path: root/md5.c

/*
 * Implement MsiGetFileHash().
 *
 * Experimenting with a small test program on Windows calling the
 * original version of that function suggests that the hash it
 * implements is just MD5, only repackaged as an array of four
 * little-endian 32-bit words instead of the usual 16 bytes.
 */

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdbool.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <err.h>

#include "memory.h"
#include "uchars.h"

/* ----------------------------------------------------------------------
 * Core MD5 algorithm: processes 16-word blocks into a message digest.
 */

typedef struct {
    uint32_t h[4];
} MD5_Core_State;

struct MD5Context {
    MD5_Core_State core;
    unsigned char block[64];
    int blkused;
    uint64_t len;
};

#define F(x,y,z) ( ((x) & (y)) | ((~(x)) & (z)) )
#define G(x,y,z) ( ((x) & (z)) | ((~(z)) & (y)) )
#define H(x,y,z) ( (x) ^ (y) ^ (z) )
#define I(x,y,z) ( (y) ^ ( (x) | ~(z) ) )

#define rol(x,y) ( ((x) << (y)) | (((uint32_t)x) >> (32-y)) )

#define subround(f,w,x,y,z,k,s,ti) \
       w = x + rol(w + f(x,y,z) + block[k] + ti, s)

static void MD5_Core_Init(MD5_Core_State * s)
{
    s->h[0] = 0x67452301;
    s->h[1] = 0xefcdab89;
    s->h[2] = 0x98badcfe;
    s->h[3] = 0x10325476;
}

static void MD5_Block(MD5_Core_State * s, uint32_t * block)
{
    uint32_t a, b, c, d;

    a = s->h[0];
    b = s->h[1];
    c = s->h[2];
    d = s->h[3];

    subround(F, a, b, c, d, 0, 7, 0xd76aa478);
    subround(F, d, a, b, c, 1, 12, 0xe8c7b756);
    subround(F, c, d, a, b, 2, 17, 0x242070db);
    subround(F, b, c, d, a, 3, 22, 0xc1bdceee);
    subround(F, a, b, c, d, 4, 7, 0xf57c0faf);
    subround(F, d, a, b, c, 5, 12, 0x4787c62a);
    subround(F, c, d, a, b, 6, 17, 0xa8304613);
    subround(F, b, c, d, a, 7, 22, 0xfd469501);
    subround(F, a, b, c, d, 8, 7, 0x698098d8);
    subround(F, d, a, b, c, 9, 12, 0x8b44f7af);
    subround(F, c, d, a, b, 10, 17, 0xffff5bb1);
    subround(F, b, c, d, a, 11, 22, 0x895cd7be);
    subround(F, a, b, c, d, 12, 7, 0x6b901122);
    subround(F, d, a, b, c, 13, 12, 0xfd987193);
    subround(F, c, d, a, b, 14, 17, 0xa679438e);
    subround(F, b, c, d, a, 15, 22, 0x49b40821);
    subround(G, a, b, c, d, 1, 5, 0xf61e2562);
    subround(G, d, a, b, c, 6, 9, 0xc040b340);
    subround(G, c, d, a, b, 11, 14, 0x265e5a51);
    subround(G, b, c, d, a, 0, 20, 0xe9b6c7aa);
    subround(G, a, b, c, d, 5, 5, 0xd62f105d);
    subround(G, d, a, b, c, 10, 9, 0x02441453);
    subround(G, c, d, a, b, 15, 14, 0xd8a1e681);
    subround(G, b, c, d, a, 4, 20, 0xe7d3fbc8);
    subround(G, a, b, c, d, 9, 5, 0x21e1cde6);
    subround(G, d, a, b, c, 14, 9, 0xc33707d6);
    subround(G, c, d, a, b, 3, 14, 0xf4d50d87);
    subround(G, b, c, d, a, 8, 20, 0x455a14ed);
    subround(G, a, b, c, d, 13, 5, 0xa9e3e905);
    subround(G, d, a, b, c, 2, 9, 0xfcefa3f8);
    subround(G, c, d, a, b, 7, 14, 0x676f02d9);
    subround(G, b, c, d, a, 12, 20, 0x8d2a4c8a);
    subround(H, a, b, c, d, 5, 4, 0xfffa3942);
    subround(H, d, a, b, c, 8, 11, 0x8771f681);
    subround(H, c, d, a, b, 11, 16, 0x6d9d6122);
    subround(H, b, c, d, a, 14, 23, 0xfde5380c);
    subround(H, a, b, c, d, 1, 4, 0xa4beea44);
    subround(H, d, a, b, c, 4, 11, 0x4bdecfa9);
    subround(H, c, d, a, b, 7, 16, 0xf6bb4b60);
    subround(H, b, c, d, a, 10, 23, 0xbebfbc70);
    subround(H, a, b, c, d, 13, 4, 0x289b7ec6);
    subround(H, d, a, b, c, 0, 11, 0xeaa127fa);
    subround(H, c, d, a, b, 3, 16, 0xd4ef3085);
    subround(H, b, c, d, a, 6, 23, 0x04881d05);
    subround(H, a, b, c, d, 9, 4, 0xd9d4d039);
    subround(H, d, a, b, c, 12, 11, 0xe6db99e5);
    subround(H, c, d, a, b, 15, 16, 0x1fa27cf8);
    subround(H, b, c, d, a, 2, 23, 0xc4ac5665);
    subround(I, a, b, c, d, 0, 6, 0xf4292244);
    subround(I, d, a, b, c, 7, 10, 0x432aff97);
    subround(I, c, d, a, b, 14, 15, 0xab9423a7);
    subround(I, b, c, d, a, 5, 21, 0xfc93a039);
    subround(I, a, b, c, d, 12, 6, 0x655b59c3);
    subround(I, d, a, b, c, 3, 10, 0x8f0ccc92);
    subround(I, c, d, a, b, 10, 15, 0xffeff47d);
    subround(I, b, c, d, a, 1, 21, 0x85845dd1);
    subround(I, a, b, c, d, 8, 6, 0x6fa87e4f);
    subround(I, d, a, b, c, 15, 10, 0xfe2ce6e0);
    subround(I, c, d, a, b, 6, 15, 0xa3014314);
    subround(I, b, c, d, a, 13, 21, 0x4e0811a1);
    subround(I, a, b, c, d, 4, 6, 0xf7537e82);
    subround(I, d, a, b, c, 11, 10, 0xbd3af235);
    subround(I, c, d, a, b, 2, 15, 0x2ad7d2bb);
    subround(I, b, c, d, a, 9, 21, 0xeb86d391);

    s->h[0] += a;
    s->h[1] += b;
    s->h[2] += c;
    s->h[3] += d;
}

/* ----------------------------------------------------------------------
 * Outer MD5 algorithm: take an arbitrary length byte string,
 * convert it into 16-word blocks with the prescribed padding at
 * the end, and pass those blocks to the core MD5 algorithm.
 */

#define BLKSIZE 64

static void MD5Init(struct MD5Context *s)
{
    MD5_Core_Init(&s->core);
    s->blkused = 0;
    s->len = 0;
}

static void MD5Update(struct MD5Context *s, unsigned char const *p,
                      unsigned len)
{
    uint32_t wordblock[16];
    int i;

    /*
     * Update the length field.
     */
    s->len += len;

    while (len >= BLKSIZE - s->blkused) {
        /*
         * Complete and process a hash block.
         */
        memcpy(s->block + s->blkused, p, BLKSIZE - s->blkused);
        p += BLKSIZE - s->blkused;
        len -= BLKSIZE - s->blkused;
        /* Now process the block. Gather bytes little-endian into words */
        for (i = 0; i < 16; i++) {
            wordblock[i] =
                (((uint32_t) s->block[i * 4 + 3]) << 24) |
                (((uint32_t) s->block[i * 4 + 2]) << 16) |
                (((uint32_t) s->block[i * 4 + 1]) << 8) |
                (((uint32_t) s->block[i * 4 + 0]) << 0);
        }
        MD5_Block(&s->core, wordblock);
        s->blkused = 0;
    }

    if (len > 0) {
	/*
	 * Append to the block.
	 */
	memcpy(s->block + s->blkused, p, len);
	s->blkused += len;
    }
}

static void MD5Final(uint32_t output[4], struct MD5Context *s)
{
    int i;
    unsigned pad;
    unsigned char c[64];
    uint64_t len;

    if (s->blkused >= 56)
	pad = 56 + 64 - s->blkused;
    else
	pad = 56 - s->blkused;

    len = s->len << 3;

    memset(c, 0, pad);
    c[0] = 0x80;
    MD5Update(s, c, pad);

    for (i = 0; i < 8; i++)
        c[i] = (len >> (8*i)) & 0xFF;
    MD5Update(s, c, 8);

    for (i = 0; i < 4; i++)
        output[i] = s->core.h[i];
}

struct MsiHash {
    uint32_t structure_size;
    uint32_t hash_words[4];
};

uint32_t MsiGetFileHashW(const char16_t *filename, uint32_t options,
                         struct MsiHash *hash)
{
    char *fname = ascii(filename, true);
    uint32_t toret;
    char buffer[4096];
    int fd = -1, retd;
    struct MD5Context ctx;

    fd = open(fname, O_RDONLY);
    if (fd < 0) {
        /* Could do some better errno -> GetLastError translation here */
        warnx("MsiGetFileHash(%s) -> ERROR_OPEN_FAILED", fname);
        toret = 110;
        goto cleanup;
    }

    MD5Init(&ctx);

    while ((retd = read(fd, buffer, sizeof(buffer))) > 0)
        MD5Update(&ctx, buffer, retd);
    if (retd < 0) {
        warnx("MsiGetFileHash(%s) -> ERROR_READ_FAULT", fname);
        toret = 30;
        goto cleanup;
    }

    MD5Final(hash->hash_words, &ctx);

    warnx("MsiGetFileHash(%s) -> %08x:%08x:%08x:%08x", fname,
          (unsigned)hash->hash_words[0], (unsigned)hash->hash_words[1],
          (unsigned)hash->hash_words[2], (unsigned)hash->hash_words[3]);
    toret = 0;

  cleanup:
    if (fd != -1)
        close(fd);
    sfree(fname);
    return toret;
}