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Annotation of src/usr.bin/ssh/mpaux.c, Revision 1.1

1.1     ! deraadt     1: /*
        !             2:
        !             3: mpaux.c
        !             4:
        !             5: Author: Tatu Ylonen <ylo@cs.hut.fi>
        !             6:
        !             7: Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
        !             8:                    All rights reserved
        !             9:
        !            10: Created: Sun Jul 16 04:29:30 1995 ylo
        !            11:
        !            12: This file contains various auxiliary functions related to multiple
        !            13: precision integers.
        !            14:
        !            15: */
        !            16:
        !            17: #include "includes.h"
        !            18: RCSID("$Id: mpaux.c,v 1.3 1999/05/04 11:58:51 bg Exp $");
        !            19:
        !            20: #include <gmp.h>
        !            21: #include "getput.h"
        !            22: #include "xmalloc.h"
        !            23: #include "ssh_md5.h"
        !            24:
        !            25: /* Converts a multiple-precision integer into bytes to be stored in the buffer.
        !            26:    The buffer will contain the value of the integer, msb first. */
        !            27:
        !            28: void mp_linearize_msb_first(unsigned char *buf, unsigned int len,
        !            29:                            MP_INT *value)
        !            30: {
        !            31:   unsigned int i;
        !            32:   MP_INT aux;
        !            33:   mpz_init_set(&aux, value);
        !            34:   for (i = len; i >= 4; i -= 4)
        !            35:     {
        !            36:       unsigned int limb = mpz_get_ui(&aux);
        !            37:       PUT_32BIT(buf + i - 4, limb);
        !            38:       mpz_div_2exp(&aux, &aux, 32);
        !            39:     }
        !            40:   for (; i > 0; i--)
        !            41:     {
        !            42:       buf[i - 1] = mpz_get_ui(&aux);
        !            43:       mpz_div_2exp(&aux, &aux, 8);
        !            44:     }
        !            45:   mpz_clear(&aux);
        !            46: }
        !            47:
        !            48: /* Extract a multiple-precision integer from buffer.  The value is stored
        !            49:    in the buffer msb first. */
        !            50:
        !            51: void mp_unlinearize_msb_first(MP_INT *value, const unsigned char *buf,
        !            52:                              unsigned int len)
        !            53: {
        !            54:   unsigned int i;
        !            55:   mpz_set_ui(value, 0);
        !            56:   for (i = 0; i + 4 <= len; i += 4)
        !            57:     {
        !            58:       unsigned int limb = GET_32BIT(buf + i);
        !            59:       mpz_mul_2exp(value, value, 32);
        !            60:       mpz_add_ui(value, value, limb);
        !            61:     }
        !            62:   for (; i < len; i++)
        !            63:     {
        !            64:       mpz_mul_2exp(value, value, 8);
        !            65:       mpz_add_ui(value, value, buf[i]);
        !            66:     }
        !            67: }
        !            68:
        !            69: /* Computes a 16-byte session id in the global variable session_id.
        !            70:    The session id is computed by concatenating the linearized, msb
        !            71:    first representations of host_key_n, session_key_n, and the cookie. */
        !            72:
        !            73: void compute_session_id(unsigned char session_id[16],
        !            74:                        unsigned char cookie[8],
        !            75:                        unsigned int host_key_bits,
        !            76:                        MP_INT *host_key_n,
        !            77:                        unsigned int session_key_bits,
        !            78:                        MP_INT *session_key_n)
        !            79: {
        !            80:   unsigned int bytes = (host_key_bits + 7) / 8 + (session_key_bits + 7) / 8 + 8;
        !            81:   unsigned char *buf = xmalloc(bytes);
        !            82:   struct MD5Context md;
        !            83:
        !            84:   mp_linearize_msb_first(buf, (host_key_bits + 7 ) / 8, host_key_n);
        !            85:   mp_linearize_msb_first(buf + (host_key_bits + 7 ) / 8,
        !            86:                         (session_key_bits + 7) / 8, session_key_n);
        !            87:   memcpy(buf + (host_key_bits + 7) / 8 + (session_key_bits + 7) / 8,
        !            88:         cookie, 8);
        !            89:   MD5Init(&md);
        !            90:   MD5Update(&md, buf, bytes);
        !            91:   MD5Final(session_id, &md);
        !            92:   xfree(buf);
        !            93: }