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FreeBSD Errata Notice FreeBSD-EN-19:10.scp

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FreeBSD-EN-19:10.scp                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Insufficient filename validation in scp(1) client

Category:       contrib
Module:         scp
Announced:      2019-05-14
Affects:        All supported versions of FreeBSD.
Corrected:      2019-05-07 19:48:39 UTC (stable/12, 12.0-STABLE)
                2019-05-14 22:54:17 UTC (releng/12.0, 12.0-RELEASE-p10)
CVE Name:       CVE-2019-6111

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

scp(1) is a file transfer protocol running over an SSH session.

II.  Problem Description

The scp(1) client implementation fails to verify if the objects returned by
the server match what was requested.

III. Impact

A malicious scp server can write arbitrary files to the client.

IV.  Workaround

Switch to using the sftp(1) client, if possible.

V.   Solution

Note: While stable/11 and its release branches are currently affected by this
errata, due to the lack of patches, no fix is currently available for
stable/11.  We are currently evaluating a backport for these fixes to
stable/11.

Perform one of the following:

1) Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

2) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

3) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 12.0]
# fetch https://security.FreeBSD.org/patches/EN-19:10/scp.patch
# fetch https://security.FreeBSD.org/patches/EN-19:10/scp.patch.asc
# gpg --verify scp.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r347232
releng/12.0/                                                      r347586
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6111>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-19:10.scp.asc>
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