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Disabling SCP protocol as much as possible

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Resolves: rhbz#2001002
This commit is contained in:
Dmitry Belyavskiy 2021-09-24 16:51:04 +02:00
parent f9e5ded9dd
commit f32839a5e4
3 changed files with 185 additions and 1 deletions
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46
openssh-8.7p1-scp-kill-switch.patch Normal file
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@ -0,0 +1,46 @@
diff -up openssh-8.7p1/pathnames.h.kill-scp openssh-8.7p1/pathnames.h
--- openssh-8.7p1/pathnames.h.kill-scp 2021-09-16 11:37:57.240171687 +0200
+++ openssh-8.7p1/pathnames.h 2021-09-16 11:42:29.183427917 +0200
@@ -42,6 +42,7 @@
#define _PATH_HOST_XMSS_KEY_FILE SSHDIR "/ssh_host_xmss_key"
#define _PATH_HOST_RSA_KEY_FILE SSHDIR "/ssh_host_rsa_key"
#define _PATH_DH_MODULI SSHDIR "/moduli"
+#define _PATH_SCP_KILL_SWITCH SSHDIR "/disable_scp"
#ifndef _PATH_SSH_PROGRAM
#define _PATH_SSH_PROGRAM "/usr/bin/ssh"
diff -up openssh-8.7p1/scp.1.kill-scp openssh-8.7p1/scp.1
--- openssh-8.7p1/scp.1.kill-scp 2021-09-16 12:09:02.646714578 +0200
+++ openssh-8.7p1/scp.1 2021-09-16 12:26:49.978628226 +0200
@@ -278,6 +278,13 @@ to print debugging messages about their
This is helpful in
debugging connection, authentication, and configuration problems.
.El
+.Pp
+Usage of SCP protocol can be blocked by creating a world-readable
+.Ar /etc/ssh/disable_scp
+file. If this file exists, when SCP protocol is in use (either remotely or
+via the
+.Fl O
+option), the program will exit.
.Sh EXIT STATUS
.Ex -std scp
.Sh SEE ALSO
diff -up openssh-8.7p1/scp.c.kill-scp openssh-8.7p1/scp.c
--- openssh-8.7p1/scp.c.kill-scp 2021-09-16 11:42:56.013650519 +0200
+++ openssh-8.7p1/scp.c 2021-09-16 11:53:03.249713836 +0200
@@ -596,6 +596,14 @@ main(int argc, char **argv)
if (iamremote)
mode = MODE_SCP;
+ if (mode == MODE_SCP) {
+ FILE *f = fopen(_PATH_SCP_KILL_SWITCH, "r");
+ if (f != NULL) {
+ fclose(f);
+ fatal("SCP protocol is forbidden via %s", _PATH_SCP_KILL_SWITCH);
+ }
+ }
+
if ((pwd = getpwuid(userid = getuid())) == NULL)
fatal("unknown user %u", (u_int) userid);

129
openssh-8.7p1-sftp-default-protocol.patch Normal file
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@ -0,0 +1,129 @@
diff --git a/scp.1 b/scp.1
index 68aac04b..a96e95ad 100644
--- a/scp.1
+++ b/scp.1
@@ -8,9 +8,9 @@
.\"
.\" Created: Sun May 7 00:14:37 1995 ylo
.\"
-.\" $OpenBSD: scp.1,v 1.100 2021/08/11 14:07:54 naddy Exp $
+.\" $OpenBSD: scp.1,v 1.101 2021/09/08 23:31:39 djm Exp $
.\"
-.Dd $Mdocdate: August 11 2021 $
+.Dd $Mdocdate: September 8 2021 $
.Dt SCP 1
.Os
.Sh NAME
@@ -18,7 +18,7 @@
.Nd OpenSSH secure file copy
.Sh SYNOPSIS
.Nm scp
-.Op Fl 346ABCOpqRrsTv
+.Op Fl 346ABCOpqRrTv
.Op Fl c Ar cipher
.Op Fl D Ar sftp_server_path
.Op Fl F Ar ssh_config
@@ -37,9 +37,6 @@ It uses
.Xr ssh 1
for data transfer, and uses the same authentication and provides the
same security as a login session.
-The scp protocol requires execution of the remote user's shell to perform
-.Xr glob 3
-pattern matching.
.Pp
.Nm
will ask for passwords or passphrases if they are needed for
@@ -79,7 +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 legacy 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.
@@ -146,9 +145,10 @@ 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 or for backwards-compatibility for particular filename
-wildcard patterns.
-This mode is the default.
+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
@@ -258,16 +258,6 @@ to use for the encrypted connection.
The program must understand
.Xr ssh 1
options.
-.It Fl s
-Use the SFTP protocol for file transfers instead of the legacy SCP protocol.
-Using SFTP avoids invoking a shell on the remote side and provides
-more predictable filename handling, as the SCP protocol
-relied on the remote shell for expanding
-.Xr glob 3
-wildcards.
-.Pp
-A near-future release of OpenSSH will make the SFTP protocol the default.
-This option will be deleted before the end of 2022.
.It Fl T
Disable strict filename checking.
By default when copying files from a remote host to a local directory
@@ -299,11 +289,23 @@ debugging connection, authentication, and configuration problems.
.Xr ssh_config 5 ,
.Xr sftp-server 8 ,
.Xr sshd 8
+.Sh CAVEATS
+The original 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.
.Sh HISTORY
.Nm
is based on the rcp program in
.Bx
source code from the Regents of the University of California.
+.Pp
+Since OpenSSH 8.8 (8.7 in Red Hat/Fedora builds),
+.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
diff --git a/scp.c b/scp.c
index e039350c..c7cf7529 100644
--- a/scp.c
+++ b/scp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: scp.c,v 1.232 2021/08/11 14:07:54 naddy Exp $ */
+/* $OpenBSD: scp.c,v 1.233 2021/09/08 23:31:39 djm Exp $ */
/*
* scp - secure remote copy. This is basically patched BSD rcp which
* uses ssh to do the data transfer (instead of using rcmd).
@@ -448,7 +448,7 @@ 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 */
@@ -1983,7 +1983,7 @@ void
usage(void)
{
(void) fprintf(stderr,
- "usage: scp [-346ABCOpqRrsTv] [-c cipher] [-D sftp_server_path] [-F ssh_config]\n"
+ "usage: scp [-346ABCOpqRrTv] [-c cipher] [-D sftp_server_path] [-F ssh_config]\n"
" [-i identity_file] [-J destination] [-l limit]\n"
" [-o ssh_option] [-P port] [-S program] source ... target\n");
exit(1);

11
openssh.spec
View File

@ -193,6 +193,10 @@ Patch966: openssh-8.2p1-x11-without-ipv6.patch
Patch974: openssh-8.0p1-keygen-strip-doseol.patch
# sshd provides PAM an incorrect error code (#1879503)
Patch975: openssh-8.0p1-preserve-pam-errors.patch
# Use SFTP protocol by default for scp command
Patch976: openssh-8.7p1-sftp-default-protocol.patch
# Implement kill switch for SCP protocol
Patch977: openssh-8.7p1-scp-kill-switch.patch
License: BSD
Requires: /sbin/nologin
@ -368,6 +372,8 @@ popd
%patch966 -p1 -b .x11-ipv6
%patch974 -p1 -b .keygen-strip-doseol
%patch975 -p1 -b .preserve-pam-errors
%patch976 -p1 -b .sftp-by-default
%patch977 -p1 -b .kill-scp
%patch200 -p1 -b .audit
%patch201 -p1 -b .audit-race
@ -653,7 +659,10 @@ test -f %{sysconfig_anaconda} && \
%changelog
* Fri Sep 24 2021 Dmitry Belyavskiy <dbelyavs@redhat.com> - 8.7p1-1 + 0.10.4-4
- New upstream release (#2001002)
- New upstream release
- Switch to SFTP protocol in scp utility by default
- Enable SCP protocol kill switch
Related: rhbz#2001002
* Mon Aug 09 2021 Mohan Boddu <mboddu@redhat.com> - 8.6p1-7.1
- Rebuilt for IMA sigs, glibc 2.34, aarch64 flags