freebsd-dev/crypto/openssh/scp.1
Ed Maste fb5aabcb99 scp: switch to using the SFTP protocol by default
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
2022-04-15 10:47:28 -04:00

312 lines
7.4 KiB
Groff

.\"
.\" scp.1
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\"
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\" All rights reserved
.\"
.\" Created: Sun May 7 00:14:37 1995 ylo
.\"
.\" $OpenBSD: scp.1,v 1.108 2022/02/23 21:21:16 djm Exp $
.\"
.Dd $Mdocdate: February 23 2022 $
.Dt SCP 1
.Os
.Sh NAME
.Nm scp
.Nd OpenSSH secure file copy
.Sh SYNOPSIS
.Nm scp
.Op Fl 346ABCOpqRrsTv
.Op Fl c Ar cipher
.Op Fl D Ar sftp_server_path
.Op Fl F Ar ssh_config
.Op Fl i Ar identity_file
.Op Fl J Ar destination
.Op Fl l Ar limit
.Op Fl o Ar ssh_option
.Op Fl P Ar port
.Op Fl S Ar program
.Ar source ... target
.Sh DESCRIPTION
.Nm
copies files between hosts on a network.
.Pp
It uses
.Xr ssh 1
for data transfer, and uses the same authentication and provides the
same security as a login session.
.Pp
.Nm
will ask for passwords or passphrases if they are needed for
authentication.
.Pp
The
.Ar source
and
.Ar target
may be specified as a local pathname, a remote host with optional path
in the form
.Sm off
.Oo user @ Oc host : Op path ,
.Sm on
or a URI in the form
.Sm off
.No scp:// Oo user @ Oc host Oo : port Oc Op / path .
.Sm on
Local file names can be made explicit using absolute or relative pathnames
to avoid
.Nm
treating file names containing
.Sq :\&
as host specifiers.
.Pp
When copying between two remote hosts, if the URI format is used, a
.Ar port
cannot be specified on the
.Ar target
if the
.Fl R
option is used.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 3
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 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.
This mode is the default.
.It Fl 4
Forces
.Nm
to use IPv4 addresses only.
.It Fl 6
Forces
.Nm
to use IPv6 addresses only.
.It Fl A
Allows forwarding of
.Xr ssh-agent 1
to the remote system.
The default is not to forward an authentication agent.
.It Fl B
Selects batch mode (prevents asking for passwords or passphrases).
.It Fl C
Compression enable.
Passes the
.Fl C
flag to
.Xr ssh 1
to enable compression.
.It Fl c Ar cipher
Selects the cipher to use for encrypting the data transfer.
This option is directly passed to
.Xr ssh 1 .
.It Fl D Ar sftp_server_path
When using the SFTP protocol support via
.Fl M ,
connect directly to a local SFTP server program rather than a
remote one via
.Xr ssh 1 .
This option may be useful in debugging the client and server.
.It Fl F Ar ssh_config
Specifies an alternative
per-user configuration file for
.Nm ssh .
This option is directly passed to
.Xr ssh 1 .
.It Fl i Ar identity_file
Selects the file from which the identity (private key) for public key
authentication is read.
This option is directly passed to
.Xr ssh 1 .
.It Fl J Ar destination
Connect to the target host by first making an
.Nm
connection to the jump host described by
.Ar destination
and then establishing a TCP forwarding to the ultimate destination from
there.
Multiple jump hops may be specified separated by comma characters.
This is a shortcut to specify a
.Cm ProxyJump
configuration directive.
This option is directly passed to
.Xr ssh 1 .
.It Fl l Ar limit
Limits the used bandwidth, specified in Kbit/s.
.It Fl O
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.
.It Fl o Ar ssh_option
Can be used to pass options to
.Nm ssh
in the format used in
.Xr ssh_config 5 .
This is useful for specifying options
for which there is no separate
.Nm scp
command-line flag.
For full details of the options listed below, and their possible values, see
.Xr ssh_config 5 .
.Pp
.Bl -tag -width Ds -offset indent -compact
.It AddressFamily
.It BatchMode
.It BindAddress
.It BindInterface
.It CanonicalDomains
.It CanonicalizeFallbackLocal
.It CanonicalizeHostname
.It CanonicalizeMaxDots
.It CanonicalizePermittedCNAMEs
.It CASignatureAlgorithms
.It CertificateFile
.It CheckHostIP
.It Ciphers
.It Compression
.It ConnectionAttempts
.It ConnectTimeout
.It ControlMaster
.It ControlPath
.It ControlPersist
.It GlobalKnownHostsFile
.It GSSAPIAuthentication
.It GSSAPIDelegateCredentials
.It HashKnownHosts
.It Host
.It HostbasedAcceptedAlgorithms
.It HostbasedAuthentication
.It HostKeyAlgorithms
.It HostKeyAlias
.It Hostname
.It IdentitiesOnly
.It IdentityAgent
.It IdentityFile
.It IPQoS
.It KbdInteractiveAuthentication
.It KbdInteractiveDevices
.It KexAlgorithms
.It KnownHostsCommand
.It LogLevel
.It MACs
.It NoHostAuthenticationForLocalhost
.It NumberOfPasswordPrompts
.It PasswordAuthentication
.It PKCS11Provider
.It Port
.It PreferredAuthentications
.It ProxyCommand
.It ProxyJump
.It PubkeyAcceptedAlgorithms
.It PubkeyAuthentication
.It RekeyLimit
.It SendEnv
.It ServerAliveInterval
.It ServerAliveCountMax
.It SetEnv
.It StrictHostKeyChecking
.It TCPKeepAlive
.It UpdateHostKeys
.It User
.It UserKnownHostsFile
.It VerifyHostKeyDNS
.El
.It Fl P Ar port
Specifies the port to connect to on the remote host.
Note that this option is written with a capital
.Sq P ,
because
.Fl p
is already reserved for preserving the times and mode bits of the file.
.It Fl p
Preserves modification times, access times, and file mode bits from the
source file.
.It Fl q
Quiet mode: disables the progress meter as well as warning and diagnostic
messages from
.Xr ssh 1 .
.It Fl R
Copies between two remote hosts are performed by connecting to the origin
host and executing
.Nm
there.
This requires that
.Nm
running on the origin host can authenticate to the destination host without
requiring a password.
.It Fl r
Recursively copy entire directories.
Note that
.Nm
follows symbolic links encountered in the tree traversal.
.It Fl S Ar program
Name of
.Ar program
to use for the encrypted connection.
The program must understand
.Xr ssh 1
options.
.It Fl T
Disable strict filename checking.
By default when copying files from a remote host to a local directory
.Nm
checks that the received filenames match those requested on the command-line
to prevent the remote end from sending unexpected or unwanted files.
Because of differences in how various operating systems and shells interpret
filename wildcards, these checks may cause wanted files to be rejected.
This option disables these checks at the expense of fully trusting that
the server will not send unexpected filenames.
.It Fl v
Verbose mode.
Causes
.Nm
and
.Xr ssh 1
to print debugging messages about their progress.
This is helpful in
debugging connection, authentication, and configuration problems.
.El
.Sh EXIT STATUS
.Ex -std scp
.Sh SEE ALSO
.Xr sftp 1 ,
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-agent 1 ,
.Xr ssh-keygen 1 ,
.Xr ssh_config 5 ,
.Xr sftp-server 8 ,
.Xr sshd 8
.Sh HISTORY
.Nm
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 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
the remote shell, such as quote characters.