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scp: switch to using the SFTP protocol by default

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From upstream release notes https://www.openssh.com/txt/release-9.0

This release switches scp(1) from using the legacy scp/rcp protocol
to using the SFTP protocol by default.

Legacy scp/rcp performs wildcard expansion of remote filenames (e.g.
"scp host:* .") through the remote shell. This has the side effect of
requiring double quoting of shell meta-characters in file names
included on scp(1) command-lines, otherwise they could be interpreted
as shell commands on the remote side.

This creates one area of potential incompatibility: scp(1) when using
the SFTP protocol no longer requires this finicky and brittle quoting,
and attempts to use it may cause transfers to fail. We consider the
removal of the need for double-quoting shell characters in file names
to be a benefit and do not intend to introduce bug-compatibility for
legacy scp/rcp in scp(1) when using the SFTP protocol.

Another area of potential incompatibility relates to the use of remote
paths relative to other user's home directories, for example -
"scp host:~user/file /tmp". The SFTP protocol has no native way to
expand a ~user path. However, sftp-server(8) in OpenSSH 8.7 and later
support a protocol extension "expand-path@openssh.com" to support
this.

In case of incompatibility, the scp(1) client may be instructed to use
the legacy scp/rcp using the -O flag.

Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Ed Maste 2022-04-13 20:50:17 -04:00
parent 87c1498d1a
commit fb5aabcb99
2 changed files with 15 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

24
crypto/openssh/scp.1
View file

@ -8,9 +8,9 @@
.\"
.\" Created: Sun May 7 00:14:37 1995 ylo
.\"
.\" $OpenBSD: scp.1,v 1.107 2022/02/10 04:12:38 djm Exp $
.\" $OpenBSD: scp.1,v 1.108 2022/02/23 21:21:16 djm Exp $
.\"
.Dd $Mdocdate: February 10 2022 $
.Dd $Mdocdate: February 23 2022 $
.Dt SCP 1
.Os
.Sh NAME
@ -76,7 +76,9 @@ The options are as follows:
Copies between two remote hosts are transferred through the local host.
Without this option the data is copied directly between the two remote
hosts.
Note that, when using the original SCP protocol (the default), this option
Note that, when using the legacy SCP protocol (via the
.Fl O
flag), this option
selects batch mode for the second host as
.Nm
cannot ask for passwords or passphrases for both hosts.
@ -109,7 +111,7 @@ This option is directly passed to
.Xr ssh 1 .
.It Fl D Ar sftp_server_path
When using the SFTP protocol support via
.Fl s ,
.Fl M ,
connect directly to a local SFTP server program rather than a
remote one via
.Xr ssh 1 .
@ -141,13 +143,12 @@ This option is directly passed to
.It Fl l Ar limit
Limits the used bandwidth, specified in Kbit/s.
.It Fl O
Use the original SCP protocol for file transfers instead of the SFTP protocol.
Use the legacy SCP protocol for file transfers instead of the SFTP protocol.
Forcing the use of the SCP protocol may be necessary for servers that do
not implement SFTP, for backwards-compatibility for particular filename
wildcard patterns and for expanding paths with a
.Sq ~
prefix for older SFTP servers.
This mode is the default.
.It Fl o Ar ssh_option
Can be used to pass options to
.Nm ssh
@ -257,8 +258,6 @@ to use for the encrypted connection.
The program must understand
.Xr ssh 1
options.
.It Fl s
Use the SFTP protocol for transfers rather than the original scp protocol.
.It Fl T
Disable strict filename checking.
By default when copying files from a remote host to a local directory
@ -295,12 +294,17 @@ debugging connection, authentication, and configuration problems.
is based on the rcp program in
.Bx
source code from the Regents of the University of California.
.Pp
Since OpenSSH 9.0,
.Nm
has use the SFTP protocol for transfers by default.
.Sh AUTHORS
.An Timo Rinne Aq Mt tri@iki.fi
.An Tatu Ylonen Aq Mt ylo@cs.hut.fi
.Sh CAVEATS
The original SCP protocol (used by default) requires execution of the
remote user's shell to perform
The legacy SCP protocol (selected by the
.Fl O
flag) requires execution of the remote user's shell to perform
.Xr glob 3
pattern matching.
This requires careful quoting of any characters that have special meaning to

2
crypto/openssh/scp.c
View file

@ -449,7 +449,7 @@ main(int argc, char **argv)
const char *errstr;
extern char *optarg;
extern int optind;
enum scp_mode_e mode = MODE_SCP;
enum scp_mode_e mode = MODE_SFTP;
char *sftp_direct = NULL;
/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */