Without the change test-dpp fails on aarch64-linux as:
$ unit/test-dpp
TEST: DPP test responder-only key derivation
TEST: DPP test mutual key derivation
TEST: DPP test PKEX key derivation
test-dpp: unit/test-dpp.c:514: test_pkex_key_derivation: Assertion `!memcmp(tmp, __tmp, 32)' failed.
This happens due to int/size_t type mismatch passed to vararg
parameters to prf_plus():
bool prf_plus(enum l_checksum_type type, const void *key, size_t key_len,
void *out, size_t out_len,
size_t n_extra, ...)
{
// ...
va_start(va, n_extra);
for (i = 0; i < n_extra; i++) {
iov[i + 1].iov_base = va_arg(va, void *);
iov[i + 1].iov_len = va_arg(va, size_t);
// ...
Note that varargs here could only be a sequence of `void *` / `size_t`
values.
But in src/dpp-util.c `iwd` attempted to pass `int` there:
prf_plus(sha, prk, bytes, z_out, bytes, 5,
mac_i, 6, // <- here
mac_r, 6, // <- and here
m_x, bytes,
n_x, bytes,
key, strlen(key));
aarch64 stores only 32-bit value part of the register:
mov w7, #0x6
str w7, [sp, #...]
and loads full 64-bit form of the register:
ldr x3, [x3]
As a result higher bits of `iov[].iov_len` contain unexpected values and
sendmsg sends a lot more data than expected to the kernel.
The change fixes test-dpp test for me.
While at it fixed obvious `int` / `size_t` mismatch in src/erp.c.
Fixes: 6320d6db0f ("crypto: remove label from prf_plus, instead use va_args")
ssid is declared as a 32 byte field in handshake_state, hence using it
as a string which is assumed to be nul-terminated will fail for SSIDs
that are 32 bytes long.
Fixes: d938d362b2 ("erp: ERP implementation and key cache move")
Fixes: 433373fe28 ("eapol: cache ERP keys on EAP success")
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.
src/erp.c:134:10: error: comparison of integer expressions of different
signedness: 'unsigned int' and 'int' [-Werror=sign-compare]
src/eap-ttls.c:378:10: error: comparison of integer expressions of different signedness: 'uint32_t' {aka 'unsigned int'} and 'int' [-Werror=sign-compare]
The intent of this check is to make sure that at least 2 bytes are
available for reading. However, the unintended consequence is that tags
with a zero length at the end of input would be rejected.
While here, rework the check to be more resistant to potential
overflow conditions.
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.
Since ERP is only used for FILS and not behaving in the 'normal' ERP
fashion (dealing with actual EAP data, timeouts etc.) we can structure
ERP as a more synchronous protocol, removing the need for a complete
callback.
Now, erp_rx_packet returns a status, so FILS can decide how to handle
any failures. The complete callback was also removed in favor of a
getter for the RMSK (erp_get_rmsk). This allows FILS to syncronously
handle ERP, and potentially fail directly in fils_rx_authenticate.
ERP (EAP Reauthentication Protocol) allows a station to quickly
reauthenticate using keys from a previous EAP authentication.
This change both implements ERP as well as moves the key cache into
the ERP module.
ERP in its current form is here to only support FILS. ERP is likely not
widespread and there is no easy way to determine if an AP supports ERP
without trying it. Attempting ERP with a non-ERP enabled AP will actually
result in longer connection times since ERP must fail and then full EAP
is done afterwards. For this reason ERP was separated from EAP and a
separate ERP state machine must be created. As it stands now, ERP cannot
be used on its own, only with FILS.
