1 /* 2 * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 #include <stdio.h> 11 #include "internal/cryptlib.h" 12 #include "bn_local.h" 13 14 int BN_bn2mpi(const BIGNUM *a, unsigned char *d) 15 { 16 int bits; 17 int num = 0; 18 int ext = 0; 19 long l; 20 21 bits = BN_num_bits(a); 22 num = (bits + 7) / 8; 23 if (bits > 0) { 24 ext = ((bits & 0x07) == 0); 25 } 26 if (d == NULL) 27 return (num + 4 + ext); 28 29 l = num + ext; 30 d[0] = (unsigned char)(l >> 24) & 0xff; 31 d[1] = (unsigned char)(l >> 16) & 0xff; 32 d[2] = (unsigned char)(l >> 8) & 0xff; 33 d[3] = (unsigned char)(l) & 0xff; 34 if (ext) 35 d[4] = 0; 36 num = BN_bn2bin(a, &(d[4 + ext])); 37 if (a->neg) 38 d[4] |= 0x80; 39 return (num + 4 + ext); 40 } 41 42 BIGNUM *BN_mpi2bn(const unsigned char *d, int n, BIGNUM *ain) 43 { 44 long len; 45 int neg = 0; 46 BIGNUM *a = NULL; 47 48 if (n < 4 || (d[0] & 0x80) != 0) { 49 ERR_raise(ERR_LIB_BN, BN_R_INVALID_LENGTH); 50 return NULL; 51 } 52 len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) | (int) 53 d[3]; 54 if ((len + 4) != n) { 55 ERR_raise(ERR_LIB_BN, BN_R_ENCODING_ERROR); 56 return NULL; 57 } 58 59 if (ain == NULL) 60 a = BN_new(); 61 else 62 a = ain; 63 64 if (a == NULL) 65 return NULL; 66 67 if (len == 0) { 68 a->neg = 0; 69 a->top = 0; 70 return a; 71 } 72 d += 4; 73 if ((*d) & 0x80) 74 neg = 1; 75 if (BN_bin2bn(d, (int)len, a) == NULL) { 76 if (ain == NULL) 77 BN_free(a); 78 return NULL; 79 } 80 a->neg = neg; 81 if (neg) { 82 BN_clear_bit(a, BN_num_bits(a) - 1); 83 } 84 bn_check_top(a); 85 return a; 86 } 87