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authordjm@openbsd.org <djm@openbsd.org>2021-08-09 23:47:44 +0000
committerDamien Miller <djm@mindrot.org>2021-08-10 12:47:46 +1000
commit2ab864010e0a93c5dd95116fb5ceaf430e2fc23c (patch)
tree2851434ba4912fd244aa2e327580b606e86b159e
parent41b019ac067f1d1f7d99914d0ffee4d2a547c3d8 (diff)
upstream: SFTP protocol extension to allow the server to expand
~-prefixed paths, in particular ~user ones. Allows scp in sftp mode to accept these paths, like scp in rcp mode does. prompted by and much discussion deraadt@ ok markus@ OpenBSD-Commit-ID: 7d794def9e4de348e1e777f6030fc9bafdfff392
-rw-r--r--PROTOCOL21
-rw-r--r--misc.c49
-rw-r--r--misc.h3
-rw-r--r--scp.c17
-rw-r--r--sftp-client.c59
-rw-r--r--sftp-client.h10
-rw-r--r--sftp-server.c63
7 files changed, 187 insertions, 35 deletions
diff --git a/PROTOCOL b/PROTOCOL
index 0b2ea60a..3141cda6 100644
--- a/PROTOCOL
+++ b/PROTOCOL
@@ -525,6 +525,25 @@ limits.
This extension is advertised in the SSH_FXP_VERSION hello with version
"1".
+3.9. sftp: Extension request "expand-path@openssh.com"
+
+This request supports canonicalisation of relative paths and
+those that need tilde-expansion, i.e. "~", "~/..." and "~user/..."
+These paths are expanded using shell-like rules and the resultant
+path is canonicalised similarly to SSH2_FXP_REALPATH.
+
+It is implemented as a SSH_FXP_EXTENDED request with the following
+format:
+
+ uint32 id
+ string "expand-path@openssh.com"
+ string path
+
+Its reply is the same format as that of SSH2_FXP_REALPATH.
+
+This extension is advertised in the SSH_FXP_VERSION hello with version
+"1".
+
4. Miscellaneous changes
4.1 Public key format
@@ -556,4 +575,4 @@ OpenSSH's connection multiplexing uses messages as described in
PROTOCOL.mux over a Unix domain socket for communications between a
master instance and later clients.
-$OpenBSD: PROTOCOL,v 1.41 2021/02/18 02:49:35 djm Exp $
+$OpenBSD: PROTOCOL,v 1.42 2021/08/09 23:47:44 djm Exp $
diff --git a/misc.c b/misc.c
index adfe9033..b8d1040d 100644
--- a/misc.c
+++ b/misc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.168 2021/07/12 06:22:57 dtucker Exp $ */
+/* $OpenBSD: misc.c,v 1.169 2021/08/09 23:47:44 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2005-2020 Damien Miller. All rights reserved.
@@ -1115,29 +1115,37 @@ freeargs(arglist *args)
* Expands tildes in the file name. Returns data allocated by xmalloc.
* Warning: this calls getpw*.
*/
-char *
-tilde_expand_filename(const char *filename, uid_t uid)
+int
+tilde_expand(const char *filename, uid_t uid, char **retp)
{
const char *path, *sep;
char user[128], *ret;
struct passwd *pw;
u_int len, slash;
- if (*filename != '~')
- return (xstrdup(filename));
+ if (*filename != '~') {
+ *retp = xstrdup(filename);
+ return 0;
+ }
filename++;
path = strchr(filename, '/');
if (path != NULL && path > filename) { /* ~user/path */
slash = path - filename;
- if (slash > sizeof(user) - 1)
- fatal("tilde_expand_filename: ~username too long");
+ if (slash > sizeof(user) - 1) {
+ error_f("~username too long");
+ return -1;
+ }
memcpy(user, filename, slash);
user[slash] = '\0';
- if ((pw = getpwnam(user)) == NULL)
- fatal("tilde_expand_filename: No such user %s", user);
- } else if ((pw = getpwuid(uid)) == NULL) /* ~/path */
- fatal("tilde_expand_filename: No such uid %ld", (long)uid);
+ if ((pw = getpwnam(user)) == NULL) {
+ error_f("No such user %s", user);
+ return -1;
+ }
+ } else if ((pw = getpwuid(uid)) == NULL) { /* ~/path */
+ error_f("No such uid %ld", (long)uid);
+ return -1;
+ }
/* Make sure directory has a trailing '/' */
len = strlen(pw->pw_dir);
@@ -1150,10 +1158,23 @@ tilde_expand_filename(const char *filename, uid_t uid)
if (path != NULL)
filename = path + 1;
- if (xasprintf(&ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX)
- fatal("tilde_expand_filename: Path too long");
+ if (xasprintf(&ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX) {
+ error_f("Path too long");
+ return -1;
+ }
+
+ *retp = ret;
+ return 0;
+}
- return (ret);
+char *
+tilde_expand_filename(const char *filename, uid_t uid)
+{
+ char *ret;
+
+ if (tilde_expand(filename, uid, &ret) != 0)
+ cleanup_exit(255);
+ return ret;
}
/*
diff --git a/misc.h b/misc.h
index dd899a32..2e2dca54 100644
--- a/misc.h
+++ b/misc.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.h,v 1.97 2021/06/08 06:54:40 djm Exp $ */
+/* $OpenBSD: misc.h,v 1.98 2021/08/09 23:47:44 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -71,6 +71,7 @@ int parse_user_host_port(const char *, char **, char **, int *);
int parse_uri(const char *, const char *, char **, char **, int *, char **);
int convtime(const char *);
const char *fmt_timeframe(time_t t);
+int tilde_expand(const char *, uid_t, char **);
char *tilde_expand_filename(const char *, uid_t);
char *dollar_expand(int *, const char *string, ...);
diff --git a/scp.c b/scp.c
index fe3ac701..a0377c6c 100644
--- a/scp.c
+++ b/scp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: scp.c,v 1.226 2021/08/09 23:44:32 djm Exp $ */
+/* $OpenBSD: scp.c,v 1.227 2021/08/09 23:47:44 djm Exp $ */
/*
* scp - secure remote copy. This is basically patched BSD rcp which
* uses ssh to do the data transfer (instead of using rcmd).
@@ -1255,10 +1255,14 @@ tolocal(int argc, char **argv, enum scp_mode_e mode, char *sftp_direct)
/* Canonicalise a remote path, handling ~ by assuming cwd is the homedir */
static char *
-absolute_remote_path(const char *path, const char *remote_path)
+absolute_remote_path(struct sftp_conn *conn, const char *path,
+ const char *remote_path)
{
char *ret;
+ if (can_expand_path(conn))
+ return do_expand_path(conn, path);
+
/* Handle ~ prefixed paths */
if (*path != '~')
ret = xstrdup(path);
@@ -1296,7 +1300,7 @@ source_sftp(int argc, char *src, char *targ,
* No need to glob here - the local shell already took care of
* the expansions
*/
- if ((target = absolute_remote_path(targ, *remote_path)) == NULL)
+ if ((target = absolute_remote_path(conn, targ, *remote_path)) == NULL)
cleanup_exit(255);
target_is_dir = remote_is_dir(conn, target);
if (targetshouldbedirectory && !target_is_dir) {
@@ -1508,7 +1512,7 @@ sink_sftp(int argc, char *dst, const char *src, struct sftp_conn *conn)
goto out;
}
- if ((abs_src = absolute_remote_path(src, remote_path)) == NULL) {
+ if ((abs_src = absolute_remote_path(conn, src, remote_path)) == NULL) {
err = -1;
goto out;
}
@@ -1920,8 +1924,9 @@ throughlocal_sftp(struct sftp_conn *from, struct sftp_conn *to,
if ((filename = basename(src)) == NULL)
fatal("basename %s: %s", src, strerror(errno));
- if ((abs_src = absolute_remote_path(src, from_remote_path)) == NULL ||
- (target = absolute_remote_path(targ, *to_remote_path)) == NULL)
+ if ((abs_src = absolute_remote_path(from, src,
+ from_remote_path)) == NULL ||
+ (target = absolute_remote_path(to, targ, *to_remote_path)) == NULL)
cleanup_exit(255);
free(from_remote_path);
memset(&g, 0, sizeof(g));
diff --git a/sftp-client.c b/sftp-client.c
index ce31c35a..5bfff90d 100644
--- a/sftp-client.c
+++ b/sftp-client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-client.c,v 1.153 2021/08/09 07:16:09 djm Exp $ */
+/* $OpenBSD: sftp-client.c,v 1.154 2021/08/09 23:47:44 djm Exp $ */
/*
* Copyright (c) 2001-2004 Damien Miller <djm@openbsd.org>
*
@@ -102,6 +102,7 @@ struct sftp_conn {
#define SFTP_EXT_FSYNC 0x00000010
#define SFTP_EXT_LSETSTAT 0x00000020
#define SFTP_EXT_LIMITS 0x00000040
+#define SFTP_EXT_PATH_EXPAND 0x00000080
u_int exts;
u_int64_t limit_kbps;
struct bwlimit bwlimit_in, bwlimit_out;
@@ -529,6 +530,10 @@ do_init(int fd_in, int fd_out, u_int transfer_buflen, u_int num_requests,
strcmp((char *)value, "1") == 0) {
ret->exts |= SFTP_EXT_LIMITS;
known = 1;
+ } else if (strcmp(name, "expand-path@openssh.com") == 0 &&
+ strcmp((char *)value, "1") == 0) {
+ ret->exts |= SFTP_EXT_PATH_EXPAND;
+ known = 1;
}
if (known) {
debug2("Server supports extension \"%s\" revision %s",
@@ -964,8 +969,9 @@ do_fsetstat(struct sftp_conn *conn, const u_char *handle, u_int handle_len,
return status == SSH2_FX_OK ? 0 : -1;
}
-char *
-do_realpath(struct sftp_conn *conn, const char *path)
+/* Implements both the realpath and expand-path operations */
+static char *
+do_realpath_expand(struct sftp_conn *conn, const char *path, int expand)
{
struct sshbuf *msg;
u_int expected_id, count, id;
@@ -973,14 +979,26 @@ do_realpath(struct sftp_conn *conn, const char *path)
Attrib a;
u_char type;
int r;
+ const char *what = "SSH2_FXP_REALPATH";
- expected_id = id = conn->msg_id++;
- send_string_request(conn, id, SSH2_FXP_REALPATH, path,
- strlen(path));
-
+ if (expand)
+ what = "expand-path@openssh.com";
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
+ expected_id = id = conn->msg_id++;
+ if (expand) {
+ if ((r = sshbuf_put_u8(msg, SSH2_FXP_EXTENDED)) != 0 ||
+ (r = sshbuf_put_u32(msg, id)) != 0 ||
+ (r = sshbuf_put_cstring(msg,
+ "expand-path@openssh.com")) != 0 ||
+ (r = sshbuf_put_cstring(msg, path)) != 0)
+ fatal_fr(r, "compose %s", what);
+ send_msg(conn, msg);
+ } else {
+ send_string_request(conn, id, SSH2_FXP_REALPATH,
+ path, strlen(path));
+ }
get_msg(conn, msg);
if ((r = sshbuf_get_u8(msg, &type)) != 0 ||
(r = sshbuf_get_u32(msg, &id)) != 0)
@@ -1004,15 +1022,14 @@ do_realpath(struct sftp_conn *conn, const char *path)
if ((r = sshbuf_get_u32(msg, &count)) != 0)
fatal_fr(r, "parse count");
if (count != 1)
- fatal("Got multiple names (%d) from SSH_FXP_REALPATH", count);
+ fatal("Got multiple names (%d) from %s", count, what);
if ((r = sshbuf_get_cstring(msg, &filename, NULL)) != 0 ||
(r = sshbuf_get_cstring(msg, &longname, NULL)) != 0 ||
(r = decode_attrib(msg, &a)) != 0)
fatal_fr(r, "parse filename/attrib");
- debug3("SSH_FXP_REALPATH %s -> %s size %lu", path, filename,
- (unsigned long)a.size);
+ debug3("%s %s -> %s", what, path, filename);
free(longname);
@@ -1021,6 +1038,28 @@ do_realpath(struct sftp_conn *conn, const char *path)
return(filename);
}
+char *
+do_realpath(struct sftp_conn *conn, const char *path)
+{
+ return do_realpath_expand(conn, path, 0);
+}
+
+int
+can_expand_path(struct sftp_conn *conn)
+{
+ return (conn->exts & SFTP_EXT_PATH_EXPAND) != 0;
+}
+
+char *
+do_expand_path(struct sftp_conn *conn, const char *path)
+{
+ if (!can_expand_path(conn)) {
+ debug3_f("no server support, fallback to realpath");
+ return do_realpath_expand(conn, path, 0);
+ }
+ return do_realpath_expand(conn, path, 1);
+}
+
int
do_rename(struct sftp_conn *conn, const char *oldpath, const char *newpath,
int force_legacy)
diff --git a/sftp-client.h b/sftp-client.h
index 00707f7c..7d0bd12a 100644
--- a/sftp-client.h
+++ b/sftp-client.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-client.h,v 1.33 2021/08/07 00:12:09 djm Exp $ */
+/* $OpenBSD: sftp-client.h,v 1.34 2021/08/09 23:47:44 djm Exp $ */
/*
* Copyright (c) 2001-2004 Damien Miller <djm@openbsd.org>
@@ -113,11 +113,17 @@ int do_lsetstat(struct sftp_conn *conn, const char *path, Attrib *a);
/* Canonicalise 'path' - caller must free result */
char *do_realpath(struct sftp_conn *, const char *);
+/* Canonicalisation with tilde expansion (requires server extension) */
+char *do_expand_path(struct sftp_conn *, const char *);
+
+/* Returns non-zero if server can tilde-expand paths */
+int can_expand_path(struct sftp_conn *);
+
/* Get statistics for filesystem hosting file at "path" */
int do_statvfs(struct sftp_conn *, const char *, struct sftp_statvfs *, int);
/* Rename 'oldpath' to 'newpath' */
-int do_rename(struct sftp_conn *, const char *, const char *, int force_legacy);
+int do_rename(struct sftp_conn *, const char *, const char *, int);
/* Link 'oldpath' to 'newpath' */
int do_hardlink(struct sftp_conn *, const char *, const char *);
diff --git a/sftp-server.c b/sftp-server.c
index c89c1f42..18d19491 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-server.c,v 1.128 2021/06/06 03:15:39 djm Exp $ */
+/* $OpenBSD: sftp-server.c,v 1.129 2021/08/09 23:47:44 djm Exp $ */
/*
* Copyright (c) 2000-2004 Markus Friedl. All rights reserved.
*
@@ -115,6 +115,7 @@ 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(u_int32_t id);
struct sftp_handler {
@@ -158,6 +159,8 @@ static const struct sftp_handler extended_handlers[] = {
{ "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 },
{ NULL, NULL, 0, NULL, 0 }
};
@@ -706,6 +709,7 @@ process_init(void)
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");
send_msg(msg);
sshbuf_free(msg);
@@ -1520,6 +1524,63 @@ process_extended_limits(u_int32_t id)
}
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);
+ } else {
+ /* ~user expansions */
+ if (tilde_expand(path, pw->pw_uid, &npath) != 0) {
+ send_status(id, errno_to_portable(EINVAL));
+ 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(u_int32_t id)
{
char *request;