diff --git a/include/osmocom/gsm/Makefile.am b/include/osmocom/gsm/Makefile.am index 8685fc9a6..a39d2d04e 100644 --- a/include/osmocom/gsm/Makefile.am +++ b/include/osmocom/gsm/Makefile.am @@ -1,4 +1,4 @@ -osmogsm_HEADERS = comp128.h gsm0808.h gsm48_ie.h mncc.h rxlev_stat.h \ +osmogsm_HEADERS = a5.h comp128.h gsm0808.h gsm48_ie.h mncc.h rxlev_stat.h \ gsm0480.h gsm48.h gsm_utils.h rsl.h tlv.h SUBDIRS = protocol diff --git a/include/osmocom/gsm/a5.h b/include/osmocom/gsm/a5.h new file mode 100644 index 000000000..2c630e5f1 --- /dev/null +++ b/include/osmocom/gsm/a5.h @@ -0,0 +1,49 @@ +/* + * a5.h + * + * Copyright (C) 2011 Sylvain Munaut + * + * All Rights Reserved + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#ifndef __OSMO_A5_H__ +#define __OSMO_A5_H__ + +#include + +#include + +static inline uint32_t +osmo_a5_fn_count(uint32_t fn) +{ + int t1 = fn / (26 * 51); + int t2 = fn % 26; + int t3 = fn % 51; + return (t1 << 11) | (t3 << 5) | t2; +} + + /* Notes: + * - key must be 8 bytes long (or NULL for A5/0) + * - the dl and ul pointer must be either NULL or 114 bits long + * - fn is the _real_ GSM frame number. + * (converted internally to fn_count) + */ +void osmo_a5(int n, uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul); +void osmo_a5_1(uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul); +void osmo_a5_2(uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul); + +#endif /* __OSMO_A5_H__ */ diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am index a8c2e5692..57eb5cadf 100644 --- a/src/gsm/Makefile.am +++ b/src/gsm/Makefile.am @@ -7,7 +7,7 @@ AM_CFLAGS = -fPIC -Wall lib_LTLIBRARIES = libosmogsm.la -libosmogsm_la_SOURCES = rxlev_stat.c tlv_parser.c comp128.c gsm_utils.c \ +libosmogsm_la_SOURCES = a5.c rxlev_stat.c tlv_parser.c comp128.c gsm_utils.c \ rsl.c gsm48.c gsm48_ie.c gsm0808.c \ gprs_cipher_core.c gsm0480.c libosmogsm_la_LIBADD = $(top_builddir)/src/libosmocore.la diff --git a/src/gsm/a5.c b/src/gsm/a5.c new file mode 100644 index 000000000..d3f2b2c30 --- /dev/null +++ b/src/gsm/a5.c @@ -0,0 +1,311 @@ +/* + * a5.c + * + * Full reimplementation of A5/1,2 (split and threadsafe) + * + * The logic behind the algorithm is taken from "A pedagogical implementation + * of the GSM A5/1 and A5/2 "voice privacy" encryption algorithms." by + * Marc Briceno, Ian Goldberg, and David Wagner. + * + * Copyright (C) 2011 Sylvain Munaut + * + * All Rights Reserved + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include + +#include + +void +osmo_a5(int n, uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul) +{ + switch (n) + { + case 0: + if (dl) + memset(dl, 0x00, 114); + if (ul) + memset(ul, 0x00, 114); + break; + + case 1: + osmo_a5_1(key, fn, dl, ul); + break; + + case 2: + osmo_a5_2(key, fn, dl, ul); + break; + + default: + /* a5/[3..7] not supported here/yet */ + break; + } +} + + +/* ------------------------------------------------------------------------ */ +/* A5/1&2 common stuff */ +/* ------------------------------------------------------------------------ */ + +#define A5_R1_LEN 19 +#define A5_R2_LEN 22 +#define A5_R3_LEN 23 +#define A5_R4_LEN 17 /* A5/2 only */ + +#define A5_R1_MASK ((1<> 16; + x ^= x >> 8; + x ^= x >> 4; + x ^= x >> 2; + x ^= x >> 1; + return x & 1; +} + +static inline uint32_t +_a5_12_majority(uint32_t v1, uint32_t v2, uint32_t v3) +{ + return (!!v1 + !!v2 + !!v3) >= 2; +} + +static inline uint32_t +_a5_12_clock(uint32_t r, uint32_t mask, uint32_t taps) +{ + return ((r << 1) & mask) | _a5_12_parity(r & taps); +} + + +/* ------------------------------------------------------------------------ */ +/* A5/1 */ +/* ------------------------------------------------------------------------ */ + +#define A51_R1_CLKBIT 0x000100 +#define A51_R2_CLKBIT 0x000400 +#define A51_R3_CLKBIT 0x000400 + +static inline void +_a5_1_clock(uint32_t r[], int force) +{ + int cb[3], maj; + + cb[0] = !!(r[0] & A51_R1_CLKBIT); + cb[1] = !!(r[1] & A51_R2_CLKBIT); + cb[2] = !!(r[2] & A51_R3_CLKBIT); + + maj = _a5_12_majority(cb[0], cb[1], cb[2]); + + if (force || (maj == cb[0])) + r[0] = _a5_12_clock(r[0], A5_R1_MASK, A5_R1_TAPS); + + if (force || (maj == cb[1])) + r[1] = _a5_12_clock(r[1], A5_R2_MASK, A5_R2_TAPS); + + if (force || (maj == cb[2])) + r[2] = _a5_12_clock(r[2], A5_R3_MASK, A5_R3_TAPS); +} + +static inline uint8_t +_a5_1_get_output(uint32_t r[]) +{ + return (r[0] >> (A5_R1_LEN-1)) ^ + (r[1] >> (A5_R2_LEN-1)) ^ + (r[2] >> (A5_R3_LEN-1)); +} + +void +osmo_a5_1(uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul) +{ + uint32_t r[3] = {0, 0, 0}; + uint32_t fn_count; + uint32_t b; + int i; + + /* Key load */ + for (i=0; i<64; i++) + { + b = ( key[7 - (i>>3)] >> (i&7) ) & 1; + + _a5_1_clock(r, 1); + + r[0] ^= b; + r[1] ^= b; + r[2] ^= b; + } + + /* Frame count load */ + fn_count = osmo_a5_fn_count(fn); + + for (i=0; i<22; i++) + { + b = (fn_count >> i) & 1; + + _a5_1_clock(r, 1); + + r[0] ^= b; + r[1] ^= b; + r[2] ^= b; + } + + /* Mix */ + for (i=0; i<100; i++) + { + _a5_1_clock(r, 0); + } + + /* Output */ + for (i=0; i<114; i++) { + _a5_1_clock(r, 0); + if (dl) + dl[i] = _a5_1_get_output(r); + } + + for (i=0; i<114; i++) { + _a5_1_clock(r, 0); + if (ul) + ul[i] = _a5_1_get_output(r); + } +} + + +/* ------------------------------------------------------------------------ */ +/* A5/2 */ +/* ------------------------------------------------------------------------ */ + +#define A52_R4_CLKBIT0 0x000400 +#define A52_R4_CLKBIT1 0x000008 +#define A52_R4_CLKBIT2 0x000080 + +static inline void +_a5_2_clock(uint32_t r[], int force) +{ + int cb[3], maj; + + cb[0] = !!(r[3] & A52_R4_CLKBIT0); + cb[1] = !!(r[3] & A52_R4_CLKBIT1); + cb[2] = !!(r[3] & A52_R4_CLKBIT2); + + maj = (cb[0] + cb[1] + cb[2]) >= 2; + + if (force || (maj == cb[0])) + r[0] = _a5_12_clock(r[0], A5_R1_MASK, A5_R1_TAPS); + + if (force || (maj == cb[1])) + r[1] = _a5_12_clock(r[1], A5_R2_MASK, A5_R2_TAPS); + + if (force || (maj == cb[2])) + r[2] = _a5_12_clock(r[2], A5_R3_MASK, A5_R3_TAPS); + + r[3] = _a5_12_clock(r[3], A5_R4_MASK, A5_R4_TAPS); +} + +static inline uint8_t +_a5_2_get_output(uint32_t r[], uint8_t *db) +{ + uint8_t cb, tb; + + tb = (r[0] >> (A5_R1_LEN-1)) ^ + (r[1] >> (A5_R2_LEN-1)) ^ + (r[2] >> (A5_R3_LEN-1)); + + cb = *db; + + *db = ( tb ^ + _a5_12_majority( r[0] & 0x08000, ~r[0] & 0x04000, r[0] & 0x1000) ^ + _a5_12_majority(~r[1] & 0x10000, r[1] & 0x02000, r[1] & 0x0200) ^ + _a5_12_majority( r[2] & 0x40000, r[2] & 0x10000, ~r[2] & 0x2000) + ); + + return cb; +} + +void +osmo_a5_2(uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul) +{ + uint32_t r[4] = {0, 0, 0, 0}; + uint32_t fn_count; + uint32_t b; + uint8_t db = 0, o; + int i; + + /* Key load */ + for (i=0; i<64; i++) + { + b = ( key[7 - (i>>3)] >> (i&7) ) & 1; + + _a5_2_clock(r, 1); + + r[0] ^= b; + r[1] ^= b; + r[2] ^= b; + r[3] ^= b; + } + + /* Frame count load */ + fn_count = osmo_a5_fn_count(fn); + + for (i=0; i<22; i++) + { + b = (fn_count >> i) & 1; + + _a5_2_clock(r, 1); + + r[0] ^= b; + r[1] ^= b; + r[2] ^= b; + r[3] ^= b; + } + + r[0] |= 1 << 15; + r[1] |= 1 << 16; + r[2] |= 1 << 18; + r[3] |= 1 << 10; + + /* Mix */ + for (i=0; i<100; i++) + { + _a5_2_clock(r, 0); + } + + _a5_2_get_output(r, &db); + + + /* Output */ + for (i=0; i<114; i++) { + _a5_2_clock(r, 0); + o = _a5_2_get_output(r, &db); + if (dl) + dl[i] = o; + } + + for (i=0; i<114; i++) { + _a5_2_clock(r, 0); + o = _a5_2_get_output(r, &db); + if (ul) + ul[i] = o; + } +}