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Diffstat (limited to 'openbsc/src/msc/a3a8.c')
| -rw-r--r-- | openbsc/src/msc/a3a8.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/openbsc/src/msc/a3a8.c b/openbsc/src/msc/a3a8.c new file mode 100644 index 000000000..04470ba18 --- /dev/null +++ b/openbsc/src/msc/a3a8.c @@ -0,0 +1,269 @@ +/* An implementation of the GSM A3A8 algorithm. (Specifically, COMP128.) + */ + +/* Copyright 1998, Marc Briceno, Ian Goldberg, and David Wagner. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * * Neither the name of the authors nor the names of the contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/* + * Coded in C merely because C is a much more precise, concise form of + * expression for these purposes. See Judge Patel if you have any problems + * with this... + * Of course, it's only authentication, so it should be exportable for the + * usual boring reasons. + */ + +typedef unsigned char Byte; + +#include <stdio.h> +/* #define TEST */ + +/* + * rand[0..15]: the challenge from the base station + * key[0..15]: the SIM's A3/A8 long-term key Ki + * simoutput[0..11]: what you'd get back if you fed rand and key to a real + * SIM. + * + * The GSM spec states that simoutput[0..3] is SRES, + * and simoutput[4..11] is Kc (the A5 session key). + * (See GSM 11.11, Section 8.16. See also the leaked document + * referenced below.) + * Note that Kc is bits 74..127 of the COMP128 output, followed by 10 + * zeros. + * In other words, A5 is keyed with only 54 bits of entropy. This + * represents a deliberate weakening of the key used for voice privacy + * by a factor of over 1000. + * + * Verified with a Pacific Bell Schlumberger SIM. Your mileage may vary. + * + * Marc Briceno <marc@scard.org>, Ian Goldberg <iang@cs.berkeley.edu>, + * and David Wagner <daw@cs.berkeley.edu> + */ + +void A3A8(/* in */ Byte rand[16], /* in */ Byte key[16], + /* out */ Byte simoutput[12]); + +/* The compression tables. */ +static const Byte table_0[512] = { + 102,177,186,162, 2,156,112, 75, 55, 25, 8, 12,251,193,246,188, + 109,213,151, 53, 42, 79,191,115,233,242,164,223,209,148,108,161, + 252, 37,244, 47, 64,211, 6,237,185,160,139,113, 76,138, 59, 70, + 67, 26, 13,157, 63,179,221, 30,214, 36,166, 69,152,124,207,116, + 247,194, 41, 84, 71, 1, 49, 14, 95, 35,169, 21, 96, 78,215,225, + 182,243, 28, 92,201,118, 4, 74,248,128, 17, 11,146,132,245, 48, + 149, 90,120, 39, 87,230,106,232,175, 19,126,190,202,141,137,176, + 250, 27,101, 40,219,227, 58, 20, 51,178, 98,216,140, 22, 32,121, + 61,103,203, 72, 29,110, 85,212,180,204,150,183, 15, 66,172,196, + 56,197,158, 0,100, 45,153, 7,144,222,163,167, 60,135,210,231, + 174,165, 38,249,224, 34,220,229,217,208,241, 68,206,189,125,255, + 239, 54,168, 89,123,122, 73,145,117,234,143, 99,129,200,192, 82, + 104,170,136,235, 93, 81,205,173,236, 94,105, 52, 46,228,198, 5, + 57,254, 97,155,142,133,199,171,187, 50, 65,181,127,107,147,226, + 184,218,131, 33, 77, 86, 31, 44, 88, 62,238, 18, 24, 43,154, 23, + 80,159,134,111, 9,114, 3, 91, 16,130, 83, 10,195,240,253,119, + 177,102,162,186,156, 2, 75,112, 25, 55, 12, 8,193,251,188,246, + 213,109, 53,151, 79, 42,115,191,242,233,223,164,148,209,161,108, + 37,252, 47,244,211, 64,237, 6,160,185,113,139,138, 76, 70, 59, + 26, 67,157, 13,179, 63, 30,221, 36,214, 69,166,124,152,116,207, + 194,247, 84, 41, 1, 71, 14, 49, 35, 95, 21,169, 78, 96,225,215, + 243,182, 92, 28,118,201, 74, 4,128,248, 11, 17,132,146, 48,245, + 90,149, 39,120,230, 87,232,106, 19,175,190,126,141,202,176,137, + 27,250, 40,101,227,219, 20, 58,178, 51,216, 98, 22,140,121, 32, + 103, 61, 72,203,110, 29,212, 85,204,180,183,150, 66, 15,196,172, + 197, 56, 0,158, 45,100, 7,153,222,144,167,163,135, 60,231,210, + 165,174,249, 38, 34,224,229,220,208,217, 68,241,189,206,255,125, + 54,239, 89,168,122,123,145, 73,234,117, 99,143,200,129, 82,192, + 170,104,235,136, 81, 93,173,205, 94,236, 52,105,228, 46, 5,198, + 254, 57,155, 97,133,142,171,199, 50,187,181, 65,107,127,226,147, + 218,184, 33,131, 86, 77, 44, 31, 62, 88, 18,238, 43, 24, 23,154, + 159, 80,111,134,114, 9, 91, 3,130, 16, 10, 83,240,195,119,253 + }, table_1[256] = { + 19, 11, 80,114, 43, 1, 69, 94, 39, 18,127,117, 97, 3, 85, 43, + 27,124, 70, 83, 47, 71, 63, 10, 47, 89, 79, 4, 14, 59, 11, 5, + 35,107,103, 68, 21, 86, 36, 91, 85,126, 32, 50,109, 94,120, 6, + 53, 79, 28, 45, 99, 95, 41, 34, 88, 68, 93, 55,110,125,105, 20, + 90, 80, 76, 96, 23, 60, 89, 64,121, 56, 14, 74,101, 8, 19, 78, + 76, 66,104, 46,111, 50, 32, 3, 39, 0, 58, 25, 92, 22, 18, 51, + 57, 65,119,116, 22,109, 7, 86, 59, 93, 62,110, 78, 99, 77, 67, + 12,113, 87, 98,102, 5, 88, 33, 38, 56, 23, 8, 75, 45, 13, 75, + 95, 63, 28, 49,123,120, 20,112, 44, 30, 15, 98,106, 2,103, 29, + 82,107, 42,124, 24, 30, 41, 16,108,100,117, 40, 73, 40, 7,114, + 82,115, 36,112, 12,102,100, 84, 92, 48, 72, 97, 9, 54, 55, 74, + 113,123, 17, 26, 53, 58, 4, 9, 69,122, 21,118, 42, 60, 27, 73, + 118,125, 34, 15, 65,115, 84, 64, 62, 81, 70, 1, 24,111,121, 83, + 104, 81, 49,127, 48,105, 31, 10, 6, 91, 87, 37, 16, 54,116,126, + 31, 38, 13, 0, 72,106, 77, 61, 26, 67, 46, 29, 96, 37, 61, 52, + 101, 17, 44,108, 71, 52, 66, 57, 33, 51, 25, 90, 2,119,122, 35 + }, table_2[128] = { + 52, 50, 44, 6, 21, 49, 41, 59, 39, 51, 25, 32, 51, 47, 52, 43, + 37, 4, 40, 34, 61, 12, 28, 4, 58, 23, 8, 15, 12, 22, 9, 18, + 55, 10, 33, 35, 50, 1, 43, 3, 57, 13, 62, 14, 7, 42, 44, 59, + 62, 57, 27, 6, 8, 31, 26, 54, 41, 22, 45, 20, 39, 3, 16, 56, + 48, 2, 21, 28, 36, 42, 60, 33, 34, 18, 0, 11, 24, 10, 17, 61, + 29, 14, 45, 26, 55, 46, 11, 17, 54, 46, 9, 24, 30, 60, 32, 0, + 20, 38, 2, 30, 58, 35, 1, 16, 56, 40, 23, 48, 13, 19, 19, 27, + 31, 53, 47, 38, 63, 15, 49, 5, 37, 53, 25, 36, 63, 29, 5, 7 + }, table_3[64] = { + 1, 5, 29, 6, 25, 1, 18, 23, 17, 19, 0, 9, 24, 25, 6, 31, + 28, 20, 24, 30, 4, 27, 3, 13, 15, 16, 14, 18, 4, 3, 8, 9, + 20, 0, 12, 26, 21, 8, 28, 2, 29, 2, 15, 7, 11, 22, 14, 10, + 17, 21, 12, 30, 26, 27, 16, 31, 11, 7, 13, 23, 10, 5, 22, 19 + }, table_4[32] = { + 15, 12, 10, 4, 1, 14, 11, 7, 5, 0, 14, 7, 1, 2, 13, 8, + 10, 3, 4, 9, 6, 0, 3, 2, 5, 6, 8, 9, 11, 13, 15, 12 + }, *table[5] = { table_0, table_1, table_2, table_3, table_4 }; + +/* + * This code derived from a leaked document from the GSM standards. + * Some missing pieces were filled in by reverse-engineering a working SIM. + * We have verified that this is the correct COMP128 algorithm. + * + * The first page of the document identifies it as + * _Technical Information: GSM System Security Study_. + * 10-1617-01, 10th June 1988. + * The bottom of the title page is marked + * Racal Research Ltd. + * Worton Drive, Worton Grange Industrial Estate, + * Reading, Berks. RG2 0SB, England. + * Telephone: Reading (0734) 868601 Telex: 847152 + * The relevant bits are in Part I, Section 20 (pages 66--67). Enjoy! + * + * Note: There are three typos in the spec (discovered by + * reverse-engineering). + * First, "z = (2 * x[n] + x[n]) mod 2^(9-j)" should clearly read + * "z = (2 * x[m] + x[n]) mod 2^(9-j)". + * Second, the "k" loop in the "Form bits from bytes" section is severely + * botched: the k index should run only from 0 to 3, and clearly the range + * on "the (8-k)th bit of byte j" is also off (should be 0..7, not 1..8, + * to be consistent with the subsequent section). + * Third, SRES is taken from the first 8 nibbles of x[], not the last 8 as + * claimed in the document. (And the document doesn't specify how Kc is + * derived, but that was also easily discovered with reverse engineering.) + * All of these typos have been corrected in the following code. + */ + +void A3A8(/* in */ Byte rand[16], /* in */ Byte key[16], + /* out */ Byte simoutput[12]) +{ + Byte x[32], bit[128]; + int i, j, k, l, m, n, y, z, next_bit; + + /* ( Load RAND into last 16 bytes of input ) */ + for (i=16; i<32; i++) + x[i] = rand[i-16]; + + /* ( Loop eight times ) */ + for (i=1; i<9; i++) { + /* ( Load key into first 16 bytes of input ) */ + for (j=0; j<16; j++) + x[j] = key[j]; + /* ( Perform substitutions ) */ + for (j=0; j<5; j++) + for (k=0; k<(1<<j); k++) + for (l=0; l<(1<<(4-j)); l++) { + m = l + k*(1<<(5-j)); + n = m + (1<<(4-j)); + y = (x[m]+2*x[n]) % (1<<(9-j)); + z = (2*x[m]+x[n]) % (1<<(9-j)); + x[m] = table[j][y]; + x[n] = table[j][z]; + } + /* ( Form bits from bytes ) */ + for (j=0; j<32; j++) + for (k=0; k<4; k++) + bit[4*j+k] = (x[j]>>(3-k)) & 1; + /* ( Permutation but not on the last loop ) */ + if (i < 8) + for (j=0; j<16; j++) { + x[j+16] = 0; + for (k=0; k<8; k++) { + next_bit = ((8*j + k)*17) % 128; + x[j+16] |= bit[next_bit] << (7-k); + } + } + } + + /* + * ( At this stage the vector x[] consists of 32 nibbles. + * The first 8 of these are taken as the output SRES. ) + */ + + /* The remainder of the code is not given explicitly in the + * standard, but was derived by reverse-engineering. + */ + + for (i=0; i<4; i++) + simoutput[i] = (x[2*i]<<4) | x[2*i+1]; + for (i=0; i<6; i++) + simoutput[4+i] = (x[2*i+18]<<6) | (x[2*i+18+1]<<2) + | (x[2*i+18+2]>>2); + simoutput[4+6] = (x[2*6+18]<<6) | (x[2*6+18+1]<<2); + simoutput[4+7] = 0; +} + + +#ifdef TEST +int hextoint(char x) +{ + x = toupper(x); + if (x >= 'A' && x <= 'F') + return x-'A'+10; + else if (x >= '0' && x <= '9') + return x-'0'; + fprintf(stderr, "bad input.\n"); + exit(1); +} + +int main(int argc, char **argv) +{ + Byte key[16], rand[16], simoutput[12]; + int i; + + if (argc != 3 || strlen(argv[1]) != 34 || strlen(argv[2]) != 34 + || strncmp(argv[1], "0x", 2) != 0 + || strncmp(argv[2], "0x", 2) != 0) { + fprintf(stderr, "Usage: %s 0x<key> 0x<rand>\n", argv[0]); + exit(1); + } + + for (i=0; i<16; i++) + key[i] = (hextoint(argv[1][2*i+2])<<4) + | hextoint(argv[1][2*i+3]); + for (i=0; i<16; i++) + rand[i] = (hextoint(argv[2][2*i+2])<<4) + | hextoint(argv[2][2*i+3]); + A3A8(rand, key, simoutput); + printf("simoutput: "); + for (i=0; i<12; i++) + printf("%02X", simoutput[i]); + printf("\n"); + return 0; +} +#endif + |