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upstream: do not advertise protocol extensions that have been 

disallowed by the command-line options (e.g. -p/-P/-R); ok dtucker@

OpenBSD-Commit-ID: 3a8a76b3f5131741aca4b41bfab8d101c9926205
This commit is contained in:
djm@openbsd.org 2021-03-31 21:58:07 +00:00 committed by Damien Miller
parent 71241fc05d
commit 6653c61202
1 changed files with 53 additions and 33 deletions

86
sftp-server.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: sftp-server.c,v 1.124 2021/03/19 02:18:28 djm Exp $ */
/* $OpenBSD: sftp-server.c,v 1.125 2021/03/31 21:58:07 djm Exp $ */
/*
* Copyright (c) 2000-2004 Markus Friedl. All rights reserved.
*
@ -161,6 +161,18 @@ static const struct sftp_handler extended_handlers[] = {
{ 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)
{
@ -647,6 +659,28 @@ send_statvfs(u_int32_t id, struct statvfs *st)
sshbuf_free(msg);
}
/*
* Prepare SSH2_FXP_VERSION extension advertisement for a single extension.
* The extension is checked for permission prior to advertisment.
*/
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
@ -661,29 +695,18 @@ process_init(void)
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 ||
/* POSIX rename extension */
(r = sshbuf_put_cstring(msg, "posix-rename@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "1")) != 0 || /* version */
/* statvfs extension */
(r = sshbuf_put_cstring(msg, "statvfs@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "2")) != 0 || /* version */
/* fstatvfs extension */
(r = sshbuf_put_cstring(msg, "fstatvfs@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "2")) != 0 || /* version */
/* hardlink extension */
(r = sshbuf_put_cstring(msg, "hardlink@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "1")) != 0 || /* version */
/* fsync extension */
(r = sshbuf_put_cstring(msg, "fsync@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "1")) != 0 || /* version */
/* lsetstat extension */
(r = sshbuf_put_cstring(msg, "lsetstat@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "1")) != 0 || /* version */
/* limits extension */
(r = sshbuf_put_cstring(msg, "limits@openssh.com")) != 0 ||
(r = sshbuf_put_cstring(msg, "1")) != 0) /* version */
(r = sshbuf_put_u32(msg, SSH2_FILEXFER_VERSION)) != 0)
fatal_fr(r, "compose");
/* extension advertisments */
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");
send_msg(msg);
sshbuf_free(msg);
}
@ -1497,21 +1520,18 @@ process_extended(u_int32_t id)
{
char *request;
int i, r;
const struct sftp_handler *exthand;
if ((r = sshbuf_get_cstring(iqueue, &request, NULL)) != 0)
fatal_fr(r, "parse");
for (i = 0; extended_handlers[i].handler != NULL; i++) {
if (strcmp(request, extended_handlers[i].ext_name) == 0) {
if (!request_permitted(&extended_handlers[i]))
send_status(id, SSH2_FX_PERMISSION_DENIED);
else
extended_handlers[i].handler(id);
break;
}
}
if (extended_handlers[i].handler == NULL) {
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);
}