sha256.c

00001 /*********************************************************************
00002 * Filename:   sha256.c
00003 * Author:     Brad Conte (brad AT bradconte.com)
00004 * Copyright:
00005 * Disclaimer: This code is presented "as is" without any guarantees.
00006 * Details:    Implementation of the SHA-256 hashing algorithm.
00007               SHA-256 is one of the three algorithms in the SHA2
00008               specification. The others, SHA-384 and SHA-512, are not
00009               offered in this implementation.
00010               Algorithm specification can be found here:
00011                * http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf
00012               This implementation uses little endian byte order.
00013 *********************************************************************/
00014 
00015 /*************************** HEADER FILES ***************************/
00016 #include <stdlib.h>
00017 #include <string.h>
00018 #include "sha256.h"
00019 
00020 /****************************** MACROS ******************************/
00021 #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
00022 #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))
00023 
00024 #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
00025 #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
00026 #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
00027 #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
00028 #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
00029 #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))
00030 
00031 /**************************** VARIABLES *****************************/
00032 static const WORD k[64] = {
00033     0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
00034     0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
00035     0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
00036     0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
00037     0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
00038     0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
00039     0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
00040     0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
00041 };
00042 
00043 /*********************** FUNCTION DEFINITIONS ***********************/
00044 void sha256_transform(SHA256_CTX *ctx, const BYTE data[])
00045 {
00046     WORD a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
00047 
00048     for (i = 0, j = 0; i < 16; ++i, j += 4)
00049         m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
00050     for ( ; i < 64; ++i)
00051         m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
00052 
00053     a = ctx->state[0];
00054     b = ctx->state[1];
00055     c = ctx->state[2];
00056     d = ctx->state[3];
00057     e = ctx->state[4];
00058     f = ctx->state[5];
00059     g = ctx->state[6];
00060     h = ctx->state[7];
00061 
00062     for (i = 0; i < 64; ++i) {
00063         t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
00064         t2 = EP0(a) + MAJ(a,b,c);
00065         h = g;
00066         g = f;
00067         f = e;
00068         e = d + t1;
00069         d = c;
00070         c = b;
00071         b = a;
00072         a = t1 + t2;
00073     }
00074 
00075     ctx->state[0] += a;
00076     ctx->state[1] += b;
00077     ctx->state[2] += c;
00078     ctx->state[3] += d;
00079     ctx->state[4] += e;
00080     ctx->state[5] += f;
00081     ctx->state[6] += g;
00082     ctx->state[7] += h;
00083 }
00084 
00085 void sha256_init(SHA256_CTX *ctx)
00086 {
00087     ctx->datalen = 0;
00088     ctx->bitlen = 0;
00089     ctx->state[0] = 0x6a09e667;
00090     ctx->state[1] = 0xbb67ae85;
00091     ctx->state[2] = 0x3c6ef372;
00092     ctx->state[3] = 0xa54ff53a;
00093     ctx->state[4] = 0x510e527f;
00094     ctx->state[5] = 0x9b05688c;
00095     ctx->state[6] = 0x1f83d9ab;
00096     ctx->state[7] = 0x5be0cd19;
00097 }
00098 
00099 void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len)
00100 {
00101     WORD i;
00102 
00103     for (i = 0; i < len; ++i) {
00104         ctx->data[ctx->datalen] = data[i];
00105         ctx->datalen++;
00106         if (ctx->datalen == 64) {
00107             sha256_transform(ctx, ctx->data);
00108             ctx->bitlen += 512;
00109             ctx->datalen = 0;
00110         }
00111     }
00112 }
00113 
00114 void sha256_final(SHA256_CTX *ctx, BYTE hash[])
00115 {
00116     WORD i;
00117 
00118     i = ctx->datalen;
00119 
00120     // Pad whatever data is left in the buffer.
00121     if (ctx->datalen < 56) {
00122         ctx->data[i++] = 0x80;
00123         while (i < 56)
00124             ctx->data[i++] = 0x00;
00125     }
00126     else {
00127         ctx->data[i++] = 0x80;
00128         while (i < 64)
00129             ctx->data[i++] = 0x00;
00130         sha256_transform(ctx, ctx->data);
00131         memset(ctx->data, 0, 56);
00132     }
00133 
00134     // Append to the padding the total message's length in bits and transform.
00135     ctx->bitlen += ctx->datalen * 8;
00136     ctx->data[63] = ctx->bitlen;
00137     ctx->data[62] = ctx->bitlen >> 8;
00138     ctx->data[61] = ctx->bitlen >> 16;
00139     ctx->data[60] = ctx->bitlen >> 24;
00140     ctx->data[59] = ctx->bitlen >> 32;
00141     ctx->data[58] = ctx->bitlen >> 40;
00142     ctx->data[57] = ctx->bitlen >> 48;
00143     ctx->data[56] = ctx->bitlen >> 56;
00144     sha256_transform(ctx, ctx->data);
00145 
00146     // Since this implementation uses little endian byte ordering and SHA uses big endian,
00147     // reverse all the bytes when copying the final state to the output hash.
00148     for (i = 0; i < 4; ++i) {
00149         hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
00150         hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
00151         hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
00152         hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
00153         hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
00154         hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
00155         hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
00156         hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
00157     }
00158 }