# shithub: drawterm

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```#include "os.h"
#include <libsec.h>

/*
*  This MD4 is implemented from the description in Stinson's Cryptography,
*  theory and practice. -- presotto
*/

/*
*	Rotate ammounts used in the algorithm
*/
enum
{
S11=	3,
S12=	7,
S13=	11,
S14=	19,

S21=	3,
S22=	5,
S23=	9,
S24=	13,

S31=	3,
S32=	9,
S33=	11,
S34=	15,
};

typedef struct MD4Table MD4Table;
struct MD4Table
{
uchar	x;	/* index into data block */
uchar	rot;	/* amount to rotate left by */
};

static MD4Table tab[] =
{
/* round 1 */
/*[0]*/	{ 0,	S11},
{ 1,	S12},
{ 2,	S13},
{ 3,	S14},
{ 4,	S11},
{ 5,	S12},
{ 6,	S13},
{ 7,	S14},
{ 8,	S11},
{ 9,	S12},
{ 10,	S13},
{ 11,	S14},
{ 12,	S11},
{ 13,	S12},
{ 14,	S13},
{ 15,	S14},

/* round 2 */
/*[16]*/{ 0,	S21},
{ 4,	S22},
{ 8,	S23},
{ 12,	S24},
{ 1,	S21},
{ 5,	S22},
{ 9,	S23},
{ 13,	S24},
{ 2,	S21},
{ 6,	S22},
{ 10,	S23},
{ 14,	S24},
{ 3,	S21},
{ 7,	S22},
{ 11,	S23},
{ 15,	S24},

/* round 3 */
/*[32]*/{ 0,	S31},
{ 8,	S32},
{ 4,	S33},
{ 12,	S34},
{ 2,	S31},
{ 10,	S32},
{ 6,	S33},
{ 14,	S34},
{ 1,	S31},
{ 9,	S32},
{ 5,	S33},
{ 13,	S34},
{ 3,	S31},
{ 11,	S32},
{ 7,	S33},
{ 15,	S34},
};

static void encode(uchar*, u32int*, ulong);
static void decode(u32int*, uchar*, ulong);

static void
md4block(uchar *p, ulong len, MD4state *s)
{
int i;
u32int a, b, c, d, tmp;
MD4Table *t;
uchar *end;
u32int x[16];

for(end = p+len; p < end; p += 64){
a = s->state[0];
b = s->state[1];
c = s->state[2];
d = s->state[3];

decode(x, p, 64);

for(i = 0; i < 48; i++){
t = tab + i;
switch(i>>4){
case 0:
a += (b & c) | (~b & d);
break;
case 1:
a += ((b & c) | (b & d) | (c & d)) + 0x5A827999;
break;
case 2:
a += (b ^ c ^ d) + 0x6ED9EBA1;
break;
}
a += x[t->x];
a = (a << t->rot) | (a >> (32 - t->rot));

/* rotate variables */
tmp = d;
d = c;
c = b;
b = a;
a = tmp;
}

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

s->len += 64;
}
}

MD4state*
md4(uchar *p, ulong len, uchar *digest, MD4state *s)
{
u32int x[16];
uchar buf[128];
int i;
uchar *e;

if(s == nil){
s = malloc(sizeof(*s));
if(s == nil)
return nil;
memset(s, 0, sizeof(*s));
s->malloced = 1;
}

if(s->seeded == 0){
/* seed the state, these constants would look nicer big-endian */
s->state[0] = 0x67452301;
s->state[1] = 0xefcdab89;
s->state[3] = 0x10325476;
s->seeded = 1;
}

/* fill out the partial 64 byte block from previous calls */
if(s->blen){
i = 64 - s->blen;
if(len < i)
i = len;
memmove(s->buf + s->blen, p, i);
len -= i;
s->blen += i;
p += i;
if(s->blen == 64){
md4block(s->buf, s->blen, s);
s->blen = 0;
}
}

/* do 64 byte blocks */
i = len & ~0x3f;
if(i){
md4block(p, i, s);
len -= i;
p += i;
}

/* save the left overs if not last call */
if(digest == 0){
if(len){
memmove(s->buf, p, len);
s->blen += len;
}
return s;
}

/*
*  this is the last time through, pad what's left with 0x80,
*  0's, and the input count to create a multiple of 64 bytes
*/
if(s->blen){
p = s->buf;
len = s->blen;
} else {
memmove(buf, p, len);
p = buf;
}
s->len += len;
e = p + len;
if(len < 56)
i = 56 - len;
else
i = 120 - len;
memset(e, 0, i);
*e = 0x80;
len += i;

/* append the count */
x[0] = s->len<<3;
x[1] = s->len>>29;
encode(p+len, x, 8);

/* digest the last part */
md4block(p, len+8, s);

/* return result and free state */
encode(digest, s->state, MD4dlen);
if(s->malloced == 1)
free(s);
return nil;
}

/*
*	encodes input (u32int) into output (uchar). Assumes len is
*	a multiple of 4.
*/
static void
encode(uchar *output, u32int *input, ulong len)
{
u32int x;
uchar *e;

for(e = output + len; output < e;) {
x = *input++;
*output++ = x;
*output++ = x >> 8;
*output++ = x >> 16;
*output++ = x >> 24;
}
}

/*
*	decodes input (uchar) into output (u32int). Assumes len is
*	a multiple of 4.
*/
static void
decode(u32int *output, uchar *input, ulong len)
{
uchar *e;

for(e = input+len; input < e; input += 4)
*output++ = input[0] | (input[1] << 8) |
(input[2] << 16) | (input[3] << 24);
}
```