Fix key derivation for Suite B 192-bit AKM to use SHA384

While the EAPOL-Key MIC derivation was already changed from SHA256 to
SHA384 for the Suite B 192-bit AKM, KDF had not been updated similarly.
Fix this by using HMAC-SHA384 instead of HMAC-SHA256 when deriving PTK
from PMK when using the Suite B 192-bit AKM.

Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/hostapd/Android.mk b/hostapd/Android.mk
index 28f443c..5885f2b 100644 (file)
--- a/hostapd/Android.mk
+++ b/hostapd/Android.mk
@@ -806,6 +806,7 @@ endif
 endif
 ifdef NEED_SHA384
 L_CFLAGS += -DCONFIG_SHA384
+OBJS += src/crypto/sha384-prf.c
 endif
 
 ifdef NEED_DH_GROUPS

diff --git a/hostapd/Makefile b/hostapd/Makefile
index 58213bb..a812b9d 100644 (file)
--- a/hostapd/Makefile
+++ b/hostapd/Makefile
@@ -791,6 +791,7 @@ endif
 endif
 ifdef NEED_SHA384
 CFLAGS += -DCONFIG_SHA384
+OBJS += ../src/crypto/sha384-prf.o
 endif
 
 ifdef NEED_DH_GROUPS

diff --git a/src/common/wpa_common.c b/src/common/wpa_common.c
index 0492810..e9d4248 100644 (file)
--- a/src/common/wpa_common.c
+++ b/src/common/wpa_common.c
@@ -170,6 +170,12 @@ int wpa_pmk_to_ptk(const u8 *pmk, size_t pmk_len, const char *label,
        ptk->tk_len = wpa_cipher_key_len(cipher);
        ptk_len = ptk->kck_len + ptk->kek_len + ptk->tk_len;
 
+#ifdef CONFIG_SUITEB192
+       if (wpa_key_mgmt_sha384(akmp))
+               sha384_prf(pmk, pmk_len, label, data, sizeof(data),
+                          tmp, ptk_len);
+       else
+#endif /* CONFIG_SUITEB192 */
 #ifdef CONFIG_IEEE80211W
        if (wpa_key_mgmt_sha256(akmp))
                sha256_prf(pmk, pmk_len, label, data, sizeof(data),

diff --git a/src/crypto/sha384-prf.c b/src/crypto/sha384-prf.c
new file mode 100644 (file)
index 0000000..653920b
--- /dev/null
+++ b/src/crypto/sha384-prf.c
@@ -0,0 +1,100 @@
+/*
+ * SHA384-based KDF (IEEE 802.11ac)
+ * Copyright (c) 2003-2015, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "includes.h"
+
+#include "common.h"
+#include "sha384.h"
+#include "crypto.h"
+
+
+/**
+ * sha384_prf - SHA384-based Key derivation function (IEEE 802.11ac, 11.6.1.7.2)
+ * @key: Key for KDF
+ * @key_len: Length of the key in bytes
+ * @label: A unique label for each purpose of the PRF
+ * @data: Extra data to bind into the key
+ * @data_len: Length of the data
+ * @buf: Buffer for the generated pseudo-random key
+ * @buf_len: Number of bytes of key to generate
+ *
+ * This function is used to derive new, cryptographically separate keys from a
+ * given key.
+ */
+void sha384_prf(const u8 *key, size_t key_len, const char *label,
+               const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
+{
+       sha384_prf_bits(key, key_len, label, data, data_len, buf, buf_len * 8);
+}
+
+
+/**
+ * sha384_prf_bits - IEEE Std 802.11ac-2013, 11.6.1.7.2 Key derivation function
+ * @key: Key for KDF
+ * @key_len: Length of the key in bytes
+ * @label: A unique label for each purpose of the PRF
+ * @data: Extra data to bind into the key
+ * @data_len: Length of the data
+ * @buf: Buffer for the generated pseudo-random key
+ * @buf_len: Number of bits of key to generate
+ *
+ * This function is used to derive new, cryptographically separate keys from a
+ * given key. If the requested buf_len is not divisible by eight, the least
+ * significant 1-7 bits of the last octet in the output are not part of the
+ * requested output.
+ */
+void sha384_prf_bits(const u8 *key, size_t key_len, const char *label,
+                    const u8 *data, size_t data_len, u8 *buf,
+                    size_t buf_len_bits)
+{
+       u16 counter = 1;
+       size_t pos, plen;
+       u8 hash[SHA384_MAC_LEN];
+       const u8 *addr[4];
+       size_t len[4];
+       u8 counter_le[2], length_le[2];
+       size_t buf_len = (buf_len_bits + 7) / 8;
+
+       addr[0] = counter_le;
+       len[0] = 2;
+       addr[1] = (u8 *) label;
+       len[1] = os_strlen(label);
+       addr[2] = data;
+       len[2] = data_len;
+       addr[3] = length_le;
+       len[3] = sizeof(length_le);
+
+       WPA_PUT_LE16(length_le, buf_len_bits);
+       pos = 0;
+       while (pos < buf_len) {
+               plen = buf_len - pos;
+               WPA_PUT_LE16(counter_le, counter);
+               if (plen >= SHA384_MAC_LEN) {
+                       hmac_sha384_vector(key, key_len, 4, addr, len,
+                                          &buf[pos]);
+                       pos += SHA384_MAC_LEN;
+               } else {
+                       hmac_sha384_vector(key, key_len, 4, addr, len, hash);
+                       os_memcpy(&buf[pos], hash, plen);
+                       pos += plen;
+                       break;
+               }
+               counter++;
+       }
+
+       /*
+        * Mask out unused bits in the last octet if it does not use all the
+        * bits.
+        */
+       if (buf_len_bits % 8) {
+               u8 mask = 0xff << (8 - buf_len_bits % 8);
+               buf[pos - 1] &= mask;
+       }
+
+       os_memset(hash, 0, sizeof(hash));
+}

diff --git a/src/crypto/sha384.h b/src/crypto/sha384.h
index e6a1fe4..3deafa5 100644 (file)
--- a/src/crypto/sha384.h
+++ b/src/crypto/sha384.h
@@ -15,5 +15,10 @@ int hmac_sha384_vector(const u8 *key, size_t key_len, size_t num_elem,
                       const u8 *addr[], const size_t *len, u8 *mac);
 int hmac_sha384(const u8 *key, size_t key_len, const u8 *data,
                size_t data_len, u8 *mac);
+void sha384_prf(const u8 *key, size_t key_len, const char *label,
+               const u8 *data, size_t data_len, u8 *buf, size_t buf_len);
+void sha384_prf_bits(const u8 *key, size_t key_len, const char *label,
+                    const u8 *data, size_t data_len, u8 *buf,
+                    size_t buf_len_bits);
 
 #endif /* SHA384_H */

diff --git a/wpa_supplicant/Android.mk b/wpa_supplicant/Android.mk
index 3673ba7..e235140 100644 (file)
--- a/wpa_supplicant/Android.mk
+++ b/wpa_supplicant/Android.mk
@@ -1282,6 +1282,7 @@ OBJS += $(SHA256OBJS)
 endif
 ifdef NEED_SHA384
 L_CFLAGS += -DCONFIG_SHA384
+OBJS += src/crypto/sha384-prf.c
 endif
 
 ifdef NEED_DH_GROUPS

diff --git a/wpa_supplicant/Makefile b/wpa_supplicant/Makefile
index 1f1527a..1597412 100644 (file)
--- a/wpa_supplicant/Makefile
+++ b/wpa_supplicant/Makefile
@@ -1293,6 +1293,7 @@ OBJS += $(SHA256OBJS)
 endif
 ifdef NEED_SHA384
 CFLAGS += -DCONFIG_SHA384
+OBJS += ../src/crypto/sha384-prf.o
 endif
 
 ifdef NEED_DH_GROUPS