/*

chacha-merged.c version 20080118

D. J. Bernstein

Public domain.

 */

#include <stdint.h>

#include <stddef.h>

#include <sys/types.h>

#include "libssh/chacha.h"

typedef struct chacha_ctx chacha_ctx;

#define U8C(v) (v##U)

#define U32C(v) (v##U)

#define U8V(v) ((uint8_t)(v) & U8C(0xFF))

#define U32V(v) ((uint32_t)(v) & U32C(0xFFFFFFFF))

#define ROTL32(v, n) \

        (U32V((v) << (n)) | ((v) >> (32 - (n))))

#define U8TO32_LITTLE(p) \

        (((uint32_t)((p)[0])      ) | \

         ((uint32_t)((p)[1]) <<  8) | \

         ((uint32_t)((p)[2]) << 16) | \

         ((uint32_t)((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 *x,const uint8_t *k,uint32_t 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 uint8_t *iv, const uint8_t *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 uint8_t *m,uint8_t *c,uint32_t bytes)

{

    uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;

    uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;

    uint8_t *ctarget = NULL;

    uint8_t tmp[64];

    uint32_t 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;

    }

}