/*

 * 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;

    }

}