Messages in this thread | | | Subject | Re: [PATCH v5] KEYS: encrypted: fix key instantiation with user-provided data | From | Mimi Zohar <> | Date | Wed, 19 Oct 2022 12:31:47 -0400 |
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Hi Nikolaus,
On Wed, 2022-10-19 at 16:07 +0200, Nikolaus Voss wrote: > Commit cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-provided > decrypted data") added key instantiation with user provided decrypted data. > The user data is hex-ascii-encoded but was just memcpy'ed to the binary buffer. > Fix this to use hex2bin instead. > > Old keys created from user provided decrypted data saved with "keyctl pipe" > are still valid, however if the key is recreated from decrypted data the > old key must be converted to the correct format. This can be done with a > small shell script, e.g.: > > BROKENKEY=abcdefABCDEF1234567890aaaaaaaaaa > NEWKEY=$(echo -ne $BROKENKEY | xxd -p -c32) > keyctl add user masterkey "$(cat masterkey.bin)" @u > keyctl add encrypted testkey "new user:masterkey 32 $NEWKEY" @u > > However, NEWKEY is still broken: If for BROKENKEY 32 bytes were specified, a > brute force attacker knowing the key properties would only need to try at most > 2^(16*8) keys, as if the key was only 16 bytes long. > > The security issue is a result of the combination of limiting the input range > to hex-ascii and using memcpy() instead of hex2bin(). It could have been fixed > either by allowing binary input or using hex2bin() (and doubling the ascii > input key length). This patch implements the latter. > > The corresponding test for the Linux Test Project ltp has also been > fixed (see link below). > > Fixes: cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-provided decrypted data") > Cc: stable <stable@kernel.org> > Link: https://lore.kernel.org/ltp/20221006081709.92303897@mail.steuer-voss.de/ > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > Signed-off-by: Nikolaus Voss <nikolaus.voss@haag-streit.com>
While preparing to queue this patch, I noticed scripts/checkpatch.pl returns a couple of warnings, including that the sender email address and your tag here don't match. Wish I had caught them earlier. -- thanks,
Mimi
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