Fernando Arnaboldi from IOActive found several conditions in
which the server did not properly throw out maliciously constructed
variables in the access.conf file. This has been fixed along with new
fuzzing tests in the test suite.
Two bugs are fixed with this commit: verify permissions/ownership on the
fwknop.pid file only if it exists, and ensure to ru-run stat() on any directory
component if we're creating a directory.
- [client+server] Fernando Arnaboldi from IOActive found that strict
filesystem permissions for various fwknop files are not verified. Added
warnings whenever permissions are not strict enough, and ensured that
files created by the fwknop client and server are only set to user
read/write.
- [client] Fernando Arnaboldi from IOActive found a local buffer overflow
in --last processing with a maliciously constructed ~/.fwknop.run file.
This has been fixed with proper validation of .fwknop.run arguments.
This commit fixes a condition in which the server did not properly validate
allow IP addresses from malicious authenticated clients. This has been fixed
with stronger allow IP validation.
- [server] Fernando Arnaboldi from IOActive found several DoS/code
execution vulnerabilities for malicious fwknop clients that manage to
get past the authentication stage (so a such a client must be in
possession of a valid access.conf encryption key). These vulnerbilities
manifested themselves in the handling of malformed access requests, and
both the fwknopd server code along with libfko now perform stronger input
validation of access request data. These vulnerabilities affect
pre-2.0.3 fwknop releases.
- [test suite] Added a new fuzzing capability to ensure proper server-side
input validation. Fuzzing data is constructed with modified fwknop
client code that is designed to emulate malicious behavior.
Chop any trailing '/' char, be more careful about handling incoming large HTTP
responses, print the HTTP request and response in --verbose --verbose mode.
Updated the 'make install' step to not overwrite any existing config files in
/etc/fwknop/ and instead install new copies from the source tree at
/etc/fwknop/fwknopd.conf.inst and /etc/fwknop/access.conf.inst
Set restrictive permissions on /etc/fwknop/ directory and /etc/fwknop/* files.
Current default permissions on /etc/fwknop/ and /etc/fwknop/* are too lax.
Implemented a new check to ensure that the iptables 'comment' match exists to
ensure the proper environment for fwknopd operations. This check is controlled
by the new ENABLE_IPT_COMMENT_CHECK variable, and was suggested by Hank
Leininger.
For GPG mode, added a new access.conf variable "GPG_ALLOW_NO_PW" to make it
possible to leverage a server-side GPG key pair that has no associated
password. This comes in handy when a system requires the user to leverage
gpg-agent / pinentry which can present a problem in automated environments as
required by the fwknopd server. Now, it might seem like a problem to remove
the passphrase from a GPG key pair, but it's important to note that simply
doing this is little worse than storing the passphrase in the clear on disk
anyway in the access.conf file. Further, this link help provides additional
detail:
http://www.gnupg.org/faq/GnuPG-FAQ.html#how-can-i-use-gnupg-in-an-automated-environment
