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/*
* chacha-merged.c version 20080118
* D. J. Bernstein
* Public domain.
* Copyright not intended 2024.
*
* SPDX-License-Identifier: SAX-PD-2.0
*/
#include "libssh2_priv.h"
#include "chacha.h"
/* $OpenBSD: chacha.c,v 1.1 2013/11/21 00:45:44 djm Exp $ */
typedef unsigned char u8;
typedef unsigned int u32;
typedef struct chacha_ctx chacha_ctx;
#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[17] = "expand 32-byte k";
static const char tau[17] = "expand 16-byte k";
void
chacha_keysetup(chacha_ctx *x, const u8 *k, u32 kbits)
{
const char *constants;
x->input[4] = U8TO32_LITTLE(k + 0);
x->input[5] = U8TO32_LITTLE(k + 4);
x->input[6] = U8TO32_LITTLE(k + 8);
x->input[7] = U8TO32_LITTLE(k + 12);
if(kbits == 256) { /* recommended */
k += 16;
constants = sigma;
}
else { /* kbits == 128 */
constants = tau;
}
x->input[8] = U8TO32_LITTLE(k + 0);
x->input[9] = U8TO32_LITTLE(k + 4);
x->input[10] = U8TO32_LITTLE(k + 8);
x->input[11] = U8TO32_LITTLE(k + 12);
x->input[0] = U8TO32_LITTLE(constants + 0);
x->input[1] = U8TO32_LITTLE(constants + 4);
x->input[2] = U8TO32_LITTLE(constants + 8);
x->input[3] = U8TO32_LITTLE(constants + 12);
}
void
chacha_ivsetup(chacha_ctx *x, const u8 *iv, const u8 *counter)
{
x->input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
x->input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
x->input[14] = U8TO32_LITTLE(iv + 0);
x->input[15] = U8TO32_LITTLE(iv + 4);
}
void
chacha_encrypt_bytes(chacha_ctx *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->input[0];
j1 = x->input[1];
j2 = x->input[2];
j3 = x->input[3];
j4 = x->input[4];
j5 = x->input[5];
j6 = x->input[6];
j7 = x->input[7];
j8 = x->input[8];
j9 = x->input[9];
j10 = x->input[10];
j11 = x->input[11];
j12 = x->input[12];
j13 = x->input[13];
j14 = x->input[14];
j15 = x->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);
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));
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->input[12] = j12;
x->input[13] = j13;
return;
}
bytes -= 64;
c += 64;
m += 64;
}
}
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