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Message-ID: <3D6E02F3.1000604@d2.net.au> From: andrewg at d2.net.au (Andrew Griffiths) Subject: RPM verification -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Product: rpm Version tested: 4.0.4 Description - ----------- rpm is a powerful Package Manager, which can be used to ~ build, install, query, verify, update, and erase individ- ~ ual software packages. A package consists of an archive ~ of files and meta-data used to install and erase the ~ archive files. The meta-data includes helper scripts, file ~ attributes, and descriptive information about the package. ~ Packages come in two varieties: binary packages, used to ~ encapsulate software to be installed, and source packages, ~ containing the source code and recipe necessary to produce ~ binary packages. Problem - ------- The user can be tricked by thinking that the package came from a trusted source if the user either has gpg setup to automatically fetch keys from a keyserver (and the attacker knows, or spams to a majority) or the attacker initiates a conversation with the victim and the victim puts the attackers public key in the same gpg database which does the verification of the signed rpm package. Example - ------- [andrewg@...ckhole rpmzap]$ wget ftp://ftp.planetmirror.com/pub/redhat/redhat-7.3/en/os/i386/RedHat/RPMS/xloadimage-4.1-21.i386.rpm - --22:18:59-- ftp://ftp.planetmirror.com/pub/redhat/redhat-7.3/en/os/i386/RedHat/RPMS/xloadimage-4.1-21.i386.rpm ~ => `xloadimage-4.1-21.i386.rpm' Connecting to 127.0.0.1:3128... connected! Proxy request sent, awaiting response... 200 OK Length: 141,295 [audio/x-pn-realaudio-plugin] ~ 0K -> .......... .......... .......... .......... .......... [ 36%] ~ 50K -> .......... .......... .......... .......... .......... [ 72%] ~ 100K -> .......... .......... .......... ....... [100%] 22:18:59 (6.74 MB/s) - `xloadimage-4.1-21.i386.rpm' saved [141295/141295] ( Here, I have done a squid redirection to insert the trojaned file. We verify the downloaded RPM's as listed on RedHats GPG as of Thu Aug 22 10:59:09 EST 2002, with rpm --checksig, or its equivalent, rpm -K. http://www.redhat.com/solutions/security/news/publickey.html http://www.redhat.com/solutions/security/news/betapublickey.html Both listed the way to verify an rpm package, was to do rpm --checksig. Also, a lot of other distros recommend --checksig to verify. Some documentation needs to be updated. ) [andrewg@...ckhole rpmzap]$ rpm -K xloadimage-4.1-21.i386.rpm xloadimage-4.1-21.i386.rpm: md5 gpg OK (Everything looks fine... but..) [andrewg@...ckhole rpmzap]$ rpm -K xloadimage-4.1-21.i386.rpm -vv D: Expected size: 141295 = lead(96)+sigs(248)+pad(0)+data(140951) D: Actual size: 141295 xloadimage-4.1-21.i386.rpm: MD5 sum OK: 2bd4c89da85d38f279974d3707e721e3 gpg: Signature made Mon 19 Aug 2002 20:07:22 EST using DSA key ID 5A98A001 gpg: Good signature from Andrew Griffiths (...) <nullptr@...mail.com>" [andrewg@...ckhole rpmzap]$ (Not signed by RedHat... but the victim most likely doesn't think to check _who_ signed it.) Fix(es) - ------- - - Seperate gpg directory for GPG. For your ${HOME}, we'd do something like: mkdir .gpg-rpm chmod 700 .gpg-rpm rpm --import --homedir=${HOME}/.gpg-rpm RPM-GPG-KEY now we edit ${HOME}/.rpmmacros, and add/modify %_signature gpg %_gpg_path _your_home_dir_here/.gpg-rpm This way you can have seperate verification thingers, and rpm will automatically check the new setup. As such, the fix is to wait until RPM 4.1, which fixes the problem. Workarounds - ----------- - - Maybe parsing gpg's output and printing out signing keyname by default. - - Whenever you check the packages, use say --checksig -vv to get the output from gpg. Notes - ----- - - RedHat Network isn't vulnerable to this issue, as it does the setup like the above. - - Future versions of RPM (4.1) will not be using gpg externally, but will be maintaining the keys to verify internally. - - Following notification to Red Hat, they updated their verification instructions to include the use of the -v flag. - - Following notification to OpenPKG, they updated their security page, and their security advisory page. - - SuSE recommends to verify with rpm -v --checksig file.rpm. They were not contacted. - - Caldera didn't appear to offer a gpg signature to verify the rpm's. They didn't have a public key to encrypt stuff to them. Greets - ------ zen-parse - http://mp3.com/cosv jaguar remedy sharrad - http://go.to/innerdreams -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAj1uAvIACgkQoAeEnVqYoAH4vwCeLbmG8/HNKOtLpv+zmxIYPiJg EoAAoKxgfHlAwIfMpgBFUI1GAfG+Zggm =q3lj -----END PGP SIGNATURE-----
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