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A few weeks ago, I added some code to cifs.upcall to take the pid sent
by the kernel and use that to get the value of the $KRB5CCNAME
environment var for the process. That works fine on the initial mount,
but could be problematic on reconnect.
There's no guarantee on a reconnect that the process that initiates the
upcall will have $KRB5CCNAME pointed at the correct credcache. Because
of this, the current scheme isn't going to be reliable enough and we
need to use something different.
This patch replaces that scheme with one very similar to the one used by
rpc.gssd in nfs-utils. It searches the credcache dir (currently
hardcoded to /tmp) for a valid credcache for the given uid. If it finds
one then it uses that as the credentials cache. If it finds more than
one, it uses the one with the latest TGT expiration.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Igor Mammedov pointed out that reverse resolving an IP address to get
the hostname portion of a principal could open a possible attack
vector. If an attacker were to gain control of DNS, then he could
redirect the mount to a server of his choosing, and fix the reverse
resolution to point to a hostname of his choosing (one where he has
the key for the corresponding cifs/ or host/ principal).
That said, we often trust DNS for other reasons and it can be useful
to do so. Make the code that allows trusting DNS to be enabled by
adding --trust-dns to the cifs.upcall invocation.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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...to allow long option names.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Current kernels don't send IPv6 addresses with the colon delimiters, add
a routine to add them when they're not present.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Instead of using the hostname given by the upcall to get the server's
principal, take the IP address given in the upcall and reverse resolve
it to a hostname.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Add a new stack var to hold the flags returned by the decoder routine
so that we don't need to worry so much about preserving "rc".
With this, we can drop privs before trying to find the location of
the credcache.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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cifs.upcall takes a "-c" flag that tells the upcall to get a principal
in the form of "cifs/hostname.example.com@REALM" instead of
"host/hostname.example.com@REALM". This has turned out to be a source of
great confusion for users.
Instead of requiring this flag, have the upcall try to get a "cifs/"
principal first. If that fails, fall back to getting a "host/"
principal.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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The argument list for the decoder is becoming rather long. Declare an
args structure and use that for holding the args. This also simplifies
pointer handling a bit.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Clean up some unneeded curly braces, and fix some indentation.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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Change the log levels to be more appropriate to the messages being
logged. Error messages should be LOG_ERR and not LOG_WARNING, for
instance.
Add some LOG_DEBUG messages that we can use to diagnose problems with
krb5 upcalls. With these, someone can set up syslog to log daemon.debug
and should be able to get more info when things aren't working.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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If the kernel sends the upcall a pid of the requesting process, we can
open that process' /proc/<pid>/environ file and scrape the KRB5CCNAME
value out of it.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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in Samba 4.
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