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crypto: remove label from prf_plus, instead use va_args 

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.
This commit is contained in:
James Prestwood 2023-10-12 13:01:30 -07:00 committed by Denis Kenzior
parent 96587f3c8c
commit 6320d6db0f
3 changed files with 21 additions and 24 deletions
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24
src/crypto.c
View File

@ -624,10 +624,10 @@ bool prf_sha1(const void *key, size_t key_len,
/* PRF+ from RFC 5295 Section 3.1.2 (also RFC 4306 Section 2.13) */
bool prf_plus(enum l_checksum_type type, const void *key, size_t key_len,
const char *label, void *out, size_t out_len,
void *out, size_t out_len,
size_t n_extra, ...)
{
struct iovec iov[n_extra + 3];
struct iovec iov[n_extra + 2];
uint8_t *t = out;
size_t t_len = 0;
uint8_t count = 1;
@ -637,24 +637,17 @@ bool prf_plus(enum l_checksum_type type, const void *key, size_t key_len,
ssize_t ret;
size_t i;
iov[1].iov_base = (void *) label;
iov[1].iov_len = strlen(label);
/* Include the '\0' from the label in S if extra arguments provided */
if (n_extra)
iov[1].iov_len += 1;
va_start(va, n_extra);
for (i = 0; i < n_extra; i++) {
iov[i + 2].iov_base = va_arg(va, void *);
iov[i + 2].iov_len = va_arg(va, size_t);
iov[i + 1].iov_base = va_arg(va, void *);
iov[i + 1].iov_len = va_arg(va, size_t);
}
va_end(va);
iov[n_extra + 2].iov_base = &count;
iov[n_extra + 2].iov_len = 1;
iov[n_extra + 1].iov_base = &count;
iov[n_extra + 1].iov_len = 1;
hmac = l_checksum_new_hmac(type, key, key_len);
if (!hmac)
@ -664,7 +657,7 @@ bool prf_plus(enum l_checksum_type type, const void *key, size_t key_len,
iov[0].iov_base = t;
iov[0].iov_len = t_len;
if (!l_checksum_updatev(hmac, iov, n_extra + 3)) {
if (!l_checksum_updatev(hmac, iov, n_extra + 2)) {
l_checksum_free(hmac);
return false;
}
@ -874,7 +867,8 @@ bool hkdf_extract(enum l_checksum_type type, const void *key,
bool hkdf_expand(enum l_checksum_type type, const void *key, size_t key_len,
const char *info, void *out, size_t out_len)
{
return prf_plus(type, key, key_len, info, out, out_len, 0);
return prf_plus(type, key, key_len, out, out_len, 1,
info, strlen(info));
}
/*

2
src/crypto.h
View File

@ -122,7 +122,7 @@ bool prf_plus_sha1(const void *key, size_t key_len,
const void *data, size_t data_len, void *output, size_t size);
bool prf_plus(enum l_checksum_type type, const void *key, size_t key_len,
const char *label, void *out, size_t out_len,
void *out, size_t out_len,
size_t n_extra, ...);
bool hkdf_extract(enum l_checksum_type type, const void *key, size_t key_len,

19
src/erp.c
View File

@ -281,8 +281,9 @@ static bool erp_derive_emsk_name(const uint8_t *session_id, size_t session_len,
uint16_t eight = L_CPU_TO_BE16(8);
char *ascii;
if (!prf_plus(L_CHECKSUM_SHA256, session_id, session_len, "EMSK",
hex, 8, 1, &eight, sizeof(eight)))
if (!prf_plus(L_CHECKSUM_SHA256, session_id, session_len,
hex, 8, 2, "EMSK", strlen("EMSK") + 1,
&eight, sizeof(eight)))
return false;
ascii = l_util_hexstring(hex, 8);
@ -309,13 +310,15 @@ static bool erp_derive_reauth_keys(const uint8_t *emsk, size_t emsk_len,
uint16_t len = L_CPU_TO_BE16(emsk_len);
uint8_t cryptosuite = ERP_CRYPTOSUITE_SHA256_128;
if (!prf_plus(L_CHECKSUM_SHA256, emsk, emsk_len, ERP_RRK_LABEL,
r_rk, emsk_len, 1,
if (!prf_plus(L_CHECKSUM_SHA256, emsk, emsk_len,
r_rk, emsk_len, 2, ERP_RRK_LABEL,
strlen(ERP_RRK_LABEL) + 1,
&len, sizeof(len)))
return false;
if (!prf_plus(L_CHECKSUM_SHA256, r_rk, emsk_len, ERP_RIK_LABEL,
r_ik, emsk_len, 2,
if (!prf_plus(L_CHECKSUM_SHA256, r_rk, emsk_len,
r_ik, emsk_len, 3, ERP_RIK_LABEL,
strlen(ERP_RIK_LABEL) + 1,
&cryptosuite, 1, &len, sizeof(len)))
return false;
@ -496,8 +499,8 @@ int erp_rx_packet(struct erp_state *erp, const uint8_t *pkt, size_t len)
length = L_CPU_TO_BE16(64);
if (!prf_plus(L_CHECKSUM_SHA256, erp->r_rk, erp->cache->emsk_len,
ERP_RMSK_LABEL,
erp->rmsk, erp->cache->emsk_len, 2,
erp->rmsk, erp->cache->emsk_len, 3,
ERP_RMSK_LABEL, strlen(ERP_RMSK_LABEL) + 1,
&seq, sizeof(seq),
&length, sizeof(length)))
goto eap_failed;