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/*
* This implementation of ChaCha20 comes from the initial Dan Bernstein
* implementation, including a 256-bit key, a 64-bit nonce and a 64-bit
* counter. This is in contrast to ChaCha20 as defined in RFC 7539, which
* defines a 256-bit key, a 96-bit nonce and a 32-bit counter. In particular,
* kernel crash dump encryption relies on the fact that our larger counter
* allows for the encryption of very large messages (many gigabytes in
* length); any change to this implementation that reduces the size of the
* counter should be mindful of this use case.
*/
/*
chacha-merged.c version 20080118
D. J. Bernstein
Public domain.
*/
/* $OpenBSD: chacha.c,v 1.1 2013/11/21 00:45:44 djm Exp $ */
#include "chacha.h"
#include <sys/stddef.h>
#include <sys/null.h>
typedef unsigned char u8;
typedef unsigned int u32;
typedef unsigned int u_int;
#define U8C(v) (v##U)
#define U32C(v) (v##U)
#define U8V(v) ((u8)(v) & U8C(0xFF))
#define U32V(v) ((u32)(v) & U32C(0xFFFFFFFF))
#define ROTL32(v, n) \
(U32V((v) << (n)) | ((v) >> (32 - (n))))
#define U8TO32_LITTLE(p) \
(((u32)((p)[0]) ) | \
((u32)((p)[1]) << 8) | \
((u32)((p)[2]) << 16) | \
((u32)((p)[3]) << 24))
#define U32TO8_LITTLE(p, v) \
do { \
(p)[0] = U8V((v) ); \
(p)[1] = U8V((v) >> 8); \
(p)[2] = U8V((v) >> 16); \
(p)[3] = U8V((v) >> 24); \
} while (0)
#define ROTATE(v,c) (ROTL32(v,c))
#define XOR(v,w) ((v) ^ (w))
#define PLUS(v,w) (U32V((v) + (w)))
#define PLUSONE(v) (PLUS((v),1))
#define QUARTERROUND(a,b,c,d) \
a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
static const char sigma[16] = "expand 32-byte k";
static const char tau[16] = "expand 16-byte k";
void
chacha_keysetup(chacha_ctx_t *x,const u8 *k,u32 kbits,u32 ivbits)
{
const char *constants;
x->chacha_input[4] = U8TO32_LITTLE(k + 0);
x->chacha_input[5] = U8TO32_LITTLE(k + 4);
x->chacha_input[6] = U8TO32_LITTLE(k + 8);
x->chacha_input[7] = U8TO32_LITTLE(k + 12);
if (kbits == 256) { /* recommended */
k += 16;
constants = sigma;
} else { /* kbits == 128 */
constants = tau;
}
x->chacha_input[8] = U8TO32_LITTLE(k + 0);
x->chacha_input[9] = U8TO32_LITTLE(k + 4);
x->chacha_input[10] = U8TO32_LITTLE(k + 8);
x->chacha_input[11] = U8TO32_LITTLE(k + 12);
x->chacha_input[0] = U8TO32_LITTLE(constants + 0);
x->chacha_input[1] = U8TO32_LITTLE(constants + 4);
x->chacha_input[2] = U8TO32_LITTLE(constants + 8);
x->chacha_input[3] = U8TO32_LITTLE(constants + 12);
}
void
chacha_ivsetup(chacha_ctx_t *x,const u8 *iv, const u8 *counter)
{
x->chacha_input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
x->chacha_input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
x->chacha_input[14] = U8TO32_LITTLE(iv + 0);
x->chacha_input[15] = U8TO32_LITTLE(iv + 4);
}
void
chacha_encrypt_bytes(chacha_ctx_t *x,const u8 *m,u8 *c,u32 bytes)
{
u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
u8 *ctarget = NULL;
u8 tmp[64];
u_int i;
if (!bytes) return;
j0 = x->chacha_input[0];
j1 = x->chacha_input[1];
j2 = x->chacha_input[2];
j3 = x->chacha_input[3];
j4 = x->chacha_input[4];
j5 = x->chacha_input[5];
j6 = x->chacha_input[6];
j7 = x->chacha_input[7];
j8 = x->chacha_input[8];
j9 = x->chacha_input[9];
j10 = x->chacha_input[10];
j11 = x->chacha_input[11];
j12 = x->chacha_input[12];
j13 = x->chacha_input[13];
j14 = x->chacha_input[14];
j15 = x->chacha_input[15];
for (;;) {
if (bytes < 64) {
for (i = 0;i < bytes;++i) tmp[i] = m[i];
m = tmp;
ctarget = c;
c = tmp;
}
x0 = j0;
x1 = j1;
x2 = j2;
x3 = j3;
x4 = j4;
x5 = j5;
x6 = j6;
x7 = j7;
x8 = j8;
x9 = j9;
x10 = j10;
x11 = j11;
x12 = j12;
x13 = j13;
x14 = j14;
x15 = j15;
for (i = 20;i > 0;i -= 2) {
QUARTERROUND( x0, x4, x8,x12)
QUARTERROUND( x1, x5, x9,x13)
QUARTERROUND( x2, x6,x10,x14)
QUARTERROUND( x3, x7,x11,x15)
QUARTERROUND( x0, x5,x10,x15)
QUARTERROUND( x1, x6,x11,x12)
QUARTERROUND( x2, x7, x8,x13)
QUARTERROUND( x3, x4, x9,x14)
}
x0 = PLUS(x0,j0);
x1 = PLUS(x1,j1);
x2 = PLUS(x2,j2);
x3 = PLUS(x3,j3);
x4 = PLUS(x4,j4);
x5 = PLUS(x5,j5);
x6 = PLUS(x6,j6);
x7 = PLUS(x7,j7);
x8 = PLUS(x8,j8);
x9 = PLUS(x9,j9);
x10 = PLUS(x10,j10);
x11 = PLUS(x11,j11);
x12 = PLUS(x12,j12);
x13 = PLUS(x13,j13);
x14 = PLUS(x14,j14);
x15 = PLUS(x15,j15);
#ifndef KEYSTREAM_ONLY
x0 = XOR(x0,U8TO32_LITTLE(m + 0));
x1 = XOR(x1,U8TO32_LITTLE(m + 4));
x2 = XOR(x2,U8TO32_LITTLE(m + 8));
x3 = XOR(x3,U8TO32_LITTLE(m + 12));
x4 = XOR(x4,U8TO32_LITTLE(m + 16));
x5 = XOR(x5,U8TO32_LITTLE(m + 20));
x6 = XOR(x6,U8TO32_LITTLE(m + 24));
x7 = XOR(x7,U8TO32_LITTLE(m + 28));
x8 = XOR(x8,U8TO32_LITTLE(m + 32));
x9 = XOR(x9,U8TO32_LITTLE(m + 36));
x10 = XOR(x10,U8TO32_LITTLE(m + 40));
x11 = XOR(x11,U8TO32_LITTLE(m + 44));
x12 = XOR(x12,U8TO32_LITTLE(m + 48));
x13 = XOR(x13,U8TO32_LITTLE(m + 52));
x14 = XOR(x14,U8TO32_LITTLE(m + 56));
x15 = XOR(x15,U8TO32_LITTLE(m + 60));
#endif
j12 = PLUSONE(j12);
if (!j12) {
j13 = PLUSONE(j13);
/* stopping at 2^70 bytes per nonce is user's responsibility */
}
U32TO8_LITTLE(c + 0,x0);
U32TO8_LITTLE(c + 4,x1);
U32TO8_LITTLE(c + 8,x2);
U32TO8_LITTLE(c + 12,x3);
U32TO8_LITTLE(c + 16,x4);
U32TO8_LITTLE(c + 20,x5);
U32TO8_LITTLE(c + 24,x6);
U32TO8_LITTLE(c + 28,x7);
U32TO8_LITTLE(c + 32,x8);
U32TO8_LITTLE(c + 36,x9);
U32TO8_LITTLE(c + 40,x10);
U32TO8_LITTLE(c + 44,x11);
U32TO8_LITTLE(c + 48,x12);
U32TO8_LITTLE(c + 52,x13);
U32TO8_LITTLE(c + 56,x14);
U32TO8_LITTLE(c + 60,x15);
if (bytes <= 64) {
if (bytes < 64) {
for (i = 0;i < bytes;++i) ctarget[i] = c[i];
}
x->chacha_input[12] = j12;
x->chacha_input[13] = j13;
return;
}
bytes -= 64;
c += 64;
#ifndef KEYSTREAM_ONLY
m += 64;
#endif
}
}
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