/* $OpenBSD: ieee80211_crypto_tkip.c,v 1.9 2008/09/27 15:00:08 damien Exp $ */ /*- * Copyright (c) 2008 Damien Bergamini * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* * This code implements the Temporal Key Integrity Protocol (TKIP) defined * in IEEE Std 802.11-2007 section 8.3.2. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET #include #include #endif #include #include #include #include typedef u_int8_t byte; /* 8-bit byte (octet) */ typedef u_int16_t u16b; /* 16-bit unsigned word */ typedef u_int32_t u32b; /* 32-bit unsigned word */ static void Phase1(u16b *, const byte *, const byte *, u32b); static void Phase2(byte *, const byte *, const u16b *, u16b); /* TKIP software crypto context */ struct ieee80211_tkip_ctx { struct rc4_ctx rc4; const u_int8_t *txmic; const u_int8_t *rxmic; u_int16_t TTAK1[5]; u_int16_t TTAK2[5]; u_int8_t TTAK2ok; }; /* * Initialize software crypto context. This function can be overridden * by drivers doing hardware crypto. */ int ieee80211_tkip_set_key(struct ieee80211com *ic, struct ieee80211_key *k) { struct ieee80211_tkip_ctx *ctx; ctx = malloc(sizeof(*ctx), M_DEVBUF, M_NOWAIT | M_ZERO); if (ctx == NULL) return ENOMEM; /* * Use bits 128-191 as the Michael key for AA->SPA and bits * 192-255 as the Michael key for SPA->AA. */ #ifndef IEEE80211_STA_ONLY if (ic->ic_opmode == IEEE80211_M_HOSTAP) { ctx->txmic = &k->k_key[16]; ctx->rxmic = &k->k_key[24]; } else #endif { ctx->rxmic = &k->k_key[16]; ctx->txmic = &k->k_key[24]; } k->k_priv = ctx; return 0; } void ieee80211_tkip_delete_key(struct ieee80211com *ic, struct ieee80211_key *k) { if (k->k_priv != NULL) free(k->k_priv, M_DEVBUF); k->k_priv = NULL; } /* pseudo-header used for TKIP MIC computation */ struct ieee80211_tkip_frame { u_int8_t i_da[IEEE80211_ADDR_LEN]; u_int8_t i_sa[IEEE80211_ADDR_LEN]; u_int8_t i_pri; u_int8_t i_pad[3]; } __packed; /* * Compute TKIP MIC over an mbuf chain starting "off" bytes from the * beginning. This function should be kept independant from the software * TKIP crypto code so that drivers doing hardware crypto but not MIC can * call it without a software crypto context. */ void ieee80211_tkip_mic(struct mbuf *m0, int off, const u_int8_t *key, u_int8_t mic[IEEE80211_TKIP_MICLEN]) { const struct ieee80211_frame *wh; struct ieee80211_tkip_frame wht; MICHAEL_CTX ctx; /* small enough */ struct mbuf *m; caddr_t pos; int len; /* assumes 802.11 header is contiguous */ wh = mtod(m0, struct ieee80211_frame *); /* construct pseudo-header for TKIP MIC computation */ switch (wh->i_fc[1] & IEEE80211_FC1_DIR_MASK) { case IEEE80211_FC1_DIR_NODS: IEEE80211_ADDR_COPY(wht.i_da, wh->i_addr1); IEEE80211_ADDR_COPY(wht.i_sa, wh->i_addr2); break; case IEEE80211_FC1_DIR_TODS: IEEE80211_ADDR_COPY(wht.i_da, wh->i_addr3); IEEE80211_ADDR_COPY(wht.i_sa, wh->i_addr2); break; case IEEE80211_FC1_DIR_FROMDS: IEEE80211_ADDR_COPY(wht.i_da, wh->i_addr1); IEEE80211_ADDR_COPY(wht.i_sa, wh->i_addr3); break; case IEEE80211_FC1_DIR_DSTODS: IEEE80211_ADDR_COPY(wht.i_da, wh->i_addr3); IEEE80211_ADDR_COPY(wht.i_sa, ((const struct ieee80211_frame_addr4 *)wh)->i_addr4); break; } if (ieee80211_has_qos(wh)) wht.i_pri = ieee80211_get_qos(wh) & IEEE80211_QOS_TID; else wht.i_pri = 0; wht.i_pad[0] = wht.i_pad[1] = wht.i_pad[2] = 0; michael_init(&ctx); michael_key(key, &ctx); michael_update(&ctx, (caddr_t)&wht, sizeof(wht)); m = m0; /* assumes the first "off" bytes are contiguous */ pos = mtod(m, caddr_t) + off; len = m->m_len - off; for (;;) { michael_update(&ctx, pos, len); if ((m = m->m_next) == NULL) break; pos = mtod(m, caddr_t); len = m->m_len; } michael_final(mic, &ctx); } /* shortcuts */ #define IEEE80211_TKIP_TAILLEN \ (IEEE80211_TKIP_MICLEN + IEEE80211_WEP_CRCLEN) #define IEEE80211_TKIP_OVHD \ (IEEE80211_TKIP_HDRLEN + IEEE80211_TKIP_TAILLEN) struct mbuf * ieee80211_tkip_encrypt(struct ieee80211com *ic, struct mbuf *m0, struct ieee80211_key *k) { struct ieee80211_tkip_ctx *ctx = k->k_priv; u_int16_t wepseed[8]; /* needs to be 16-bit aligned for Phase2 */ const struct ieee80211_frame *wh; u_int8_t *ivp, *mic, *icvp; struct mbuf *n0, *m, *n; u_int32_t crc; int left, moff, noff, len, hdrlen; MGET(n0, M_DONTWAIT, m0->m_type); if (n0 == NULL) goto nospace; M_DUP_PKTHDR(n0, m0); n0->m_pkthdr.len += IEEE80211_TKIP_HDRLEN; n0->m_len = MHLEN; if (n0->m_pkthdr.len >= MINCLSIZE - IEEE80211_TKIP_TAILLEN) { MCLGET(n0, M_DONTWAIT); if (n0->m_flags & M_EXT) n0->m_len = n0->m_ext.ext_size; } if (n0->m_len > n0->m_pkthdr.len) n0->m_len = n0->m_pkthdr.len; /* copy 802.11 header */ wh = mtod(m0, struct ieee80211_frame *); hdrlen = ieee80211_get_hdrlen(wh); memcpy(mtod(n0, caddr_t), wh, hdrlen); /* construct TKIP header */ ivp = mtod(n0, u_int8_t *) + hdrlen; ivp[0] = k->k_tsc >> 8; /* TSC1 */ /* WEP Seed = (TSC1 | 0x20) & 0x7f (see 8.3.2.2) */ ivp[1] = (ivp[0] | 0x20) & 0x7f; ivp[2] = k->k_tsc; /* TSC0 */ ivp[3] = k->k_id << 6 | IEEE80211_WEP_EXTIV; /* KeyID | ExtIV */ ivp[4] = k->k_tsc >> 16; /* TSC2 */ ivp[5] = k->k_tsc >> 24; /* TSC3 */ ivp[6] = k->k_tsc >> 32; /* TSC4 */ ivp[7] = k->k_tsc >> 40; /* TSC5 */ /* compute WEP seed */ if ((k->k_tsc & 0xffff) == 0) Phase1(ctx->TTAK1, k->k_key, wh->i_addr2, k->k_tsc >> 16); Phase2((u_int8_t *)wepseed, k->k_key, ctx->TTAK1, k->k_tsc & 0xffff); rc4_keysetup(&ctx->rc4, (u_int8_t *)wepseed, 16); /* encrypt frame body and compute WEP ICV */ m = m0; n = n0; moff = hdrlen; noff = hdrlen + IEEE80211_TKIP_HDRLEN; left = m0->m_pkthdr.len - moff; crc = ~0; while (left > 0) { if (moff == m->m_len) { /* nothing left to copy from m */ m = m->m_next; moff = 0; } if (noff == n->m_len) { /* n is full and there's more data to copy */ MGET(n->m_next, M_DONTWAIT, n->m_type); if (n->m_next == NULL) goto nospace; n = n->m_next; n->m_len = MLEN; if (left >= MINCLSIZE - IEEE80211_TKIP_TAILLEN) { MCLGET(n, M_DONTWAIT); if (n->m_flags & M_EXT) n->m_len = n->m_ext.ext_size; } if (n->m_len > left) n->m_len = left; noff = 0; } len = min(m->m_len - moff, n->m_len - noff); crc = ether_crc32_le_update(crc, mtod(m, caddr_t) + moff, len); rc4_crypt(&ctx->rc4, mtod(m, caddr_t) + moff, mtod(n, caddr_t) + noff, len); moff += len; noff += len; left -= len; } /* reserve trailing space for TKIP MIC and WEP ICV */ if (M_TRAILINGSPACE(n) < IEEE80211_TKIP_TAILLEN) { MGET(n->m_next, M_DONTWAIT, n->m_type); if (n->m_next == NULL) goto nospace; n = n->m_next; n->m_len = 0; } /* compute TKIP MIC over clear text */ mic = mtod(n, caddr_t) + n->m_len; ieee80211_tkip_mic(m0, hdrlen, ctx->txmic, mic); crc = ether_crc32_le_update(crc, mic, IEEE80211_TKIP_MICLEN); rc4_crypt(&ctx->rc4, mic, mic, IEEE80211_TKIP_MICLEN); n->m_len += IEEE80211_TKIP_MICLEN; /* finalize WEP ICV */ icvp = mtod(n, caddr_t) + n->m_len; crc = ~crc; icvp[0] = crc; icvp[1] = crc >> 8; icvp[2] = crc >> 16; icvp[3] = crc >> 24; rc4_crypt(&ctx->rc4, icvp, icvp, IEEE80211_WEP_CRCLEN); n->m_len += IEEE80211_WEP_CRCLEN; n0->m_pkthdr.len += IEEE80211_TKIP_TAILLEN; k->k_tsc++; /* increment the 48-bit TSC */ m_freem(m0); return n0; nospace: ic->ic_stats.is_tx_nombuf++; m_freem(m0); if (n0 != NULL) m_freem(n0); return NULL; } struct mbuf * ieee80211_tkip_decrypt(struct ieee80211com *ic, struct mbuf *m0, struct ieee80211_key *k) { struct ieee80211_tkip_ctx *ctx = k->k_priv; struct ieee80211_frame *wh; u_int16_t wepseed[8]; /* needs to be 16-bit aligned for Phase2 */ u_int8_t buf[IEEE80211_TKIP_MICLEN + IEEE80211_WEP_CRCLEN]; u_int8_t mic[IEEE80211_TKIP_MICLEN]; u_int64_t tsc, *prsc; u_int32_t crc, crc0; u_int8_t *ivp, *mic0; u_int8_t tid; struct mbuf *n0, *m, *n; int hdrlen, left, moff, noff, len; wh = mtod(m0, struct ieee80211_frame *); hdrlen = ieee80211_get_hdrlen(wh); if (m0->m_pkthdr.len < hdrlen + IEEE80211_TKIP_OVHD) { m_freem(m0); return NULL; } ivp = (u_int8_t *)wh + hdrlen; /* check that ExtIV bit is be set */ if (!(ivp[3] & IEEE80211_WEP_EXTIV)) { m_freem(m0); return NULL; } /* retrieve last seen packet number for this frame priority */ tid = ieee80211_has_qos(wh) ? ieee80211_get_qos(wh) & IEEE80211_QOS_TID : 0; prsc = &k->k_rsc[tid]; /* extract the 48-bit TSC from the TKIP header */ tsc = (u_int64_t)ivp[2] | (u_int64_t)ivp[0] << 8 | (u_int64_t)ivp[4] << 16 | (u_int64_t)ivp[5] << 24 | (u_int64_t)ivp[6] << 32 | (u_int64_t)ivp[7] << 40; if (tsc <= *prsc) { /* replayed frame, discard */ ic->ic_stats.is_tkip_replays++; m_freem(m0); return NULL; } MGET(n0, M_DONTWAIT, m0->m_type); if (n0 == NULL) goto nospace; M_DUP_PKTHDR(n0, m0); n0->m_pkthdr.len -= IEEE80211_TKIP_OVHD; n0->m_len = MHLEN; if (n0->m_pkthdr.len >= MINCLSIZE) { MCLGET(n0, M_DONTWAIT); if (n0->m_flags & M_EXT) n0->m_len = n0->m_ext.ext_size; } if (n0->m_len > n0->m_pkthdr.len) n0->m_len = n0->m_pkthdr.len; /* copy 802.11 header and clear protected bit */ memcpy(mtod(n0, caddr_t), wh, hdrlen); wh = mtod(n0, struct ieee80211_frame *); wh->i_fc[1] &= ~IEEE80211_FC1_PROTECTED; /* compute WEP seed */ if (!ctx->TTAK2ok || ((tsc >> 16) != (*prsc >> 16))) { Phase1(ctx->TTAK2, k->k_key, wh->i_addr2, tsc >> 16); ctx->TTAK2ok = 1; } Phase2((u_int8_t *)wepseed, k->k_key, ctx->TTAK2, tsc & 0xffff); rc4_keysetup(&ctx->rc4, (u_int8_t *)wepseed, 16); /* decrypt frame body and compute WEP ICV */ m = m0; n = n0; moff = hdrlen + IEEE80211_TKIP_HDRLEN; noff = hdrlen; left = n0->m_pkthdr.len - noff; crc = ~0; while (left > 0) { if (moff == m->m_len) { /* nothing left to copy from m */ m = m->m_next; moff = 0; } if (noff == n->m_len) { /* n is full and there's more data to copy */ MGET(n->m_next, M_DONTWAIT, n->m_type); if (n->m_next == NULL) goto nospace; n = n->m_next; n->m_len = MLEN; if (left >= MINCLSIZE) { MCLGET(n, M_DONTWAIT); if (n->m_flags & M_EXT) n->m_len = n->m_ext.ext_size; } if (n->m_len > left) n->m_len = left; noff = 0; } len = min(m->m_len - moff, n->m_len - noff); rc4_crypt(&ctx->rc4, mtod(m, caddr_t) + moff, mtod(n, caddr_t) + noff, len); crc = ether_crc32_le_update(crc, mtod(n, caddr_t) + noff, len); moff += len; noff += len; left -= len; } /* extract and decrypt TKIP MIC and WEP ICV from m0's tail */ m_copydata(m, moff, IEEE80211_TKIP_TAILLEN, buf); rc4_crypt(&ctx->rc4, buf, buf, IEEE80211_TKIP_TAILLEN); /* include TKIP MIC in WEP ICV */ mic0 = buf; crc = ether_crc32_le_update(crc, mic0, IEEE80211_TKIP_MICLEN); crc = ~crc; /* decrypt ICV and compare it with calculated ICV */ crc0 = *(u_int32_t *)(buf + IEEE80211_TKIP_MICLEN); if (crc != letoh32(crc0)) { ic->ic_stats.is_tkip_icv_errs++; m_freem(m0); m_freem(n0); return NULL; } /* compute TKIP MIC over decrypted message */ ieee80211_tkip_mic(n0, hdrlen, ctx->rxmic, mic); /* check that it matches the MIC in received frame */ if (memcmp(mic0, mic, IEEE80211_TKIP_MICLEN) != 0) { m_freem(m0); m_freem(n0); ic->ic_stats.is_rx_locmicfail++; ieee80211_michael_mic_failure(ic, tsc); return NULL; } /* update last seen packet number (MIC is validated) */ *prsc = tsc; m_freem(m0); return n0; nospace: ic->ic_stats.is_rx_nombuf++; m_freem(m0); if (n0 != NULL) m_freem(n0); return NULL; } #ifndef IEEE80211_STA_ONLY /* * This function is called in HostAP mode to deauthenticate all STAs using * TKIP as their pairwise or group cipher (as part of TKIP countermeasures). */ static void ieee80211_tkip_deauth(void *arg, struct ieee80211_node *ni) { struct ieee80211com *ic = arg; if (ni->ni_state == IEEE80211_STA_ASSOC && (ic->ic_bss->ni_rsngroupcipher == IEEE80211_CIPHER_TKIP || ni->ni_rsncipher == IEEE80211_CIPHER_TKIP)) { /* deauthenticate STA */ IEEE80211_SEND_MGMT(ic, ni, IEEE80211_FC0_SUBTYPE_DEAUTH, IEEE80211_REASON_MIC_FAILURE); ieee80211_node_leave(ic, ni); } } #endif /* IEEE80211_STA_ONLY */ /* * This function can be called by the software TKIP crypto code or by the * drivers when their hardware crypto engines detect a Michael MIC failure. */ void ieee80211_michael_mic_failure(struct ieee80211com *ic, u_int64_t tsc) { extern int ticks; if (ic->ic_flags & IEEE80211_F_COUNTERM) return; /* countermeasures already active */ log(LOG_WARNING, "%s: Michael MIC failure", ic->ic_if.if_xname); if (ic->ic_opmode == IEEE80211_M_STA) { /* send a Michael MIC Failure Report frame to the AP */ (void)ieee80211_send_eapol_key_req(ic, ic->ic_bss, EAPOL_KEY_KEYMIC | EAPOL_KEY_ERROR | EAPOL_KEY_SECURE, tsc); } /* * Activate TKIP countermeasures (see 8.3.2.4) if less than 60 * seconds have passed since the most recent previous MIC failure. */ if (ic->ic_tkip_micfail == 0 || ticks >= ic->ic_tkip_micfail + 60 * hz) { ic->ic_tkip_micfail = ticks; return; } ic->ic_tkip_micfail = ticks; switch (ic->ic_opmode) { #ifndef IEEE80211_STA_ONLY case IEEE80211_M_HOSTAP: /* refuse new TKIP associations for the next 60 seconds */ ic->ic_flags |= IEEE80211_F_COUNTERM; /* deauthenticate all currently associated STAs using TKIP */ ieee80211_iterate_nodes(ic, ieee80211_tkip_deauth, ic); break; #endif case IEEE80211_M_STA: /* deauthenticate from the AP.. */ IEEE80211_SEND_MGMT(ic, ic->ic_bss, IEEE80211_FC0_SUBTYPE_DEAUTH, IEEE80211_REASON_MIC_FAILURE); /* ..and find another one */ (void)ieee80211_new_state(ic, IEEE80211_S_SCAN, -1); break; default: break; } } /*********************************************************************** Contents: Generate IEEE 802.11 per-frame RC4 key hash test vectors Date: April 19, 2002 Notes: This code is written for pedagogical purposes, NOT for performance. ************************************************************************/ /* macros for extraction/creation of byte/u16b values */ #define RotR1(v16) ((((v16) >> 1) & 0x7FFF) ^ (((v16) & 1) << 15)) #define Lo8(v16) ((byte)( (v16) & 0x00FF)) #define Hi8(v16) ((byte)(((v16) >> 8) & 0x00FF)) #define Lo16(v32) ((u16b)( (v32) & 0xFFFF)) #define Hi16(v32) ((u16b)(((v32) >>16) & 0xFFFF)) #define Mk16(hi,lo) ((lo) ^ (((u16b)(hi)) << 8)) /* select the Nth 16-bit word of the Temporal Key byte array TK[] */ #define TK16(N) Mk16(TK[2 * (N) + 1], TK[2 * (N)]) /* S-box lookup: 16 bits --> 16 bits */ #define _S_(v16) (Sbox[Lo8(v16)] ^ swap16(Sbox[Hi8(v16)])) /* fixed algorithm "parameters" */ #define PHASE1_LOOP_CNT 8 /* this needs to be "big enough" */ #define TA_SIZE 6 /* 48-bit transmitter address */ #define TK_SIZE 16 /* 128-bit Temporal Key */ #define P1K_SIZE 10 /* 80-bit Phase1 key */ #define RC4_KEY_SIZE 16 /* 128-bit RC4KEY (104 bits unknown) */ /* 2-byte by 2-byte subset of the full AES S-box table */ static const u16b Sbox[256]= /* Sbox for hash */ { 0xC6A5, 0xF884, 0xEE99, 0xF68D, 0xFF0D, 0xD6BD, 0xDEB1, 0x9154, 0x6050, 0x0203, 0xCEA9, 0x567D, 0xE719, 0xB562, 0x4DE6, 0xEC9A, 0x8F45, 0x1F9D, 0x8940, 0xFA87, 0xEF15, 0xB2EB, 0x8EC9, 0xFB0B, 0x41EC, 0xB367, 0x5FFD, 0x45EA, 0x23BF, 0x53F7, 0xE496, 0x9B5B, 0x75C2, 0xE11C, 0x3DAE, 0x4C6A, 0x6C5A, 0x7E41, 0xF502, 0x834F, 0x685C, 0x51F4, 0xD134, 0xF908, 0xE293, 0xAB73, 0x6253, 0x2A3F, 0x080C, 0x9552, 0x4665, 0x9D5E, 0x3028, 0x37A1, 0x0A0F, 0x2FB5, 0x0E09, 0x2436, 0x1B9B, 0xDF3D, 0xCD26, 0x4E69, 0x7FCD, 0xEA9F, 0x121B, 0x1D9E, 0x5874, 0x342E, 0x362D, 0xDCB2, 0xB4EE, 0x5BFB, 0xA4F6, 0x764D, 0xB761, 0x7DCE, 0x527B, 0xDD3E, 0x5E71, 0x1397, 0xA6F5, 0xB968, 0x0000, 0xC12C, 0x4060, 0xE31F, 0x79C8, 0xB6ED, 0xD4BE, 0x8D46, 0x67D9, 0x724B, 0x94DE, 0x98D4, 0xB0E8, 0x854A, 0xBB6B, 0xC52A, 0x4FE5, 0xED16, 0x86C5, 0x9AD7, 0x6655, 0x1194, 0x8ACF, 0xE910, 0x0406, 0xFE81, 0xA0F0, 0x7844, 0x25BA, 0x4BE3, 0xA2F3, 0x5DFE, 0x80C0, 0x058A, 0x3FAD, 0x21BC, 0x7048, 0xF104, 0x63DF, 0x77C1, 0xAF75, 0x4263, 0x2030, 0xE51A, 0xFD0E, 0xBF6D, 0x814C, 0x1814, 0x2635, 0xC32F, 0xBEE1, 0x35A2, 0x88CC, 0x2E39, 0x9357, 0x55F2, 0xFC82, 0x7A47, 0xC8AC, 0xBAE7, 0x322B, 0xE695, 0xC0A0, 0x1998, 0x9ED1, 0xA37F, 0x4466, 0x547E, 0x3BAB, 0x0B83, 0x8CCA, 0xC729, 0x6BD3, 0x283C, 0xA779, 0xBCE2, 0x161D, 0xAD76, 0xDB3B, 0x6456, 0x744E, 0x141E, 0x92DB, 0x0C0A, 0x486C, 0xB8E4, 0x9F5D, 0xBD6E, 0x43EF, 0xC4A6, 0x39A8, 0x31A4, 0xD337, 0xF28B, 0xD532, 0x8B43, 0x6E59, 0xDAB7, 0x018C, 0xB164, 0x9CD2, 0x49E0, 0xD8B4, 0xACFA, 0xF307, 0xCF25, 0xCAAF, 0xF48E, 0x47E9, 0x1018, 0x6FD5, 0xF088, 0x4A6F, 0x5C72, 0x3824, 0x57F1, 0x73C7, 0x9751, 0xCB23, 0xA17C, 0xE89C, 0x3E21, 0x96DD, 0x61DC, 0x0D86, 0x0F85, 0xE090, 0x7C42, 0x71C4, 0xCCAA, 0x90D8, 0x0605, 0xF701, 0x1C12, 0xC2A3, 0x6A5F, 0xAEF9, 0x69D0, 0x1791, 0x9958, 0x3A27, 0x27B9, 0xD938, 0xEB13, 0x2BB3, 0x2233, 0xD2BB, 0xA970, 0x0789, 0x33A7, 0x2DB6, 0x3C22, 0x1592, 0xC920, 0x8749, 0xAAFF, 0x5078, 0xA57A, 0x038F, 0x59F8, 0x0980, 0x1A17, 0x65DA, 0xD731, 0x84C6, 0xD0B8, 0x82C3, 0x29B0, 0x5A77, 0x1E11, 0x7BCB, 0xA8FC, 0x6DD6, 0x2C3A }; /* ********************************************************************** * Routine: Phase 1 -- generate P1K, given TA, TK, IV32 * * Inputs: * TK[] = Temporal Key [128 bits] * TA[] = transmitter's MAC address [ 48 bits] * IV32 = upper 32 bits of IV [ 32 bits] * Output: * P1K[] = Phase 1 key [ 80 bits] * * Note: * This function only needs to be called every 2**16 frames, * although in theory it could be called every frame. * ********************************************************************** */ static void Phase1(u16b *P1K, const byte *TK, const byte *TA, u32b IV32) { int i; /* Initialize the 80 bits of P1K[] from IV32 and TA[0..5] */ P1K[0] = Lo16(IV32); P1K[1] = Hi16(IV32); P1K[2] = Mk16(TA[1], TA[0]); /* use TA[] as little-endian */ P1K[3] = Mk16(TA[3], TA[2]); P1K[4] = Mk16(TA[5], TA[4]); /* Now compute an unbalanced Feistel cipher with 80-bit block */ /* size on the 80-bit block P1K[], using the 128-bit key TK[] */ for (i = 0; i < PHASE1_LOOP_CNT; i++) { /* Each add operation here is mod 2**16 */ P1K[0] += _S_(P1K[4] ^ TK16((i & 1) + 0)); P1K[1] += _S_(P1K[0] ^ TK16((i & 1) + 2)); P1K[2] += _S_(P1K[1] ^ TK16((i & 1) + 4)); P1K[3] += _S_(P1K[2] ^ TK16((i & 1) + 6)); P1K[4] += _S_(P1K[3] ^ TK16((i & 1) + 0)); P1K[4] += i; /* avoid "slide attacks" */ } } /* ********************************************************************** * Routine: Phase 2 -- generate RC4KEY, given TK, P1K, IV16 * * Inputs: * TK[] = Temporal Key [128 bits] * P1K[] = Phase 1 output key [ 80 bits] * IV16 = low 16 bits of IV counter [ 16 bits] * Output: * RC4KEY[] = the key used to encrypt the frame [128 bits] * * Note: * The value {TA,IV32,IV16} for Phase1/Phase2 must be unique * across all frames using the same key TK value. Then, for a * given value of TK[], this TKIP48 construction guarantees that * the final RC4KEY value is unique across all frames. * ********************************************************************** */ static void Phase2(byte *RC4KEY, const byte *TK, const u16b *P1K, u16b IV16) { u16b *PPK; /* temporary key for mixing */ int i; /* * Suggested implementation optimization: if PPK[] is "overlaid" * appropriately on RC4KEY[], there is no need for the final for * loop that copies the PPK[] result into RC4KEY[]. */ PPK = (u16b *)&RC4KEY[4]; /* all adds in the PPK[] equations below are mod 2**16 */ for (i = 0; i < 5; i++) PPK[i] = P1K[i]; /* first, copy P1K to PPK */ PPK[5] = P1K[4] + IV16; /* next, add in IV16 */ /* Bijective non-linear mixing of the 96 bits of PPK[0..5] */ PPK[0] += _S_(PPK[5] ^ TK16(0)); /* Mix key in each "round" */ PPK[1] += _S_(PPK[0] ^ TK16(1)); PPK[2] += _S_(PPK[1] ^ TK16(2)); PPK[3] += _S_(PPK[2] ^ TK16(3)); PPK[4] += _S_(PPK[3] ^ TK16(4)); PPK[5] += _S_(PPK[4] ^ TK16(5)); /* Total # S-box lookups == 6 */ /* Final sweep: bijective, linear. Rotates kill LSB correlations */ PPK[0] += RotR1(PPK[5] ^ TK16(6)); PPK[1] += RotR1(PPK[0] ^ TK16(7)); /* Use all of TK[] in Phase2 */ PPK[2] += RotR1(PPK[1]); PPK[3] += RotR1(PPK[2]); PPK[4] += RotR1(PPK[3]); PPK[5] += RotR1(PPK[4]); /* At this point, for a given key TK[0..15], the 96-bit output */ /* value PPK[0..5] is guaranteed to be unique, as a function */ /* of the 96-bit "input" value {TA,IV32,IV16}. That is, P1K */ /* is now a keyed permutation of {TA,IV32,IV16}. */ /* Set RC4KEY[0..3], which includes cleartext portion of RC4 key */ RC4KEY[0] = Hi8(IV16); /* RC4KEY[0..2] is the WEP IV */ RC4KEY[1] =(Hi8(IV16) | 0x20) & 0x7F; /* Help avoid FMS weak keys */ RC4KEY[2] = Lo8(IV16); RC4KEY[3] = Lo8((PPK[5] ^ TK16(0)) >> 1); #if BYTE_ORDER == BIG_ENDIAN /* Copy 96 bits of PPK[0..5] to RC4KEY[4..15] (little-endian) */ for (i = 0; i < 6; i++) PPK[i] = swap16(PPK[i]); #endif }