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rpc: avoid ssh interpreting malicious hostname as arguments

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Inspired by the recent GIT / Mercurial security flaws
(http://blog.recurity-labs.com/2017-08-10/scm-vulns),
consider someone/something manages to feed libvirt a bogus
URI such as:

  virsh -c qemu+ssh://-oProxyCommand=gnome-calculator/system

In this case, the hosname "-oProxyCommand=gnome-calculator"
will get interpreted as an argument to ssh, not a hostname.
Fortunately, due to the set of args we have following the
hostname, SSH will then interpret our bit of shell script
that runs 'nc' on the remote host as a cipher name, which is
clearly invalid. This makes ssh exit during argv parsing and
so it never tries to run gnome-calculator.

We are lucky this time, but lets be more paranoid, by using
'--' to explicitly tell SSH when it has finished seeing
command line options. This forces it to interpret
"-oProxyCommand=gnome-calculator" as a hostname, and thus
see a fail from hostname lookup.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2017-08-11 17:19:53 +01:00
parent ed8661a309
commit e4cb850081
1 changed files with 1 additions and 1 deletions
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2
src/rpc/virnetsocket.c
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@ -868,7 +868,7 @@ int virNetSocketNewConnectSSH(const char *nodename,
if (!netcat) if (!netcat)
netcat = "nc"; netcat = "nc";
virCommandAddArgList(cmd, nodename, "sh", "-c", NULL); virCommandAddArgList(cmd, "--", nodename, "sh", "-c", NULL);
virBufferEscapeShell(&buf, netcat); virBufferEscapeShell(&buf, netcat);
if (virBufferCheckError(&buf) < 0) { if (virBufferCheckError(&buf) < 0) {