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mka: AES-CMAC-256 -based KDF

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Extend the previously implemented KDF (IEEE Std 802.1X-2010, 6.2.1) to
support 256-bit input key and AES-CMAC-256. This does not change any
actual key derivation functionality yet, but is needed as a step towards
supporting 256-bit CAK.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2018-12-26 12:13:40 +02:00
parent a8aeaf41df
commit 9dd701c12e
1 changed files with 23 additions and 13 deletions
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24
src/pae/ieee802_1x_key.c
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@ -31,7 +31,8 @@ static void joint_two_mac(const u8 *mac1, const u8 *mac2, u8 *out)
/* IEEE Std 802.1X-2010, 6.2.1 KDF */ /* IEEE Std 802.1X-2010, 6.2.1 KDF */
static int aes_kdf_128(const u8 *kdk, const char *label, const u8 *context, static int aes_kdf(const u8 *kdk, size_t kdk_bits,
const char *label, const u8 *context,
int ctx_bits, int ret_bits, u8 *ret) int ctx_bits, int ret_bits, u8 *ret)
{ {
const int h = 128; const int h = 128;
@ -40,6 +41,9 @@ static int aes_kdf_128(const u8 *kdk, const char *label, const u8 *context,
int lab_len, ctx_len, ret_len, buf_len; int lab_len, ctx_len, ret_len, buf_len;
u8 *buf; u8 *buf;
if (kdk_bits != 128 && kdk_bits != 256)
return -1;
lab_len = os_strlen(label); lab_len = os_strlen(label);
ctx_len = (ctx_bits + 7) / 8; ctx_len = (ctx_bits + 7) / 8;
ret_len = ((ret_bits & 0xffff) + 7) / 8; ret_len = ((ret_bits & 0xffff) + 7) / 8;
@ -60,8 +64,14 @@ static int aes_kdf_128(const u8 *kdk, const char *label, const u8 *context,
WPA_PUT_BE16(&buf[buf_len - 2], ret_bits); WPA_PUT_BE16(&buf[buf_len - 2], ret_bits);
for (i = 0; i < n; i++) { for (i = 0; i < n; i++) {
int res;
buf[0] = (u8) (i + 1); buf[0] = (u8) (i + 1);
if (omac1_aes_128(kdk, buf, buf_len, ret)) { if (kdk_bits == 128)
res = omac1_aes_128(kdk, buf, buf_len, ret);
else
res = omac1_aes_256(kdk, buf, buf_len, ret);
if (res) {
os_free(buf); os_free(buf);
return -1; return -1;
} }
@ -85,7 +95,7 @@ int ieee802_1x_cak_128bits_aes_cmac(const u8 *msk, const u8 *mac1,
u8 context[2 * ETH_ALEN]; u8 context[2 * ETH_ALEN];
joint_two_mac(mac1, mac2, context); joint_two_mac(mac1, mac2, context);
return aes_kdf_128(msk, "IEEE8021 EAP CAK", return aes_kdf(msk, 128, "IEEE8021 EAP CAK",
context, sizeof(context) * 8, 128, cak); context, sizeof(context) * 8, 128, cak);
} }
@ -112,7 +122,7 @@ int ieee802_1x_ckn_128bits_aes_cmac(const u8 *msk, const u8 *mac1,
os_memcpy(context, sid, sid_bytes); os_memcpy(context, sid, sid_bytes);
joint_two_mac(mac1, mac2, context + sid_bytes); joint_two_mac(mac1, mac2, context + sid_bytes);
res = aes_kdf_128(msk, "IEEE8021 EAP CKN", context, ctx_len * 8, res = aes_kdf(msk, 128, "IEEE8021 EAP CKN", context, ctx_len * 8,
128, ckn); 128, ckn);
os_free(context); os_free(context);
return res; return res;
@ -134,7 +144,7 @@ int ieee802_1x_kek_128bits_aes_cmac(const u8 *cak, const u8 *ckn,
os_memset(context, 0, sizeof(context)); os_memset(context, 0, sizeof(context));
os_memcpy(context, ckn, (ckn_bytes < 16) ? ckn_bytes : 16); os_memcpy(context, ckn, (ckn_bytes < 16) ? ckn_bytes : 16);
return aes_kdf_128(cak, "IEEE8021 KEK", context, sizeof(context) * 8, return aes_kdf(cak, 128, "IEEE8021 KEK", context, sizeof(context) * 8,
128, kek); 128, kek);
} }
@ -154,7 +164,7 @@ int ieee802_1x_ick_128bits_aes_cmac(const u8 *cak, const u8 *ckn,
os_memset(context, 0, sizeof(context)); os_memset(context, 0, sizeof(context));
os_memcpy(context, ckn, (ckn_bytes < 16) ? ckn_bytes : 16); os_memcpy(context, ckn, (ckn_bytes < 16) ? ckn_bytes : 16);
return aes_kdf_128(cak, "IEEE8021 ICK", context, sizeof(context) * 8, return aes_kdf(cak, 128, "IEEE8021 ICK", context, sizeof(context) * 8,
128, ick); 128, ick);
} }
@ -185,6 +195,6 @@ int ieee802_1x_icv_128bits_aes_cmac(const u8 *ick, const u8 *msg,
int ieee802_1x_sak_128bits_aes_cmac(const u8 *cak, const u8 *ctx, int ieee802_1x_sak_128bits_aes_cmac(const u8 *cak, const u8 *ctx,
size_t ctx_bytes, u8 *sak, size_t sak_bytes) size_t ctx_bytes, u8 *sak, size_t sak_bytes)
{ {
return aes_kdf_128(cak, "IEEE8021 SAK", ctx, ctx_bytes * 8, return aes_kdf(cak, 128, "IEEE8021 SAK", ctx, ctx_bytes * 8,
sak_bytes * 8, sak); sak_bytes * 8, sak);
} }