对md5sum程序的修改

linux下自带md5sum工具，可以对文件计算md5值，但这个命令行工具不能直接对字符串求md5，而对一个字符串求md5是一个比较有用的需求，比如计算签名。于是对源码md5sum.c修改了一番，可以通过命令行计算字符串的md5值了，比如输入：md5sum admin或者md5sum "admin"

回车后打印出：21232f297a57a5a743894a0e4a801fc3

这正是我想要的。如果把要计算md5的字符串存到txt文件里，再对文件计算md5值，往往会得不到正确的结果，因为vi或者gedit会在保存文件的时候多加一个换行符。

下面贴出源码，希望能帮到有需要这个的人。编译命令：gcc -Wall -o md5sum md5sum.c

/* md5sum.c - print MD5 Message-Digest Algorithm
 * Copyright (C) 1995, 1996, 1998, 1999,
 *               2000, 2001, 2002 Free Software Foundation, Inc.
 *
 * 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, 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * According to the definition of MD5 in RFC 1321 from April 1992.
 * NOTE: This is *not* the same file as the one from glibc.
 */
 /* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */
 /* Heavily modified for GnuPG by <wk@gnupg.org> */

 /* Test values:
  * ""                  D4 1D 8C D9 8F 00 B2 04  E9 80 09 98 EC F8 42 7E
  * "a"                 0C C1 75 B9 C0 F1 B6 A8  31 C3 99 E2 69 77 26 61
  * "abc"               90 01 50 98 3C D2 4F B0  D6 96 3F 7D 28 E1 7F 72
  * "message digest"    F9 6B 69 7D 7C B7 93 8D  52 5A 2F 31 AA F1 61 D0
  */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

#undef BIG_ENDIAN_HOST
typedef unsigned int u32;

/****************
 * Rotate a 32 bit integer by n bytes
 */
#if defined(__GNUC__) && defined(__i386__)
static inline u32
rol(u32 x, int n)
{
    __asm__("roll %%cl,%0"
        :"=r" (x)
        : "0" (x), "c" (n));
    return x;
}
#else
#define rol(x,n) ( ((x) << (n)) | ((x) >> (32-(n))) )
#endif

typedef struct {
    u32 A, B, C, D;      /* chaining variables */
    u32  nblocks;
    unsigned char buf[64];
    int  count;
} MD5_CONTEXT;

static void md5_init(MD5_CONTEXT* ctx)
{
    ctx->A = 0x67452301;
    ctx->B = 0xefcdab89;
    ctx->C = 0x98badcfe;
    ctx->D = 0x10325476;


    ctx->nblocks = 0;
    ctx->count = 0;
}

/* These are the four functions used in the four steps of the MD5 algorithm
   and defined in the RFC 1321.  The first function is a little bit optimized
   (as found in Colin Plumbs public domain implementation).  */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF (d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))

/****************
 * transform n*64 bytes
 */
static void transform(MD5_CONTEXT* ctx, unsigned char* data)
{
    u32 correct_words[16];
    u32 A = ctx->A;
    u32 B = ctx->B;
    u32 C = ctx->C;
    u32 D = ctx->D;
    u32* cwp = correct_words;


#ifdef BIG_ENDIAN_HOST
    { int i;
    unsigned char* p2, * p1;
    for (i = 0, p1 = data, p2 = (unsigned char*)correct_words; i < 16; i++, p2 += 4) {
        p2[3] = *p1++;
        p2[2] = *p1++;
        p2[1] = *p1++;
        p2[0] = *p1++;
    }
    }
#else
    memcpy(correct_words, data, 64);
#endif


#define OP(a, b, c, d, s, T)                        \
  do                                    \
    {                                    \
      a += FF (b, c, d) + (*cwp++) + T;         \
      a = rol(a, s);                            \
      a += b;                                \
    }                                    \
  while (0)


    /* Before we start, one word about the strange constants.
       They are defined in RFC 1321 as
       T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
     */


     /* Round 1.  */
    OP(A, B, C, D, 7, 0xd76aa478);
    OP(D, A, B, C, 12, 0xe8c7b756);
    OP(C, D, A, B, 17, 0x242070db);
    OP(B, C, D, A, 22, 0xc1bdceee);
    OP(A, B, C, D, 7, 0xf57c0faf);
    OP(D, A, B, C, 12, 0x4787c62a);
    OP(C, D, A, B, 17, 0xa8304613);
    OP(B, C, D, A, 22, 0xfd469501);
    OP(A, B, C, D, 7, 0x698098d8);
    OP(D, A, B, C, 12, 0x8b44f7af);
    OP(C, D, A, B, 17, 0xffff5bb1);
    OP(B, C, D, A, 22, 0x895cd7be);
    OP(A, B, C, D, 7, 0x6b901122);
    OP(D, A, B, C, 12, 0xfd987193);
    OP(C, D, A, B, 17, 0xa679438e);
    OP(B, C, D, A, 22, 0x49b40821);


#undef OP
#define OP(f, a, b, c, d, k, s, T)  \
    do                                      \
      {                                   \
    a += f (b, c, d) + correct_words[k] + T;              \
    a = rol(a, s);                              \
    a += b;                               \
      }                                   \
    while (0)


    /* Round 2.  */
    OP(FG, A, B, C, D, 1, 5, 0xf61e2562);
    OP(FG, D, A, B, C, 6, 9, 0xc040b340);
    OP(FG, C, D, A, B, 11, 14, 0x265e5a51);
    OP(FG, B, C, D, A, 0, 20, 0xe9b6c7aa);
    OP(FG, A, B, C, D, 5, 5, 0xd62f105d);
    OP(FG, D, A, B, C, 10, 9, 0x02441453);
    OP(FG, C, D, A, B, 15, 14, 0xd8a1e681);
    OP(FG, B, C, D, A, 4, 20, 0xe7d3fbc8);
    OP(FG, A, B, C, D, 9, 5, 0x21e1cde6);
    OP(FG, D, A, B, C, 14, 9, 0xc33707d6);
    OP(FG, C, D, A, B, 3, 14, 0xf4d50d87);
    OP(FG, B, C, D, A, 8, 20, 0x455a14ed);
    OP(FG, A, B, C, D, 13, 5, 0xa9e3e905);
    OP(FG, D, A, B, C, 2, 9, 0xfcefa3f8);
    OP(FG, C, D, A, B, 7, 14, 0x676f02d9);
    OP(FG, B, C, D, A, 12, 20, 0x8d2a4c8a);


    /* Round 3.  */
    OP(FH, A, B, C, D, 5, 4, 0xfffa3942);
    OP(FH, D, A, B, C, 8, 11, 0x8771f681);
    OP(FH, C, D, A, B, 11, 16, 0x6d9d6122);
    OP(FH, B, C, D, A, 14, 23, 0xfde5380c);
    OP(FH, A, B, C, D, 1, 4, 0xa4beea44);
    OP(FH, D, A, B, C, 4, 11, 0x4bdecfa9);
    OP(FH, C, D, A, B, 7, 16, 0xf6bb4b60);
    OP(FH, B, C, D, A, 10, 23, 0xbebfbc70);
    OP(FH, A, B, C, D, 13, 4, 0x289b7ec6);
    OP(FH, D, A, B, C, 0, 11, 0xeaa127fa);
    OP(FH, C, D, A, B, 3, 16, 0xd4ef3085);
    OP(FH, B, C, D, A, 6, 23, 0x04881d05);
    OP(FH, A, B, C, D, 9, 4, 0xd9d4d039);
    OP(FH, D, A, B, C, 12, 11, 0xe6db99e5);
    OP(FH, C, D, A, B, 15, 16, 0x1fa27cf8);
    OP(FH, B, C, D, A, 2, 23, 0xc4ac5665);


    /* Round 4.  */
    OP(FI, A, B, C, D, 0, 6, 0xf4292244);
    OP(FI, D, A, B, C, 7, 10, 0x432aff97);
    OP(FI, C, D, A, B, 14, 15, 0xab9423a7);
    OP(FI, B, C, D, A, 5, 21, 0xfc93a039);
    OP(FI, A, B, C, D, 12, 6, 0x655b59c3);
    OP(FI, D, A, B, C, 3, 10, 0x8f0ccc92);
    OP(FI, C, D, A, B, 10, 15, 0xffeff47d);
    OP(FI, B, C, D, A, 1, 21, 0x85845dd1);
    OP(FI, A, B, C, D, 8, 6, 0x6fa87e4f);
    OP(FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
    OP(FI, C, D, A, B, 6, 15, 0xa3014314);
    OP(FI, B, C, D, A, 13, 21, 0x4e0811a1);
    OP(FI, A, B, C, D, 4, 6, 0xf7537e82);
    OP(FI, D, A, B, C, 11, 10, 0xbd3af235);
    OP(FI, C, D, A, B, 2, 15, 0x2ad7d2bb);
    OP(FI, B, C, D, A, 9, 21, 0xeb86d391);


    /* Put checksum in context given as argument.  */
    ctx->A += A;
    ctx->B += B;
    ctx->C += C;
    ctx->D += D;
}


/* The routine updates the message-digest context to
 * account for the presence of each of the characters inBuf[0..inLen-1]
 * in the message whose digest is being computed.
 */
static void md5_write(MD5_CONTEXT* hd, unsigned char* inbuf, size_t inlen)
{
    if (hd->count == 64) { /* flush the buffer */
        transform(hd, hd->buf);
        hd->count = 0;
        hd->nblocks++;
    }
    if (!inbuf)
        return;
    if (hd->count) {
        for (; inlen && hd->count < 64; inlen--)
            hd->buf[hd->count++] = *inbuf++;
        md5_write(hd, NULL, 0);
        if (!inlen)
            return;
    }


    while (inlen >= 64) {
        transform(hd, inbuf);
        hd->count = 0;
        hd->nblocks++;
        inlen -= 64;
        inbuf += 64;
    }
    for (; inlen && hd->count < 64; inlen--)
        hd->buf[hd->count++] = *inbuf++;
}


/* The routine final terminates the message-digest computation and
 * ends with the desired message digest in mdContext->digest[0...15].
 * The handle is prepared for a new MD5 cycle.
 * Returns 16 bytes representing the digest.
 */


static void md5_final(MD5_CONTEXT* hd)
{
    u32 t, msb, lsb;
    unsigned char* p;

    md5_write(hd, NULL, 0); /* flush */;

    t = hd->nblocks;
    /* multiply by 64 to make a byte count */
    lsb = t << 6;
    msb = t >> 26;
    /* add the count */
    t = lsb;
    if ((lsb += hd->count) < t)
        msb++;
    /* multiply by 8 to make a bit count */
    t = lsb;
    lsb <<= 3;
    msb <<= 3;
    msb |= t >> 29;

    if (hd->count < 56) { /* enough room */
        hd->buf[hd->count++] = 0x80; /* pad */
        while (hd->count < 56)
            hd->buf[hd->count++] = 0;  /* pad */
    }
    else { /* need one extra block */
        hd->buf[hd->count++] = 0x80; /* pad character */
        while (hd->count < 64)
            hd->buf[hd->count++] = 0;
        md5_write(hd, NULL, 0);  /* flush */;
        memset(hd->buf, 0, 56); /* fill next block with zeroes */
    }
    /* append the 64 bit count */
    hd->buf[56] = lsb;
    hd->buf[57] = lsb >> 8;
    hd->buf[58] = lsb >> 16;
    hd->buf[59] = lsb >> 24;
    hd->buf[60] = msb;
    hd->buf[61] = msb >> 8;
    hd->buf[62] = msb >> 16;
    hd->buf[63] = msb >> 24;
    transform(hd, hd->buf);

    p = hd->buf;
#ifdef BIG_ENDIAN_HOST
#define X(a) do { *p++ = hd-> a      ; *p++ = hd-> a >> 8;      \
                  *p++ = hd-> a >> 16; *p++ = hd-> a >> 24; } while(0)
#else /* little endian */
#define X(a) do { *(u32*)p = hd-> a ; p += 4; } while(0)
#endif
    X(A);
    X(B);
    X(C);
    X(D);
#undef X
}


int main(int argc, char** argv)
{
    assert(sizeof(u32) == 4);

    if (argc < 2)
    {
        fprintf(stderr, "usage: md5sum filenames\n");
        exit(1);
    }
    /*
    for (argc--, argv++; argc; argv++, argc--)
    {
        FILE* fp;
        unsigned char buffer[4096];
        size_t n;
        MD5_CONTEXT ctx;
        int i;

        fp = fopen(*argv, "rb");
        if (!fp)
        {
            fprintf(stderr, "can't open `%s': %s\n", *argv, strerror(errno));
            exit(1);
        }

        md5_init(&ctx);
        while ((n = fread(buffer, 1, sizeof buffer, fp)))
            md5_write(&ctx, buffer, n);

        if (ferror(fp))
        {
            fprintf(stderr, "error reading `%s': %s\n", *argv, strerror(errno));
            exit(1);
        }
        md5_final(&ctx);
        fclose(fp);

        for (i = 0; i < 16; i++)
            printf("%02x", ctx.buf[i]);
        printf("  %s\n", *argv);
    }
    */
    {
	    size_t n;
	    MD5_CONTEXT ctx;
	    int i;
	    md5_init(&ctx);
            n = strlen(argv[1]);	
	    md5_write(&ctx, argv[1], n);
	    md5_final(&ctx);
	    for (i = 0; i < 16; i++)
                    printf("%02x", ctx.buf[i]);
	    printf("\n");
    }
    return 0;
}


/*
Local Variables:
compile-command: "gcc -Wall -o md5sum md5sum.c"
End:
*/