ret;
+}
+
+static int
+flags_from_portable(int pflags)
+{
+	int flags = 0;
+
+	if ((pflags & SSH2_FXF_READ) &&
+	    (pflags & SSH2_FXF_WRITE)) {
+		flags = O_RDWR;
+	} else if (pflags & SSH2_FXF_READ) {
+		flags = O_RDONLY;
+	} else if (pflags & SSH2_FXF_WRITE) {
+		flags = O_WRONLY;
+	}
+	if (pflags & SSH2_FXF_APPEND)
+		flags |= O_APPEND;
+	if (pflags & SSH2_FXF_CREAT)
+		flags |= O_CREAT;
+	if (pflags & SSH2_FXF_TRUNC)
+		flags |= O_TRUNC;
+	if (pflags & SSH2_FXF_EXCL)
+		flags |= O_EXCL;
+	return flags;
+}
+
+static const char *
+string_from_portable(int pflags)
+{
+	static char ret[128];
+
+	*ret = '\0';
+
+#define PAPPEND(str)	{				\
+		if (*ret != '\0')			\
+			strlcat(ret, ",", sizeof(ret));	\
+		strlcat(ret, str, sizeof(ret));		\
+	}
+
+	if (pflags & SSH2_FXF_READ)
+		PAPPEND("READ")
+	if (pflags & SSH2_FXF_WRITE)
+		PAPPEND("WRITE")
+	if (pflags & SSH2_FXF_APPEND)
+		PAPPEND("APPEND")
+	if (pflags & SSH2_FXF_CREAT)
+		PAPPEND("CREATE")
+	if (pflags & SSH2_FXF_TRUNC)
+		PAPPEND("TRUNCATE")
+	if (pflags & SSH2_FXF_EXCL)
+		PAPPEND("EXCL")
+
+	return ret;
+}
+
+/* handle handles */
+
+typedef struct Handle Handle;
+struct Handle {
+	int use;
+	DIR *dirp;
+	int fd;
+	int flags;
+	char *name;
+	u_int64_t bytes_read, bytes_write;
+	int next_unused;
+};
+
+enum {
+	HANDLE_UNUSED,
+	HANDLE_DIR,
+	HANDLE_FILE
+};
+
+static Handle *handles = NULL;
+static u_int num_handles = 0;
+static int first_unused_handle = -1;
+
+static void handle_unused(int i)
+{
+	handles[i].use = HANDLE_UNUSED;
+	handles[i].next_unused = first_unused_handle;
+	first_unused_handle = i;
+}
+
+static int
+handle_new(int use, const char *name, int fd, int flags, DIR *dirp)
+{
+	int i;
+
+	if (first_unused_handle == -1) {
+		if (num_handles + 1 <= num_handles)
+			return -1;
+		num_handles++;
+		handles = xreallocarray(handles, num_handles, sizeof(Handle));
+		handle_unused(num_handles - 1);
+	}
+
+	i = first_unused_handle;
+	first_unused_handle = handles[i].next_unused;
+
+	handles[i].use = use;
+	handles[i].dirp = dirp;
+	handles[i].fd = fd;
+	handles[i].flags = flags;
+	handles[i].name = xstrdup(name);
+	handles[i].bytes_read = handles[i].bytes_write = 0;
+
+	return i;
+}
+
+static int
+handle_is_ok(int i, int type)
+{
+	return i >= 0 && (u_int)i < num_handles && handles[i].use == type;
+}
+
+static int
+handle_to_string(int handle, u_char **stringp, int *hlenp)
+{
+	if (stringp == NULL || hlenp == NULL)
+		return -1;
+	*stringp = xmalloc(sizeof(int32_t));
+	put_u32(*stringp, handle);
+	*hlenp = sizeof(int32_t);
+	return 0;
+}
+
+static int
+handle_from_string(const u_char *handle, u_int hlen)
+{
+	int val;
+
+	if (hlen != sizeof(int32_t))
+		return -1;
+	val = get_u32(handle);
+	if (handle_is_ok(val, HANDLE_FILE) ||
+	    handle_is_ok(val, HANDLE_DIR))
+		return val;
+	return -1;
+}
+
+static char *
+handle_to_name(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_DIR)||
+	    handle_is_ok(handle, HANDLE_FILE))
+		return handles[handle].name;
+	return NULL;
+}
+
+static DIR *
+handle_to_dir(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_DIR))
+		return handles[handle].dirp;
+	return NULL;
+}
+
+static int
+handle_to_fd(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_FILE))
+		return handles[handle].fd;
+	return -1;
+}
+
+static int
+handle_to_flags(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_FILE))
+		return handles[handle].flags;
+	return 0;
+}
+
+static void
+handle_update_read(int handle, ssize_t bytes)
+{
+	if (handle_is_ok(handle, HANDLE_FILE) && bytes > 0)
+		handles[handle].bytes_read += bytes;
+}
+
+static void
+handle_update_write(int handle, ssize_t bytes)
+{
+	if (handle_is_ok(handle, HANDLE_FILE) && bytes > 0)
+		handles[handle].bytes_write += bytes;
+}
+
+static u_int64_t
+handle_bytes_read(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_FILE))
+		return (handles[handle].bytes_read);
+	return 0;
+}
+
+static u_int64_t
+handle_bytes_write(int handle)
+{
+	if (handle_is_ok(handle, HANDLE_FILE))
+		return (handles[handle].bytes_write);
+	return 0;
+}
+
+static int
+handle_close(int handle)
+{
+	int ret = -1;
+
+	if (handle_is_ok(handle, HANDLE_FILE)) {
+		ret = close(handles[handle].fd);
+		free(handles[handle].name);
+		handle_unused(handle);
+	} else if (handle_is_ok(handle, HANDLE_DIR)) {
+		ret = closedir(handles[handle].dirp);
+		free(handles[handle].name);
+		handle_unused(handle);
+	} else {
+		errno = ENOENT;
+	}
+	return ret;
+}
+
+static void
+handle_log_close(int handle, char *emsg)
+{
+	if (handle_is_ok(handle, HANDLE_FILE)) {
+		logit("%s%sclose \"%s\" bytes read %llu written %llu",
+		    emsg == NULL ? "" : emsg, emsg == NULL ? "" : " ",
+		    handle_to_name(handle),
+		    (unsigned long long)handle_bytes_read(handle),
+		    (unsigned long long)handle_bytes_write(handle));
+	} else {
+		logit("%s%sclosedir \"%s\"",
+		    emsg == NULL ? "" : emsg, emsg == NULL ? "" : " ",
+		    handle_to_name(handle));
+	}
+}
+
+static void
+handle_log_exit(void)
+{
+	u_int i;
+
+	for (i = 0; i < num_handles; i++)
+		if (handles[i].use != HANDLE_UNUSED)
+			handle_log_close(i, "forced");
+}
+
+static int
+get_handle(struct sshbuf *queue, int *hp)
+{
+	u_char *handle;
+	int r;
+	size_t hlen;
+
+	*hp = -1;
+	if ((r = sshbuf_get_string(queue, &handle, &hlen)) != 0)
+		return r;
+	if (hlen < 256)
+		*hp = handle_from_string(handle, hlen);
+	free(handle);
+	return 0;
+}
+
+/* send replies */
+
+static void
+send_msg(struct sshbuf *m)
+{
+	int r;
+
+	if ((r = sshbuf_put_stringb(oqueue, m)) != 0)
+		fatal_fr(r, "enqueue");
+	sshbuf_reset(m);
+}
+
+static const char *
+status_to_message(u_int32_t status)
+{
+	static const char * const status_messages[] = {
+		"Success",			/* SSH_FX_OK */
+		"End of file",			/* SSH_FX_EOF */
+		"No such file",			/* SSH_FX_NO_SUCH_FILE */
+		"Permission denied",		/* SSH_FX_PERMISSION_DENIED */
+		"Failure",			/* SSH_FX_FAILURE */
+		"Bad message",			/* SSH_FX_BAD_MESSAGE */
+		"No connection",		/* SSH_FX_NO_CONNECTION */
+		"Connection lost",		/* SSH_FX_CONNECTION_LOST */
+		"Operation unsupported",	/* SSH_FX_OP_UNSUPPORTED */
+		"Unknown error"			/* Others */
+	};
+	return (status_messages[MINIMUM(status,SSH2_FX_MAX)]);
+}
+
+static void
+send_status_errmsg(u_int32_t id, u_int32_t status, const char *errmsg)
+{
+	struct sshbuf *msg;
+	int r;
+
+	debug3("request %u: sent status %u", id, status);
+	if (log_level > SYSLOG_LEVEL_VERBOSE ||
+	    (status != SSH2_FX_OK && status != SSH2_FX_EOF))
+		logit("sent status %s", status_to_message(status));
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_STATUS)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = sshbuf_put_u32(msg, status)) != 0)
+		fatal_fr(r, "compose");
+	if (version >= 3) {
+		if ((r = sshbuf_put_cstring(msg, errmsg == NULL ?
+		    status_to_message(status) : errmsg)) != 0 ||
+		    (r = sshbuf_put_cstring(msg, "")) != 0)
+			fatal_fr(r, "compose message");
+	}
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+send_status(u_int32_t id, u_int32_t status)
+{
+	send_status_errmsg(id, status, NULL);
+}
+
+static void
+send_data_or_handle(char type, u_int32_t id, const u_char *data, int dlen)
+{
+	struct sshbuf *msg;
+	int r;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, type)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = sshbuf_put_string(msg, data, dlen)) != 0)
+		fatal_fr(r, "compose");
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+send_data(u_int32_t id, const u_char *data, int dlen)
+{
+	debug("request %u: sent data len %d", id, dlen);
+	send_data_or_handle(SSH2_FXP_DATA, id, data, dlen);
+}
+
+static void
+send_handle(u_int32_t id, int handle)
+{
+	u_char *string;
+	int hlen;
+
+	handle_to_string(handle, &string, &hlen);
+	debug("request %u: sent handle handle %d", id, handle);
+	send_data_or_handle(SSH2_FXP_HANDLE, id, string, hlen);
+	free(string);
+}
+
+static void
+send_names(u_int32_t id, int count, const Stat *stats)
+{
+	struct sshbuf *msg;
+	int i, r;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_NAME)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = sshbuf_put_u32(msg, count)) != 0)
+		fatal_fr(r, "compose");
+	debug("request %u: sent names count %d", id, count);
+	for (i = 0; i < count; i++) {
+		if ((r = sshbuf_put_cstring(msg, stats[i].name)) != 0 ||
+		    (r = sshbuf_put_cstring(msg, stats[i].long_name)) != 0 ||
+		    (r = encode_attrib(msg, &stats[i].attrib)) != 0)
+			fatal_fr(r, "compose filenames/attrib");
+	}
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+send_attrib(u_int32_t id, const Attrib *a)
+{
+	struct sshbuf *msg;
+	int r;
+
+	debug("request %u: sent attrib have 0x%x", id, a->flags);
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_ATTRS)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = encode_attrib(msg, a)) != 0)
+		fatal_fr(r, "compose");
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+send_statvfs(u_int32_t id, struct statvfs *st)
+{
+	struct sshbuf *msg;
+	u_int64_t flag;
+	int r;
+
+	flag = (st->f_flag & ST_RDONLY) ? SSH2_FXE_STATVFS_ST_RDONLY : 0;
+	flag |= (st->f_flag & ST_NOSUID) ? SSH2_FXE_STATVFS_ST_NOSUID : 0;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_EXTENDED_REPLY)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_bsize)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_frsize)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_blocks)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_bfree)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_bavail)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_files)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_ffree)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_favail)) != 0 ||
+	    (r = sshbuf_put_u64(msg, FSID_TO_ULONG(st->f_fsid))) != 0 ||
+	    (r = sshbuf_put_u64(msg, flag)) != 0 ||
+	    (r = sshbuf_put_u64(msg, st->f_namemax)) != 0)
+		fatal_fr(r, "compose");
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+/*
+ * Prepare SSH2_FXP_VERSION extension advertisement for a single extension.
+ * The extension is checked for permission prior to advertisement.
+ */
+static int
+compose_extension(struct sshbuf *msg, const char *name, const char *ver)
+{
+	int r;
+	const struct sftp_handler *exthnd;
+
+	if ((exthnd = extended_handler_byname(name)) == NULL)
+		fatal_f("internal error: no handler for %s", name);
+	if (!request_permitted(exthnd)) {
+		debug2_f("refusing to advertise disallowed extension %s", name);
+		return 0;
+	}
+	if ((r = sshbuf_put_cstring(msg, name)) != 0 ||
+	    (r = sshbuf_put_cstring(msg, ver)) != 0)
+		fatal_fr(r, "compose %s", name);
+	return 0;
+}
+
+/* parse incoming */
+
+static void
+process_init(void)
+{
+	struct sshbuf *msg;
+	int r;
+
+	if ((r = sshbuf_get_u32(iqueue, &version)) != 0)
+		fatal_fr(r, "parse");
+	verbose("received client version %u", version);
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_VERSION)) != 0 ||
+	    (r = sshbuf_put_u32(msg, SSH2_FILEXFER_VERSION)) != 0)
+		fatal_fr(r, "compose");
+
+	 /* extension advertisements */
+	compose_extension(msg, "posix-rename@openssh.com", "1");
+	compose_extension(msg, "statvfs@openssh.com", "2");
+	compose_extension(msg, "fstatvfs@openssh.com", "2");
+	compose_extension(msg, "hardlink@openssh.com", "1");
+	compose_extension(msg, "fsync@openssh.com", "1");
+	compose_extension(msg, "lsetstat@openssh.com", "1");
+	compose_extension(msg, "limits@openssh.com", "1");
+	compose_extension(msg, "expand-path@openssh.com", "1");
+	compose_extension(msg, "copy-data", "1");
+	compose_extension(msg, "home-directory", "1");
+	compose_extension(msg, "users-groups-by-id@openssh.com", "1");
+
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+process_open(u_int32_t id)
+{
+	u_int32_t pflags;
+	Attrib a;
+	char *name;
+	int r, handle, fd, flags, mode, status = SSH2_FX_FAILURE;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(iqueue, &pflags)) != 0 || /* portable flags */
+	    (r = decode_attrib(iqueue, &a)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: open flags %d", id, pflags);
+	flags = flags_from_portable(pflags);
+	mode = (a.flags & SSH2_FILEXFER_ATTR_PERMISSIONS) ? a.perm : 0666;
+	logit("open \"%s\" flags %s mode 0%o",
+	    name, string_from_portable(pflags), mode);
+	if (readonly &&
+	    ((flags & O_ACCMODE) != O_RDONLY ||
+	    (flags & (O_CREAT|O_TRUNC)) != 0)) {
+		verbose("Refusing open request in read-only mode");
+		status = SSH2_FX_PERMISSION_DENIED;
+	} else {
+		fd = open(name, flags, mode);
+		if (fd == -1) {
+			status = errno_to_portable(errno);
+		} else {
+			handle = handle_new(HANDLE_FILE, name, fd, flags, NULL);
+			if (handle < 0) {
+				close(fd);
+			} else {
+				send_handle(id, handle);
+				status = SSH2_FX_OK;
+			}
+		}
+	}
+	if (status != SSH2_FX_OK)
+		send_status(id, status);
+	free(name);
+}
+
+static void
+process_close(u_int32_t id)
+{
+	int r, handle, ret, status = SSH2_FX_FAILURE;
+
+	if ((r = get_handle(iqueue, &handle)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: close handle %u", id, handle);
+	handle_log_close(handle, NULL);
+	ret = handle_close(handle);
+	status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+}
+
+static void
+process_read(u_int32_t id)
+{
+	static u_char *buf;
+	static size_t buflen;
+	u_int32_t len;
+	int r, handle, fd, ret, status = SSH2_FX_FAILURE;
+	u_int64_t off;
+
+	if ((r = get_handle(iqueue, &handle)) != 0 ||
+	    (r = sshbuf_get_u64(iqueue, &off)) != 0 ||
+	    (r = sshbuf_get_u32(iqueue, &len)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: read \"%s\" (handle %d) off %llu len %u",
+	    id, handle_to_name(handle), handle, (unsigned long long)off, len);
+	if ((fd = handle_to_fd(handle)) == -1)
+		goto out;
+	if (len > SFTP_MAX_READ_LENGTH) {
+		debug2("read change len %u to %u", len, SFTP_MAX_READ_LENGTH);
+		len = SFTP_MAX_READ_LENGTH;
+	}
+	if (len > buflen) {
+		debug3_f("allocate %zu => %u", buflen, len);
+		if ((buf = realloc(NULL, len)) == NULL)
+			fatal_f("realloc failed");
+		buflen = len;
+	}
+	if (lseek(fd, off, SEEK_SET) == -1) {
+		status = errno_to_portable(errno);
+		error_f("seek \"%.100s\": %s", handle_to_name(handle),
+		    strerror(errno));
+		goto out;
+	}
+	if (len == 0) {
+		/* weird, but not strictly disallowed */
+		ret = 0;
+	} else if ((ret = read(fd, buf, len)) == -1) {
+		status = errno_to_portable(errno);
+		error_f("read \"%.100s\": %s", handle_to_name(handle),
+		    strerror(errno));
+		goto out;
+	} else if (ret == 0) {
+		status = SSH2_FX_EOF;
+		goto out;
+	}
+	send_data(id, buf, ret);
+	handle_update_read(handle, ret);
+	/* success */
+	status = SSH2_FX_OK;
+ out:
+	if (status != SSH2_FX_OK)
+		send_status(id, status);
+}
+
+static void
+process_write(u_int32_t id)
+{
+	u_int64_t off;
+	size_t len;
+	int r, handle, fd, ret, status;
+	u_char *data;
+
+	if ((r = get_handle(iqueue, &handle)) != 0 ||
+	    (r = sshbuf_get_u64(iqueue, &off)) != 0 ||
+	    (r = sshbuf_get_string(iqueue, &data, &len)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: write \"%s\" (handle %d) off %llu len %zu",
+	    id, handle_to_name(handle), handle, (unsigned long long)off, len);
+	fd = handle_to_fd(handle);
+
+	if (fd < 0)
+		status = SSH2_FX_FAILURE;
+	else {
+		if (!(handle_to_flags(handle) & O_APPEND) &&
+		    lseek(fd, off, SEEK_SET) == -1) {
+			status = errno_to_portable(errno);
+			error_f("seek \"%.100s\": %s", handle_to_name(handle),
+			    strerror(errno));
+		} else {
+/* XXX ATOMICIO ? */
+			ret = write(fd, data, len);
+			if (ret == -1) {
+				status = errno_to_portable(errno);
+				error_f("write \"%.100s\": %s",
+				    handle_to_name(handle), strerror(errno));
+			} else if ((size_t)ret == len) {
+				status = SSH2_FX_OK;
+				handle_update_write(handle, ret);
+			} else {
+				debug2_f("nothing at all written");
+				status = SSH2_FX_FAILURE;
+			}
+		}
+	}
+	send_status(id, status);
+	free(data);
+}
+
+static void
+process_do_stat(u_int32_t id, int do_lstat)
+{
+	Attrib a;
+	struct stat st;
+	char *name;
+	int r, status = SSH2_FX_FAILURE;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: %sstat", id, do_lstat ? "l" : "");
+	verbose("%sstat name \"%s\"", do_lstat ? "l" : "", name);
+	r = do_lstat ? lstat(name, &st) : stat(name, &st);
+	if (r == -1) {
+		status = errno_to_portable(errno);
+	} else {
+		stat_to_attrib(&st, &a);
+		send_attrib(id, &a);
+		status = SSH2_FX_OK;
+	}
+	if (status != SSH2_FX_OK)
+		send_status(id, status);
+	free(name);
+}
+
+static void
+process_stat(u_int32_t id)
+{
+	process_do_stat(id, 0);
+}
+
+static void
+process_lstat(u_int32_t id)
+{
+	process_do_stat(id, 1);
+}
+
+static void
+process_fstat(u_int32_t id)
+{
+	Attrib a;
+	struct stat st;
+	int fd, r, handle, status = SSH2_FX_FAILURE;
+
+	if ((r = get_handle(iqueue, &handle)) != 0)
+		fatal_fr(r, "parse");
+	debug("request %u: fstat \"%s\" (handle %u)",
+	    id, handle_to_name(handle), handle);
+	fd = handle_to_fd(handle);
+	if (fd >= 0) {
+		r = fstat(fd, &st);
+		if (r == -1) {
+			status = errno_to_portable(errno);
+		} else {
+			stat_to_attrib(&st, &a);
+			send_attrib(id, &a);
+			status = SSH2_FX_OK;
+		}
+	}
+	if (status != SSH2_FX_OK)
+		send_status(id, status);
+}
+
+static struct timeval *
+attrib_to_tv(const Attrib *a)
+{
+	static struct timeval tv[2];
+
+	tv[0].tv_sec = a->atime;
+	tv[0].tv_usec = 0;
+	tv[1].tv_sec = a->mtime;
+	tv[1].tv_usec = 0;
+	return tv;
+}
+
+static struct timespec *
+attrib_to_ts(const Attrib *a)
+{
+	static struct timespec ts[2];
+
+	ts[0].tv_sec = a->atime;
+	ts[0].tv_nsec = 0;
+	ts[1].tv_sec = a->mtime;
+	ts[1].tv_nsec = 0;
+	return ts;
+}
+
+static void
+process_setstat(u_int32_t id)
+{
+	Attrib a;
+	char *name;
+	int r, status = SSH2_FX_OK;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
+	    (r = decode_attrib(iqueue, &a)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: setstat name \"%s\"", id, name);
+	if (a.flags & SSH2_FILEXFER_ATTR_SIZE) {
+		logit("set \"%s\" size %llu",
+		    name, (unsigned long long)a.size);
+		r = truncate(name, a.size);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_PERMISSIONS) {
+		logit("set \"%s\" mode %04o", name, a.perm);
+		r = chmod(name, a.perm & 07777);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_ACMODTIME) {
+		char buf[64];
+		time_t t = a.mtime;
+
+		strftime(buf, sizeof(buf), "%Y%m%d-%H:%M:%S",
+		    localtime(&t));
+		logit("set \"%s\" modtime %s", name, buf);
+		r = utimes(name, attrib_to_tv(&a));
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_UIDGID) {
+		logit("set \"%s\" owner %lu group %lu", name,
+		    (u_long)a.uid, (u_long)a.gid);
+		r = chown(name, a.uid, a.gid);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	send_status(id, status);
+	free(name);
+}
+
+static void
+process_fsetstat(u_int32_t id)
+{
+	Attrib a;
+	int handle, fd, r;
+	int status = SSH2_FX_OK;
+
+	if ((r = get_handle(iqueue, &handle)) != 0 ||
+	    (r = decode_attrib(iqueue, &a)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: fsetstat handle %d", id, handle);
+	fd = handle_to_fd(handle);
+	if (fd < 0)
+		status = SSH2_FX_FAILURE;
+	else {
+		char *name = handle_to_name(handle);
+
+		if (a.flags & SSH2_FILEXFER_ATTR_SIZE) {
+			logit("set \"%s\" size %llu",
+			    name, (unsigned long long)a.size);
+			r = ftruncate(fd, a.size);
+			if (r == -1)
+				status = errno_to_portable(errno);
+		}
+		if (a.flags & SSH2_FILEXFER_ATTR_PERMISSIONS) {
+			logit("set \"%s\" mode %04o", name, a.perm);
+#ifdef HAVE_FCHMOD
+			r = fchmod(fd, a.perm & 07777);
+#else
+			r = chmod(name, a.perm & 07777);
+#endif
+			if (r == -1)
+				status = errno_to_portable(errno);
+		}
+		if (a.flags & SSH2_FILEXFER_ATTR_ACMODTIME) {
+			char buf[64];
+			time_t t = a.mtime;
+
+			strftime(buf, sizeof(buf), "%Y%m%d-%H:%M:%S",
+			    localtime(&t));
+			logit("set \"%s\" modtime %s", name, buf);
+#ifdef HAVE_FUTIMES
+			r = futimes(fd, attrib_to_tv(&a));
+#else
+			r = utimes(name, attrib_to_tv(&a));
+#endif
+			if (r == -1)
+				status = errno_to_portable(errno);
+		}
+		if (a.flags & SSH2_FILEXFER_ATTR_UIDGID) {
+			logit("set \"%s\" owner %lu group %lu", name,
+			    (u_long)a.uid, (u_long)a.gid);
+#ifdef HAVE_FCHOWN
+			r = fchown(fd, a.uid, a.gid);
+#else
+			r = chown(name, a.uid, a.gid);
+#endif
+			if (r == -1)
+				status = errno_to_portable(errno);
+		}
+	}
+	send_status(id, status);
+}
+
+static void
+process_opendir(u_int32_t id)
+{
+	DIR *dirp = NULL;
+	char *path;
+	int r, handle, status = SSH2_FX_FAILURE;
+
+	if ((r = sshbuf_get_cstring(iqueue, &path, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: opendir", id);
+	logit("opendir \"%s\"", path);
+	dirp = opendir(path);
+	if (dirp == NULL) {
+		status = errno_to_portable(errno);
+	} else {
+		handle = handle_new(HANDLE_DIR, path, 0, 0, dirp);
+		if (handle < 0) {
+			closedir(dirp);
+		} else {
+			send_handle(id, handle);
+			status = SSH2_FX_OK;
+		}
+
+	}
+	if (status != SSH2_FX_OK)
+		send_status(id, status);
+	free(path);
+}
+
+static void
+process_readdir(u_int32_t id)
+{
+	DIR *dirp;
+	struct dirent *dp;
+	char *path;
+	int r, handle;
+
+	if ((r = get_handle(iqueue, &handle)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: readdir \"%s\" (handle %d)", id,
+	    handle_to_name(handle), handle);
+	dirp = handle_to_dir(handle);
+	path = handle_to_name(handle);
+	if (dirp == NULL || path == NULL) {
+		send_status(id, SSH2_FX_FAILURE);
+	} else {
+		struct stat st;
+		char pathname[PATH_MAX];
+		Stat *stats;
+		int nstats = 10, count = 0, i;
+
+		stats = xcalloc(nstats, sizeof(Stat));
+		while ((dp = readdir(dirp)) != NULL) {
+			if (count >= nstats) {
+				nstats *= 2;
+				stats = xreallocarray(stats, nstats, sizeof(Stat));
+			}
+/* XXX OVERFLOW ? */
+			snprintf(pathname, sizeof pathname, "%s%s%s", path,
+			    strcmp(path, "/") ? "/" : "", dp->d_name);
+			if (lstat(pathname, &st) == -1)
+				continue;
+			stat_to_attrib(&st, &(stats[count].attrib));
+			stats[count].name = xstrdup(dp->d_name);
+			stats[count].long_name = ls_file(dp->d_name, &st,
+			    0, 0, NULL, NULL);
+			count++;
+			/* send up to 100 entries in one message */
+			/* XXX check packet size instead */
+			if (count == 100)
+				break;
+		}
+		if (count > 0) {
+			send_names(id, count, stats);
+			for (i = 0; i < count; i++) {
+				free(stats[i].name);
+				free(stats[i].long_name);
+			}
+		} else {
+			send_status(id, SSH2_FX_EOF);
+		}
+		free(stats);
+	}
+}
+
+static void
+process_remove(u_int32_t id)
+{
+	char *name;
+	int r, status = SSH2_FX_FAILURE;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: remove", id);
+	logit("remove name \"%s\"", name);
+	r = unlink(name);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(name);
+}
+
+static void
+process_mkdir(u_int32_t id)
+{
+	Attrib a;
+	char *name;
+	int r, mode, status = SSH2_FX_FAILURE;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
+	    (r = decode_attrib(iqueue, &a)) != 0)
+		fatal_fr(r, "parse");
+
+	mode = (a.flags & SSH2_FILEXFER_ATTR_PERMISSIONS) ?
+	    a.perm & 07777 : 0777;
+	debug3("request %u: mkdir", id);
+	logit("mkdir name \"%s\" mode 0%o", name, mode);
+	r = mkdir(name, mode);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(name);
+}
+
+static void
+process_rmdir(u_int32_t id)
+{
+	char *name;
+	int r, status;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: rmdir", id);
+	logit("rmdir name \"%s\"", name);
+	r = rmdir(name);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(name);
+}
+
+static void
+process_realpath(u_int32_t id)
+{
+	char resolvedname[PATH_MAX];
+	char *path;
+	int r;
+
+	if ((r = sshbuf_get_cstring(iqueue, &path, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	if (path[0] == '\0') {
+		free(path);
+		path = xstrdup(".");
+	}
+	debug3("request %u: realpath", id);
+	verbose("realpath \"%s\"", path);
+	if (sftp_realpath(path, resolvedname) == NULL) {
+		send_status(id, errno_to_portable(errno));
+	} else {
+		Stat s;
+		attrib_clear(&s.attrib);
+		s.name = s.long_name = resolvedname;
+		send_names(id, 1, &s);
+	}
+	free(path);
+}
+
+static void
+process_rename(u_int32_t id)
+{
+	char *oldpath, *newpath;
+	int r, status;
+	struct stat sb;
+
+	if ((r = sshbuf_get_cstring(iqueue, &oldpath, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(iqueue, &newpath, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: rename", id);
+	logit("rename old \"%s\" new \"%s\"", oldpath, newpath);
+	status = SSH2_FX_FAILURE;
+	if (lstat(oldpath, &sb) == -1)
+		status = errno_to_portable(errno);
+	else if (S_ISREG(sb.st_mode)) {
+		/* Race-free rename of regular files */
+		if (link(oldpath, newpath) == -1) {
+			if (errno == EOPNOTSUPP || errno == ENOSYS
+#ifdef EXDEV
+			    || errno == EXDEV
+#endif
+#ifdef LINK_OPNOTSUPP_ERRNO
+			    || errno == LINK_OPNOTSUPP_ERRNO
+#endif
+			    ) {
+				struct stat st;
+
+				/*
+				 * fs doesn't support links, so fall back to
+				 * stat+rename.  This is racy.
+				 */
+				if (stat(newpath, &st) == -1) {
+					if (rename(oldpath, newpath) == -1)
+						status =
+						    errno_to_portable(errno);
+					else
+						status = SSH2_FX_OK;
+				}
+			} else {
+				status = errno_to_portable(errno);
+			}
+		} else if (unlink(oldpath) == -1) {
+			status = errno_to_portable(errno);
+			/* clean spare link */
+			unlink(newpath);
+		} else
+			status = SSH2_FX_OK;
+	} else if (stat(newpath, &sb) == -1) {
+		if (rename(oldpath, newpath) == -1)
+			status = errno_to_portable(errno);
+		else
+			status = SSH2_FX_OK;
+	}
+	send_status(id, status);
+	free(oldpath);
+	free(newpath);
+}
+
+static void
+process_readlink(u_int32_t id)
+{
+	int r, len;
+	char buf[PATH_MAX];
+	char *path;
+
+	if ((r = sshbuf_get_cstring(iqueue, &path, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: readlink", id);
+	verbose("readlink \"%s\"", path);
+	if ((len = readlink(path, buf, sizeof(buf) - 1)) == -1)
+		send_status(id, errno_to_portable(errno));
+	else {
+		Stat s;
+
+		buf[len] = '\0';
+		attrib_clear(&s.attrib);
+		s.name = s.long_name = buf;
+		send_names(id, 1, &s);
+	}
+	free(path);
+}
+
+static void
+process_symlink(u_int32_t id)
+{
+	char *oldpath, *newpath;
+	int r, status;
+
+	if ((r = sshbuf_get_cstring(iqueue, &oldpath, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(iqueue, &newpath, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: symlink", id);
+	logit("symlink old \"%s\" new \"%s\"", oldpath, newpath);
+	/* this will fail if 'newpath' exists */
+	r = symlink(oldpath, newpath);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(oldpath);
+	free(newpath);
+}
+
+static void
+process_extended_posix_rename(u_int32_t id)
+{
+	char *oldpath, *newpath;
+	int r, status;
+
+	if ((r = sshbuf_get_cstring(iqueue, &oldpath, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(iqueue, &newpath, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: posix-rename", id);
+	logit("posix-rename old \"%s\" new \"%s\"", oldpath, newpath);
+	r = rename(oldpath, newpath);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(oldpath);
+	free(newpath);
+}
+
+static void
+process_extended_statvfs(u_int32_t id)
+{
+	char *path;
+	struct statvfs st;
+	int r;
+
+	if ((r = sshbuf_get_cstring(iqueue, &path, NULL)) != 0)
+		fatal_fr(r, "parse");
+	debug3("request %u: statvfs", id);
+	logit("statvfs \"%s\"", path);
+
+	if (statvfs(path, &st) != 0)
+		send_status(id, errno_to_portable(errno));
+	else
+		send_statvfs(id, &st);
+	free(path);
+}
+
+static void
+process_extended_fstatvfs(u_int32_t id)
+{
+	int r, handle, fd;
+	struct statvfs st;
+
+	if ((r = get_handle(iqueue, &handle)) != 0)
+		fatal_fr(r, "parse");
+	debug("request %u: fstatvfs \"%s\" (handle %u)",
+	    id, handle_to_name(handle), handle);
+	if ((fd = handle_to_fd(handle)) < 0) {
+		send_status(id, SSH2_FX_FAILURE);
+		return;
+	}
+	if (fstatvfs(fd, &st) != 0)
+		send_status(id, errno_to_portable(errno));
+	else
+		send_statvfs(id, &st);
+}
+
+static void
+process_extended_hardlink(u_int32_t id)
+{
+	char *oldpath, *newpath;
+	int r, status;
+
+	if ((r = sshbuf_get_cstring(iqueue, &oldpath, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(iqueue, &newpath, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: hardlink", id);
+	logit("hardlink old \"%s\" new \"%s\"", oldpath, newpath);
+	r = link(oldpath, newpath);
+	status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	send_status(id, status);
+	free(oldpath);
+	free(newpath);
+}
+
+static void
+process_extended_fsync(u_int32_t id)
+{
+	int handle, fd, r, status = SSH2_FX_OP_UNSUPPORTED;
+
+	if ((r = get_handle(iqueue, &handle)) != 0)
+		fatal_fr(r, "parse");
+	debug3("request %u: fsync (handle %u)", id, handle);
+	verbose("fsync \"%s\"", handle_to_name(handle));
+	if ((fd = handle_to_fd(handle)) < 0)
+		status = SSH2_FX_NO_SUCH_FILE;
+	else if (handle_is_ok(handle, HANDLE_FILE)) {
+		r = fsync(fd);
+		status = (r == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
+	}
+	send_status(id, status);
+}
+
+static void
+process_extended_lsetstat(u_int32_t id)
+{
+	Attrib a;
+	char *name;
+	int r, status = SSH2_FX_OK;
+
+	if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
+	    (r = decode_attrib(iqueue, &a)) != 0)
+		fatal_fr(r, "parse");
+
+	debug("request %u: lsetstat name \"%s\"", id, name);
+	if (a.flags & SSH2_FILEXFER_ATTR_SIZE) {
+		/* nonsensical for links */
+		status = SSH2_FX_BAD_MESSAGE;
+		goto out;
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_PERMISSIONS) {
+		logit("set \"%s\" mode %04o", name, a.perm);
+		r = fchmodat(AT_FDCWD, name,
+		    a.perm & 07777, AT_SYMLINK_NOFOLLOW);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_ACMODTIME) {
+		char buf[64];
+		time_t t = a.mtime;
+
+		strftime(buf, sizeof(buf), "%Y%m%d-%H:%M:%S",
+		    localtime(&t));
+		logit("set \"%s\" modtime %s", name, buf);
+		r = utimensat(AT_FDCWD, name,
+		    attrib_to_ts(&a), AT_SYMLINK_NOFOLLOW);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+	if (a.flags & SSH2_FILEXFER_ATTR_UIDGID) {
+		logit("set \"%s\" owner %lu group %lu", name,
+		    (u_long)a.uid, (u_long)a.gid);
+		r = fchownat(AT_FDCWD, name, a.uid, a.gid,
+		    AT_SYMLINK_NOFOLLOW);
+		if (r == -1)
+			status = errno_to_portable(errno);
+	}
+ out:
+	send_status(id, status);
+	free(name);
+}
+
+static void
+process_extended_limits(u_int32_t id)
+{
+	struct sshbuf *msg;
+	int r;
+	uint64_t nfiles = 0;
+#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_NOFILE)
+	struct rlimit rlim;
+#endif
+
+	debug("request %u: limits", id);
+
+#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_NOFILE)
+	if (getrlimit(RLIMIT_NOFILE, &rlim) != -1 && rlim.rlim_cur > 5)
+		nfiles = rlim.rlim_cur - 5; /* stdio(3) + syslog + spare */
+#endif
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_EXTENDED_REPLY)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    /* max-packet-length */
+	    (r = sshbuf_put_u64(msg, SFTP_MAX_MSG_LENGTH)) != 0 ||
+	    /* max-read-length */
+	    (r = sshbuf_put_u64(msg, SFTP_MAX_READ_LENGTH)) != 0 ||
+	    /* max-write-length */
+	    (r = sshbuf_put_u64(msg, SFTP_MAX_MSG_LENGTH - 1024)) != 0 ||
+	    /* max-open-handles */
+	    (r = sshbuf_put_u64(msg, nfiles)) != 0)
+		fatal_fr(r, "compose");
+	send_msg(msg);
+	sshbuf_free(msg);
+}
+
+static void
+process_extended_expand(u_int32_t id)
+{
+	char cwd[PATH_MAX], resolvedname[PATH_MAX];
+	char *path, *npath;
+	int r;
+	Stat s;
+
+	if ((r = sshbuf_get_cstring(iqueue, &path, NULL)) != 0)
+		fatal_fr(r, "parse");
+	if (getcwd(cwd, sizeof(cwd)) == NULL) {
+		send_status(id, errno_to_portable(errno));
+		goto out;
+	}
+
+	debug3("request %u: expand, original \"%s\"", id, path);
+	if (path[0] == '\0') {
+		/* empty path */
+		free(path);
+		path = xstrdup(".");
+	} else if (*path == '~') {
+		/* ~ expand path */
+		/* Special-case for "~" and "~/" to respect homedir flag */
+		if (strcmp(path, "~") == 0) {
+			free(path);
+			path = xstrdup(cwd);
+		} else if (strncmp(path, "~/", 2) == 0) {
+			npath = xstrdup(path + 2);
+			free(path);
+			xasprintf(&path, "%s/%s", cwd, npath);
+			free(npath);
+		} else {
+			/* ~user expansions */
+			if (tilde_expand(path, pw->pw_uid, &npath) != 0) {
+				send_status_errmsg(id,
+				    errno_to_portable(ENOENT), "no such user");
+				goto out;
+			}
+			free(path);
+			path = npath;
+		}
+	} else if (*path != '/') {
+		/* relative path */
+		xasprintf(&npath, "%s/%s", cwd, path);
+		free(path);
+		path = npath;
+	}
+	verbose("expand \"%s\"", path);
+	if (sftp_realpath(path, resolvedname) == NULL) {
+		send_status(id, errno_to_portable(errno));
+		goto out;
+	}
+	attrib_clear(&s.attrib);
+	s.name = s.long_name = resolvedname;
+	send_names(id, 1, &s);
+ out:
+	free(path);
+}
+
+static void
+process_extended_copy_data(u_int32_t id)
+{
+	u_char buf[64*1024];
+	int read_handle, read_fd, write_handle, write_fd;
+	u_int64_t len, read_off, read_len, write_off;
+	int r, copy_until_eof, status = SSH2_FX_OP_UNSUPPORTED;
+	size_t ret;
+
+	if ((r = get_handle(iqueue, &read_handle)) != 0 ||
+	    (r = sshbuf_get_u64(iqueue, &read_off)) != 0 ||
+	    (r = sshbuf_get_u64(iqueue, &read_len)) != 0 ||
+	    (r = get_handle(iqueue, &write_handle)) != 0 ||
+	    (r = sshbuf_get_u64(iqueue, &write_off)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	debug("request %u: copy-data from \"%s\" (handle %d) off %llu len %llu "
+	    "to \"%s\" (handle %d) off %llu",
+	    id, handle_to_name(read_handle), read_handle,
+	    (unsigned long long)read_off, (unsigned long long)read_len,
+	    handle_to_name(write_handle), write_handle,
+	    (unsigned long long)write_off);
+
+	/* For read length of 0, we read until EOF. */
+	if (read_len == 0) {
+		read_len = (u_int64_t)-1 - read_off;
+		copy_until_eof = 1;
+	} else
+		copy_until_eof = 0;
+
+	read_fd = handle_to_fd(read_handle);
+	write_fd = handle_to_fd(write_handle);
+
+	/* Disallow reading & writing to the same handle or same path or dirs */
+	if (read_handle == write_handle || read_fd < 0 || write_fd < 0 ||
+	    !strcmp(handle_to_name(read_handle), handle_to_name(write_handle))) {
+		status = SSH2_FX_FAILURE;
+		goto out;
+	}
+
+	if (lseek(read_fd, read_off, SEEK_SET) < 0) {
+		status = errno_to_portable(errno);
+		error("%s: read_seek failed", __func__);
+		goto out;
+	}
+
+	if ((handle_to_flags(write_handle) & O_APPEND) == 0 &&
+	    lseek(write_fd, write_off, SEEK_SET) < 0) {
+		status = errno_to_portable(errno);
+		error("%s: write_seek failed", __func__);
+		goto out;
+	}
+
+	/* Process the request in chunks. */
+	while (read_len > 0 || copy_until_eof) {
+		len = MINIMUM(sizeof(buf), read_len);
+		read_len -= len;
+
+		ret = atomicio(read, read_fd, buf, len);
+		if (ret == 0 && errno == EPIPE) {
+			status = copy_until_eof ? SSH2_FX_OK : SSH2_FX_EOF;
+			break;
+		} else if (ret == 0) {
+			status = errno_to_portable(errno);
+			error("%s: read failed: %s", __func__, strerror(errno));
+			break;
+		}
+		len = ret;
+		handle_update_read(read_handle, len);
+
+		ret = atomicio(vwrite, write_fd, buf, len);
+		if (ret != len) {
+			status = errno_to_portable(errno);
+			error("%s: write failed: %llu != %llu: %s", __func__,
+			    (unsigned long long)ret, (unsigned long long)len,
+			    strerror(errno));
+			break;
+		}
+		handle_update_write(write_handle, len);
+	}
+
+	if (read_len == 0)
+		status = SSH2_FX_OK;
+
+ out:
+	send_status(id, status);
+}
+
+static void
+process_extended_home_directory(u_int32_t id)
+{
+	char *username;
+	struct passwd *user_pw;
+	int r;
+	Stat s;
+
+	if ((r = sshbuf_get_cstring(iqueue, &username, NULL)) != 0)
+		fatal_fr(r, "parse");
+
+	debug3("request %u: home-directory \"%s\"", id, username);
+	if ((user_pw = getpwnam(username)) == NULL) {
+		send_status(id, SSH2_FX_FAILURE);
+		goto out;
+	}
+
+	verbose("home-directory \"%s\"", pw->pw_dir);
+	attrib_clear(&s.attrib);
+	s.name = s.long_name = pw->pw_dir;
+	send_names(id, 1, &s);
+ out:
+	free(username);
+}
+
+static void
+process_extended_get_users_groups_by_id(u_int32_t id)
+{
+	struct passwd *user_pw;
+	struct group *gr;
+	struct sshbuf *uids, *gids, *usernames, *groupnames, *msg;
+	int r;
+	u_int n, nusers = 0, ngroups = 0;
+	const char *name;
+
+	if ((usernames = sshbuf_new()) == NULL ||
+	    (groupnames = sshbuf_new()) == NULL ||
+	    (msg = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((r = sshbuf_froms(iqueue, &uids)) != 0 ||
+	    (r = sshbuf_froms(iqueue, &gids)) != 0)
+		fatal_fr(r, "parse");
+	debug_f("uids len = %zu, gids len = %zu",
+	    sshbuf_len(uids), sshbuf_len(gids));
+	while (sshbuf_len(uids) != 0) {
+		if ((r = sshbuf_get_u32(uids, &n)) != 0)
+			fatal_fr(r, "parse inner uid");
+		user_pw = getpwuid((uid_t)n);
+		name = user_pw == NULL ? "" : user_pw->pw_name;
+		debug3_f("uid %u => \"%s\"", n, name);
+		if ((r = sshbuf_put_cstring(usernames, name)) != 0)
+			fatal_fr(r, "assemble uid reply");
+		nusers++;
+	}
+	while (sshbuf_len(gids) != 0) {
+		if ((r = sshbuf_get_u32(gids, &n)) != 0)
+			fatal_fr(r, "parse inner gid");
+		gr = getgrgid((gid_t)n);
+		name = gr == NULL ? "" : gr->gr_name;
+		debug3_f("gid %u => \"%s\"", n, name);
+		if ((r = sshbuf_put_cstring(groupnames, name)) != 0)
+			fatal_fr(r, "assemble gid reply");
+		nusers++;
+	}
+	verbose("users-groups-by-id: %u users, %u groups", nusers, ngroups);
+
+	if ((r = sshbuf_put_u8(msg, SSH2_FXP_EXTENDED_REPLY)) != 0 ||
+	    (r = sshbuf_put_u32(msg, id)) != 0 ||
+	    (r = sshbuf_put_stringb(msg, usernames)) != 0 ||
+	    (r = sshbuf_put_stringb(msg, groupnames)) != 0)
+		fatal_fr(r, "compose");
+	send_msg(msg);
+
+	sshbuf_free(uids);
+	sshbuf_free(gids);
+	sshbuf_free(usernames);
+	sshbuf_free(groupnames);
+	sshbuf_free(msg);
+}
+
+static void
+process_extended(u_int32_t id)
+{
+	char *request;
+	int r;
+	const struct sftp_handler *exthand;
+
+	if ((r = sshbuf_get_cstring(iqueue, &request, NULL)) != 0)
+		fatal_fr(r, "parse");
+	if ((exthand = extended_handler_byname(request)) == NULL) {
+		error("Unknown extended request \"%.100s\"", request);
+		send_status(id, SSH2_FX_OP_UNSUPPORTED);	/* MUST */
+	} else {
+		if (!request_permitted(exthand))
+			send_status(id, SSH2_FX_PERMISSION_DENIED);
+		else
+			exthand->handler(id);
+	}
+	free(request);
+}
+
+/* stolen from ssh-agent */
+
+static void
+process(void)
+{
+	u_int msg_len;
+	u_int buf_len;
+	u_int consumed;
+	u_char type;
+	const u_char *cp;
+	int i, r;
+	u_int32_t id;
+
+	buf_len = sshbuf_len(iqueue);
+	if (buf_len < 5)
+		return;		/* Incomplete message. */
+	cp = sshbuf_ptr(iqueue);
+	msg_len = get_u32(cp);
+	if (msg_len > SFTP_MAX_MSG_LENGTH) {
+		error("bad message from %s local user %s",
+		    client_addr, pw->pw_name);
+		sftp_server_cleanup_exit(11);
+	}
+	if (buf_len < msg_len + 4)
+		return;
+	if ((r = sshbuf_consume(iqueue, 4)) != 0)
+		fatal_fr(r, "consume");
+	buf_len -= 4;
+	if ((r = sshbuf_get_u8(iqueue, &type)) != 0)
+		fatal_fr(r, "parse type");
+
+	switch (type) {
+	case SSH2_FXP_INIT:
+		process_init();
+		init_done = 1;
+		break;
+	case SSH2_FXP_EXTENDED:
+		if (!init_done)
+			fatal("Received extended request before init");
+		if ((r = sshbuf_get_u32(iqueue, &id)) != 0)
+			fatal_fr(r, "parse extended ID");
+		process_extended(id);
+		break;
+	default:
+		if (!init_done)
+			fatal("Received %u request before init", type);
+		if ((r = sshbuf_get_u32(iqueue, &id)) != 0)
+			fatal_fr(r, "parse ID");
+		for (i = 0; handlers[i].handler != NULL; i++) {
+			if (type == handlers[i].type) {
+				if (!request_permitted(&handlers[i])) {
+					send_status(id,
+					    SSH2_FX_PERMISSION_DENIED);
+				} else {
+					handlers[i].handler(id);
+				}
+				break;
+			}
+		}
+		if (handlers[i].handler == NULL)
+			error("Unknown message %u", type);
+	}
+	/* discard the remaining bytes from the current packet */
+	if (buf_len < sshbuf_len(iqueue)) {
+		error("iqueue grew unexpectedly");
+		sftp_server_cleanup_exit(255);
+	}
+	consumed = buf_len - sshbuf_len(iqueue);
+	if (msg_len < consumed) {
+		error("msg_len %u < consumed %u", msg_len, consumed);
+		sftp_server_cleanup_exit(255);
+	}
+	if (msg_len > consumed &&
+	    (r = sshbuf_consume(iqueue, msg_len - consumed)) != 0)
+		fatal_fr(r, "consume");
+}
+
+/* Cleanup handler that logs active handles upon normal exit */
+void
+sftp_server_cleanup_exit(int i)
+{
+	if (pw != NULL && client_addr != NULL) {
+		handle_log_exit();
+		logit("session closed for local user %s from [%s]",
+		    pw->pw_name, client_addr);
+	}
+	_exit(i);
+}
+
+static void
+sftp_server_usage(void)
+{
+	extern char *__progname;
+
+	fprintf(stderr,
+	    "usage: %s [-ehR] [-d start_directory] [-f log_facility] "
+	    "[-l log_level]\n\t[-P denied_requests] "
+	    "[-p allowed_requests] [-u umask]\n"
+	    "       %s -Q protocol_feature\n",
+	    __progname, __progname);
+	exit(1);
+}
+
+int
+sftp_server_main(int argc, char **argv, struct passwd *user_pw)
+{
+	int i, r, in, out, ch, skipargs = 0, log_stderr = 0;
+	ssize_t len, olen;
+	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
+	char *cp, *homedir = NULL, uidstr[32], buf[4*4096];
+	long mask;
+
+	extern char *optarg;
+	extern char *__progname;
+
+	__progname = ssh_get_progname(argv[0]);
+	log_init(__progname, log_level, log_facility, log_stderr);
+
+	pw = pwcopy(user_pw);
+
+	while (!skipargs && (ch = getopt(argc, argv,
+	    "d:f:l:P:p:Q:u:cehR")) != -1) {
+		switch (ch) {
+		case 'Q':
+			if (strcasecmp(optarg, "requests") != 0) {
+				fprintf(stderr, "Invalid query type\n");
+				exit(1);
+			}
+			for (i = 0; handlers[i].handler != NULL; i++)
+				printf("%s\n", handlers[i].name);
+			for (i = 0; extended_handlers[i].handler != NULL; i++)
+				printf("%s\n", extended_handlers[i].name);
+			exit(0);
+			break;
+		case 'R':
+			readonly = 1;
+			break;
+		case 'c':
+			/*
+			 * Ignore all arguments if we are invoked as a
+			 * shell using "sftp-server -c command"
+			 */
+			skipargs = 1;
+			break;
+		case 'e':
+			log_stderr = 1;
+			break;
+		case 'l':
+			log_level = log_level_number(optarg);
+			if (log_level == SYSLOG_LEVEL_NOT_SET)
+				error("Invalid log level \"%s\"", optarg);
+			break;
+		case 'f':
+			log_facility = log_facility_number(optarg);
+			if (log_facility == SYSLOG_FACILITY_NOT_SET)
+				error("Invalid log facility \"%s\"", optarg);
+			break;
+		case 'd':
+			cp = tilde_expand_filename(optarg, user_pw->pw_uid);
+			snprintf(uidstr, sizeof(uidstr), "%llu",
+			    (unsigned long long)pw->pw_uid);
+			homedir = percent_expand(cp, "d", user_pw->pw_dir,
+			    "u", user_pw->pw_name, "U", uidstr, (char *)NULL);
+			free(cp);
+			break;
+		case 'p':
+			if (request_allowlist != NULL)
+				fatal("Permitted requests already set");
+			request_allowlist = xstrdup(optarg);
+			break;
+		case 'P':
+			if (request_denylist != NULL)
+				fatal("Refused requests already set");
+			request_denylist = xstrdup(optarg);
+			break;
+		case 'u':
+			errno = 0;
+			mask = strtol(optarg, &cp, 8);
+			if (mask < 0 || mask > 0777 || *cp != '\0' ||
+			    cp == optarg || (mask == 0 && errno != 0))
+				fatal("Invalid umask \"%s\"", optarg);
+			(void)umask((mode_t)mask);
+			break;
+		case 'h':
+		default:
+			sftp_server_usage();
+		}
+	}
+
+	log_init(__progname, log_level, log_facility, log_stderr);
+
+	/*
+	 * On platforms where we can, avoid making /proc/self/{mem,maps}
+	 * available to the user so that sftp access doesn't automatically
+	 * imply arbitrary code execution access that will break
+	 * restricted configurations.
+	 */
+	platform_disable_tracing(1);	/* strict */
+
+	/* Drop any fine-grained privileges we don't need */
+	platform_pledge_sftp_server();
+
+	if ((cp = getenv("SSH_CONNECTION")) != NULL) {
+		client_addr = xstrdup(cp);
+		if ((cp = strchr(client_addr, ' ')) == NULL) {
+			error("Malformed SSH_CONNECTION variable: \"%s\"",
+			    getenv("SSH_CONNECTION"));
+			sftp_server_cleanup_exit(255);
+		}
+		*cp = '\0';
+	} else
+		client_addr = xstrdup("UNKNOWN");
+
+	logit("session opened for local user %s from [%s]",
+	    pw->pw_name, client_addr);
+
+	in = STDIN_FILENO;
+	out = STDOUT_FILENO;
+
+#ifdef HAVE_CYGWIN
+	setmode(in, O_BINARY);
+	setmode(out, O_BINARY);
+#endif
+
+	if ((iqueue = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	if ((oqueue = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+
+	if (homedir != NULL) {
+		if (chdir(homedir) != 0) {
+			error("chdir to \"%s\" failed: %s", homedir,
+			    strerror(errno));
+		}
+	}
+
+	for (;;) {
+		struct pollfd pfd[2];
+
+		memset(pfd, 0, sizeof pfd);
+		pfd[0].fd = pfd[1].fd = -1;
+
+		/*
+		 * Ensure that we can read a full buffer and handle
+		 * the worst-case length packet it can generate,
+		 * otherwise apply backpressure by stopping reads.
+		 */
+		if ((r = sshbuf_check_reserve(iqueue, sizeof(buf))) == 0 &&
+		    (r = sshbuf_check_reserve(oqueue,
+		    SFTP_MAX_MSG_LENGTH)) == 0) {
+			pfd[0].fd = in;
+			pfd[0].events = POLLIN;
+		}
+		else if (r != SSH_ERR_NO_BUFFER_SPACE)
+			fatal_fr(r, "reserve");
+
+		olen = sshbuf_len(oqueue);
+		if (olen > 0) {
+			pfd[1].fd = out;
+			pfd[1].events = POLLOUT;
+		}
+
+		if (poll(pfd, 2, -1) == -1) {
+			if (errno == EINTR)
+				continue;
+			error("poll: %s", strerror(errno));
+			sftp_server_cleanup_exit(2);
+		}
+
+		/* copy stdin to iqueue */
+		if (pfd[0].revents & (POLLIN|POLLHUP)) {
+			len = read(in, buf, sizeof buf);
+			if (len == 0) {
+				debug("read eof");
+				sftp_server_cleanup_exit(0);
+			} else if (len == -1) {
+				if (errno != EAGAIN && errno != EINTR) {
+					error("read: %s", strerror(errno));
+					sftp_server_cleanup_exit(1);
+				}
+			} else if ((r = sshbuf_put(iqueue, buf, len)) != 0)
+				fatal_fr(r, "sshbuf_put");
+		}
+		/* send oqueue to stdout */
+		if (pfd[1].revents & (POLLOUT|POLLHUP)) {
+			len = write(out, sshbuf_ptr(oqueue), olen);
+			if (len == 0 || (len == -1 && errno == EPIPE)) {
+				debug("write eof");
+				sftp_server_cleanup_exit(0);
+			} else if (len == -1) {
+				sftp_server_cleanup_exit(1);
+				if (errno != EAGAIN && errno != EINTR) {
+					error("write: %s", strerror(errno));
+					sftp_server_cleanup_exit(1);
+				}
+			} else if ((r = sshbuf_consume(oqueue, len)) != 0)
+				fatal_fr(r, "consume");
+		}
+
+		/*
+		 * Process requests from client if we can fit the results
+		 * into the output buffer, otherwise stop processing input
+		 * and let the output queue drain.
+		 */
+		r = sshbuf_check_reserve(oqueue, SFTP_MAX_MSG_LENGTH);
+		if (r == 0)
+			process();
+		else if (r != SSH_ERR_NO_BUFFER_SPACE)
+			fatal_fr(r, "reserve");
+	}
+}