/* $OpenBSD: chacha-merged.c,v 1.10 2021/10/22 17:43:00 tb Exp $ */

/*

chacha-merged.c version 20080118

D. J. Bernstein

Public domain.

*/

#include <stdint.h>

#define CHACHA_MINKEYLEN  16

#define CHACHA_NONCELEN   8

#define CHACHA_CTRLEN   8

#define CHACHA_STATELEN   (CHACHA_NONCELEN+CHACHA_CTRLEN)

#define CHACHA_BLOCKLEN   64

typedef uint8_t u8;

typedef uint32_t u32;

struct chacha_ctx {

  u32 input[16];

  u8 ks[CHACHA_BLOCKLEN];

  u8 unused;

};

static inline void chacha_keysetup(struct chacha_ctx *x, const u8 *k, u32 kbits)

    __attribute__((__bounded__(__minbytes__, 2, CHACHA_MINKEYLEN)));

static inline void chacha_ivsetup(struct chacha_ctx *x, const u8 *iv,

    const u8 *ctr)

    __attribute__((__bounded__(__minbytes__, 2, CHACHA_NONCELEN)))

    __attribute__((__bounded__(__minbytes__, 3, CHACHA_CTRLEN)));

static inline void chacha_encrypt_bytes(struct chacha_ctx *x, const u8 *m,

    u8 *c, u32 bytes)

    __attribute__((__bounded__(__buffer__, 2, 4)))

    __attribute__((__bounded__(__buffer__, 3, 4)));

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);

/* Initialise with "expand 32-byte k". */

static const char sigma[16] = {

  0x65, 0x78, 0x70, 0x61, 0x6e, 0x64, 0x20, 0x33,

  0x32, 0x2d, 0x62, 0x79, 0x74, 0x65, 0x20, 0x6b,

};

/* Initialise with "expand 16-byte k". */

static const char tau[16] = {

  0x65, 0x78, 0x70, 0x61, 0x6e, 0x64, 0x20, 0x31,

  0x36, 0x2d, 0x62, 0x79, 0x74, 0x65, 0x20, 0x6b,

};

static inline 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);

}

static inline 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);

}

static inline void

chacha_encrypt_bytes(chacha_ctx *x, const u8 *m, u8 *c, u32 bytes)

{

  u32 x0, x1, x2, x3, x4, x5, x6, x7;

  u32 x8, x9, x10, x11, x12, x13, x14, x15;

  u32 j0, j1, j2, j3, j4, j5, j6, j7;

  u32 j8, j9, j10, j11, j12, j13, j14, j15;

  u8 *ctarget = NULL;

  u8 tmp[64];

  u32 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);

    if (bytes < 64) {

      U32TO8_LITTLE(x->ks + 0, x0);

      U32TO8_LITTLE(x->ks + 4, x1);

      U32TO8_LITTLE(x->ks + 8, x2);

      U32TO8_LITTLE(x->ks + 12, x3);

      U32TO8_LITTLE(x->ks + 16, x4);

      U32TO8_LITTLE(x->ks + 20, x5);

      U32TO8_LITTLE(x->ks + 24, x6);

      U32TO8_LITTLE(x->ks + 28, x7);

      U32TO8_LITTLE(x->ks + 32, x8);

      U32TO8_LITTLE(x->ks + 36, x9);

      U32TO8_LITTLE(x->ks + 40, x10);

      U32TO8_LITTLE(x->ks + 44, x11);

      U32TO8_LITTLE(x->ks + 48, x12);

      U32TO8_LITTLE(x->ks + 52, x13);

      U32TO8_LITTLE(x->ks + 56, x14);

      U32TO8_LITTLE(x->ks + 60, x15);

    }

    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 the 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;

      x->unused = 64 - bytes;

      return;

    }

    bytes -= 64;

    c += 64;

    m += 64;

  }

}

void

CRYPTO_hchacha_20(unsigned char subkey[32], const unsigned char key[32],

    const unsigned char nonce[16])

{

  uint32_t x[16];

  int i;

  x[0] = U8TO32_LITTLE(sigma + 0);

  x[1] = U8TO32_LITTLE(sigma + 4);

  x[2] = U8TO32_LITTLE(sigma + 8);

  x[3] = U8TO32_LITTLE(sigma + 12);

  x[4] = U8TO32_LITTLE(key + 0);

  x[5] = U8TO32_LITTLE(key + 4);

  x[6] = U8TO32_LITTLE(key + 8);

  x[7] = U8TO32_LITTLE(key + 12);

  x[8] = U8TO32_LITTLE(key + 16);

  x[9] = U8TO32_LITTLE(key + 20);

  x[10] = U8TO32_LITTLE(key + 24);

  x[11] = U8TO32_LITTLE(key + 28);

  x[12] = U8TO32_LITTLE(nonce + 0);

  x[13] = U8TO32_LITTLE(nonce + 4);

  x[14] = U8TO32_LITTLE(nonce + 8);

  x[15] = U8TO32_LITTLE(nonce + 12);

  for (i = 20; i > 0; i -= 2) {

    QUARTERROUND(x[0], x[4], x[8], x[12])

    QUARTERROUND(x[1], x[5], x[9], x[13])

    QUARTERROUND(x[2], x[6], x[10], x[14])

    QUARTERROUND(x[3], x[7], x[11], x[15])

    QUARTERROUND(x[0], x[5], x[10], x[15])

    QUARTERROUND(x[1], x[6], x[11], x[12])

    QUARTERROUND(x[2], x[7], x[8], x[13])

    QUARTERROUND(x[3], x[4], x[9], x[14])

  }

  U32TO8_LITTLE(subkey + 0, x[0]);

  U32TO8_LITTLE(subkey + 4, x[1]);

  U32TO8_LITTLE(subkey + 8, x[2]);

  U32TO8_LITTLE(subkey + 12, x[3]);

  U32TO8_LITTLE(subkey + 16, x[12]);

  U32TO8_LITTLE(subkey + 20, x[13]);

  U32TO8_LITTLE(subkey + 24, x[14]);

  U32TO8_LITTLE(subkey + 28, x[15]);

}