The prf_plus API was a bit restrictive because it only took a
string label which isn't compatible with some specs (e.g. DPP
inputs to HKDF-Expand). In addition it took additional label
aruments which were appended to the HMAC call (and the
non-intuitive '\0' if there were extra arguments).
Instead the label argument has been removed and callers can pass
it in through va_args. This also lets the caller decided the length
and can include the '\0' or not, dependent on the spec the caller
is following.
The existing API was limited to SHA1 or SHA256 and assumed a key
length of 32 bytes. Since other AKMs plan to be added update
this to take the checksum/length directly for better flexibility.
- Mostly problems with whitespace:
- Use of spaces instead of tabs
- Stray spaces before closing ')
- Missing spaces
- Missing 'void' from function declarations & definitions that
take no arguments.
- Wrong indentation level
PRF+ from RFC 5295 is the more generic function using which HKDF_Expand
is defined. Allow this function to take a vararg list of arguments to
be hashed (these are referred to as 'S' in the RFCs).
Implement hkdf_expand in terms of prf_plus and update all uses to the
new syntax.
Incorporate the LGPL v2.1 licensed implementation of ARC4, taken from
the Nettle project (https://git.lysator.liu.se/nettle/nettle.git,
commit 3e7a480a1e351884), and tweak it a bit so we don't have to
operate on a skip buffer to fast forward the stream cipher, but can
simply invoke it with NULL dst or src arguments to achieve the same.
This removes the dependency [via libell] on the OS's implementation of
ecb(arc4), which may be going away, and which is not usually accelerated
in the first place.
crypto_derive_pairwise_ptk was taking a boolean to decide whether to
use SHA1 or SHA256, but for FILS SHA384 may also be required for
rekeys depending on the AKM.
crypto_derive_pairwise_ptk was changed to take l_checksum_type instead
of a boolean to allow for all 3 SHA types.
If the input length is 16 bytes, this means aes_siv_decrypt should
only be verifying the 16 byte SIV and not decrypting any data. If
this is the case, we can skip over the whole AES-CTR portion of
AES-SIV and only verify the SIV.
Replace existing uses of memset to clear secrets with explicit_bzero to
make sure it doesn't get optimized away. This has some side effects as
documented in gcc docs but is still recommended.
In eap_secret_info_free make sure we clear both strings in the case of
EAP_SECRET_REMOTE_USER_PASSWORD secrets.
Remove an unneeded buffer and its memcpy, remove the now unneeded use of
l_checksum_digest_length and use l_checksum_reset instead of creating a
new l_checksum for each chunk.
Rather than hard coding to SHA256, we can pass in l_checksum_type
and use that SHA. This will allow for OWE/SAE/PWD to support more
curves that use different SHA algorithms for hashing.
Right now the PMK is hard coded to 32 bytes, which works for the vast
majority of cases. The only outlier is OWE which can generate a PMK
of 32, 48 or 64 bytes depending on the ECC group used. The PMK length
is already stored in the handshake, so now we can just pass that to
crypto_derive_pairwise_ptk
The crypto_ptk was hard coded for 16 byte KCK/KEK. Depending on the
AKM these can be up to 32 bytes. This changes completely removes the
crypto_ptk struct and adds getters to the handshake object for the
kck and kek. Like before the PTK is derived into a continuous buffer,
and the kck/kek getters take care of returning the proper key offset
depending on AKM.
To allow for larger than 16 byte keys aes_unwrap needed to be
modified to take the kek length.
The RFC (5869) for this implementation defines two functions,
HKDF-Extract and HKDF-Expand. The existing 'hkdf_256' was implementing
the Extract function, so it was renamed appropriately. The name was
changed for consistency when the Expand function will be added in the
future.
The "H" function used by SAE and EAP-PWD was effectively the same
function, EAP-PWD just used a zero key for its calls. This removes
the duplicate implementations and merges them into crypto.c as
"hkdf_256".
Since EAP-PWD always uses a zero'ed key, passing in a NULL key to
hkdf_256 will actually use a 32 byte zero'ed array as the key. This
avoids the need for EAP-PWD to store or create a zero'ed key for
every call.
Both the original "H" functions never called va_end, so that was
added to hkdf_256.
==40686== Syscall param sendmsg(msg.msg_iov[0]) points to uninitialised byte(s)
==40686== at 0x5147037: sendmsg (in /usr/lib64/libc-2.24.so)
==40686== by 0x43957C: operate_cipher (cipher.c:354)
==40686== by 0x439C18: l_cipher_decrypt (cipher.c:415)
==40686== by 0x40FAB8: arc4_skip (crypto.c:181)
Initialize the skip buffer to 0s. This isn't strictly necessary, but
hides the above valgrind warning.
The aim of arc4 skip is simply to seed some data into the RC4 cipher so
it makes it harder for the attacker to decrypt. This 'initialization'
doesn't really care what data is fed.
James Prestwood