/*
20080912
D. J. Bernstein
Public domain.
*/

#include "Constants.hpp"
#include "Poly1305.hpp"

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#ifdef __WINDOWS__
#pragma warning(disable: 4146)
#endif

namespace ZeroTier {

#if 0

static inline void add(unsigned int h[17],const unsigned int c[17])
{
  unsigned int j;
  unsigned int u;
  u = 0;
  for (j = 0;j < 17;++j) { u += h[j] + c[j]; h[j] = u & 255; u >>= 8; }
}

static inline void squeeze(unsigned int h[17])
{
  unsigned int j;
  unsigned int u;
  u = 0;
  for (j = 0;j < 16;++j) { u += h[j]; h[j] = u & 255; u >>= 8; }
  u += h[16]; h[16] = u & 3;
  u = 5 * (u >> 2);
  for (j = 0;j < 16;++j) { u += h[j]; h[j] = u & 255; u >>= 8; }
  u += h[16]; h[16] = u;
}

static const unsigned int minusp[17] = {
  5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 252
} ;

static inline void freeze(unsigned int h[17])
{
  unsigned int horig[17];
  unsigned int j;
  unsigned int negative;
  for (j = 0;j < 17;++j) horig[j] = h[j];
  add(h,minusp);
  negative = -(h[16] >> 7);
  for (j = 0;j < 17;++j) h[j] ^= negative & (horig[j] ^ h[j]);
}

static inline void mulmod(unsigned int h[17],const unsigned int r[17])
{
  unsigned int hr[17];
  unsigned int i;
  unsigned int j;
  unsigned int u;

  for (i = 0;i < 17;++i) {
    u = 0;
    for (j = 0;j <= i;++j) u += h[j] * r[i - j];
    for (j = i + 1;j < 17;++j) u += 320 * h[j] * r[i + 17 - j];
    hr[i] = u;
  }
  for (i = 0;i < 17;++i) h[i] = hr[i];
  squeeze(h);
}

static inline int crypto_onetimeauth(unsigned char *out,const unsigned char *in,unsigned long long inlen,const unsigned char *k)
{
  unsigned int j;
  unsigned int r[17];
  unsigned int h[17];
  unsigned int c[17];

  r[0] = k[0];
  r[1] = k[1];
  r[2] = k[2];
  r[3] = k[3] & 15;
  r[4] = k[4] & 252;
  r[5] = k[5];
  r[6] = k[6];
  r[7] = k[7] & 15;
  r[8] = k[8] & 252;
  r[9] = k[9];
  r[10] = k[10];
  r[11] = k[11] & 15;
  r[12] = k[12] & 252;
  r[13] = k[13];
  r[14] = k[14];
  r[15] = k[15] & 15;
  r[16] = 0;

  for (j = 0;j < 17;++j) h[j] = 0;

  while (inlen > 0) {
    for (j = 0;j < 17;++j) c[j] = 0;
    for (j = 0;(j < 16) && (j < inlen);++j) c[j] = in[j];
    c[j] = 1;
    in += j; inlen -= j;
    add(h,c);
    mulmod(h,r);
  }

  freeze(h);

  for (j = 0;j < 16;++j) c[j] = k[j + 16];
  c[16] = 0;
  add(h,c);
  for (j = 0;j < 16;++j) out[j] = h[j];
  return 0;
}

void Poly1305::compute(void *auth,const void *data,unsigned int len,const void *key)
	throw()
{
	crypto_onetimeauth((unsigned char *)auth,(const unsigned char *)data,len,(const unsigned char *)key);
}

#endif

namespace {

typedef struct poly1305_context {
  size_t aligner;
  unsigned char opaque[136];
} poly1305_context;

/*
  poly1305 implementation using 32 bit * 32 bit = 64 bit multiplication and 64 bit addition
*/

#define poly1305_block_size 16

/* 17 + sizeof(size_t) + 14*sizeof(unsigned long) */
typedef struct poly1305_state_internal_t {
  unsigned long r[5];
  unsigned long h[5];
  unsigned long pad[4];
  size_t leftover;
  unsigned char buffer[poly1305_block_size];
  unsigned char final;
} poly1305_state_internal_t;

/* interpret four 8 bit unsigned integers as a 32 bit unsigned integer in little endian */
static unsigned long
U8TO32(const unsigned char *p) {
  return
    (((unsigned long)(p[0] & 0xff)      ) |
       ((unsigned long)(p[1] & 0xff) <<  8) |
         ((unsigned long)(p[2] & 0xff) << 16) |
         ((unsigned long)(p[3] & 0xff) << 24));
}

/* store a 32 bit unsigned integer as four 8 bit unsigned integers in little endian */
static void
U32TO8(unsigned char *p, unsigned long v) {
  p[0] = (v      ) & 0xff;
  p[1] = (v >>  8) & 0xff;
  p[2] = (v >> 16) & 0xff;
  p[3] = (v >> 24) & 0xff;
}

static inline void
poly1305_init(poly1305_context *ctx, const unsigned char key[32]) {
  poly1305_state_internal_t *st = (poly1305_state_internal_t *)ctx;

  /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
  st->r[0] = (U8TO32(&key[ 0])     ) & 0x3ffffff;
  st->r[1] = (U8TO32(&key[ 3]) >> 2) & 0x3ffff03;
  st->r[2] = (U8TO32(&key[ 6]) >> 4) & 0x3ffc0ff;
  st->r[3] = (U8TO32(&key[ 9]) >> 6) & 0x3f03fff;
  st->r[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff;

  /* h = 0 */
  st->h[0] = 0;
  st->h[1] = 0;
  st->h[2] = 0;
  st->h[3] = 0;
  st->h[4] = 0;

  /* save pad for later */
  st->pad[0] = U8TO32(&key[16]);
  st->pad[1] = U8TO32(&key[20]);
  st->pad[2] = U8TO32(&key[24]);
  st->pad[3] = U8TO32(&key[28]);

  st->leftover = 0;
  st->final = 0;
}

static inline void
poly1305_blocks(poly1305_state_internal_t *st, const unsigned char *m, size_t bytes) {
  const unsigned long hibit = (st->final) ? 0 : (1 << 24); /* 1 << 128 */
  unsigned long r0,r1,r2,r3,r4;
  unsigned long s1,s2,s3,s4;
  unsigned long h0,h1,h2,h3,h4;
  unsigned long long d0,d1,d2,d3,d4;
  unsigned long c;

  r0 = st->r[0];
  r1 = st->r[1];
  r2 = st->r[2];
  r3 = st->r[3];
  r4 = st->r[4];

  s1 = r1 * 5;
  s2 = r2 * 5;
  s3 = r3 * 5;
  s4 = r4 * 5;

  h0 = st->h[0];
  h1 = st->h[1];
  h2 = st->h[2];
  h3 = st->h[3];
  h4 = st->h[4];

  while (bytes >= poly1305_block_size) {
    /* h += m[i] */
    h0 += (U8TO32(m+ 0)     ) & 0x3ffffff;
    h1 += (U8TO32(m+ 3) >> 2) & 0x3ffffff;
    h2 += (U8TO32(m+ 6) >> 4) & 0x3ffffff;
    h3 += (U8TO32(m+ 9) >> 6) & 0x3ffffff;
    h4 += (U8TO32(m+12) >> 8) | hibit;

    /* h *= r */
    d0 = ((unsigned long long)h0 * r0) + ((unsigned long long)h1 * s4) + ((unsigned long long)h2 * s3) + ((unsigned long long)h3 * s2) + ((unsigned long long)h4 * s1);
    d1 = ((unsigned long long)h0 * r1) + ((unsigned long long)h1 * r0) + ((unsigned long long)h2 * s4) + ((unsigned long long)h3 * s3) + ((unsigned long long)h4 * s2);
    d2 = ((unsigned long long)h0 * r2) + ((unsigned long long)h1 * r1) + ((unsigned long long)h2 * r0) + ((unsigned long long)h3 * s4) + ((unsigned long long)h4 * s3);
    d3 = ((unsigned long long)h0 * r3) + ((unsigned long long)h1 * r2) + ((unsigned long long)h2 * r1) + ((unsigned long long)h3 * r0) + ((unsigned long long)h4 * s4);
    d4 = ((unsigned long long)h0 * r4) + ((unsigned long long)h1 * r3) + ((unsigned long long)h2 * r2) + ((unsigned long long)h3 * r1) + ((unsigned long long)h4 * r0);

    /* (partial) h %= p */
                  c = (unsigned long)(d0 >> 26); h0 = (unsigned long)d0 & 0x3ffffff;
    d1 += c;      c = (unsigned long)(d1 >> 26); h1 = (unsigned long)d1 & 0x3ffffff;
    d2 += c;      c = (unsigned long)(d2 >> 26); h2 = (unsigned long)d2 & 0x3ffffff;
    d3 += c;      c = (unsigned long)(d3 >> 26); h3 = (unsigned long)d3 & 0x3ffffff;
    d4 += c;      c = (unsigned long)(d4 >> 26); h4 = (unsigned long)d4 & 0x3ffffff;
    h0 += c * 5;  c =                (h0 >> 26); h0 =                h0 & 0x3ffffff;
    h1 += c;

    m += poly1305_block_size;
    bytes -= poly1305_block_size;
  }

  st->h[0] = h0;
  st->h[1] = h1;
  st->h[2] = h2;
  st->h[3] = h3;
  st->h[4] = h4;
}

static inline void
poly1305_update(poly1305_context *ctx, const unsigned char *m, size_t bytes) {
  poly1305_state_internal_t *st = (poly1305_state_internal_t *)ctx;
  size_t i;

  /* handle leftover */
  if (st->leftover) {
    size_t want = (poly1305_block_size - st->leftover);
    if (want > bytes)
      want = bytes;
    for (i = 0; i < want; i++)
      st->buffer[st->leftover + i] = m[i];
    bytes -= want;
    m += want;
    st->leftover += want;
    if (st->leftover < poly1305_block_size)
      return;
    poly1305_blocks(st, st->buffer, poly1305_block_size);
    st->leftover = 0;
  }

  /* process full blocks */
  if (bytes >= poly1305_block_size) {
    size_t want = (bytes & ~(poly1305_block_size - 1));
    poly1305_blocks(st, m, want);
    m += want;
    bytes -= want;
  }

  /* store leftover */
  if (bytes) {
    for (i = 0; i < bytes; i++)
      st->buffer[st->leftover + i] = m[i];
    st->leftover += bytes;
  }
}

static inline void
poly1305_finish(poly1305_context *ctx, unsigned char mac[16]) {
  poly1305_state_internal_t *st = (poly1305_state_internal_t *)ctx;
  unsigned long h0,h1,h2,h3,h4,c;
  unsigned long g0,g1,g2,g3,g4;
  unsigned long long f;
  unsigned long mask;

  /* process the remaining block */
  if (st->leftover) {
    size_t i = st->leftover;
    st->buffer[i++] = 1;
    for (; i < poly1305_block_size; i++)
      st->buffer[i] = 0;
    st->final = 1;
    poly1305_blocks(st, st->buffer, poly1305_block_size);
  }

  /* fully carry h */
  h0 = st->h[0];
  h1 = st->h[1];
  h2 = st->h[2];
  h3 = st->h[3];
  h4 = st->h[4];

               c = h1 >> 26; h1 = h1 & 0x3ffffff;
  h2 +=     c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
  h3 +=     c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
  h4 +=     c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
  h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
  h1 +=     c;

  /* compute h + -p */
  g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
  g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
  g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
  g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
  g4 = h4 + c - (1 << 26);

  /* select h if h < p, or h + -p if h >= p */
  mask = (g4 >> ((sizeof(unsigned long) * 8) - 1)) - 1;
  g0 &= mask;
  g1 &= mask;
  g2 &= mask;
  g3 &= mask;
  g4 &= mask;
  mask = ~mask;
  h0 = (h0 & mask) | g0;
  h1 = (h1 & mask) | g1;
  h2 = (h2 & mask) | g2;
  h3 = (h3 & mask) | g3;
  h4 = (h4 & mask) | g4;

  /* h = h % (2^128) */
  h0 = ((h0      ) | (h1 << 26)) & 0xffffffff;
  h1 = ((h1 >>  6) | (h2 << 20)) & 0xffffffff;
  h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
  h3 = ((h3 >> 18) | (h4 <<  8)) & 0xffffffff;

  /* mac = (h + pad) % (2^128) */
  f = (unsigned long long)h0 + st->pad[0]            ; h0 = (unsigned long)f;
  f = (unsigned long long)h1 + st->pad[1] + (f >> 32); h1 = (unsigned long)f;
  f = (unsigned long long)h2 + st->pad[2] + (f >> 32); h2 = (unsigned long)f;
  f = (unsigned long long)h3 + st->pad[3] + (f >> 32); h3 = (unsigned long)f;

  U32TO8(mac +  0, h0);
  U32TO8(mac +  4, h1);
  U32TO8(mac +  8, h2);
  U32TO8(mac + 12, h3);

  /* zero out the state */
  st->h[0] = 0;
  st->h[1] = 0;
  st->h[2] = 0;
  st->h[3] = 0;
  st->h[4] = 0;
  st->r[0] = 0;
  st->r[1] = 0;
  st->r[2] = 0;
  st->r[3] = 0;
  st->r[4] = 0;
  st->pad[0] = 0;
  st->pad[1] = 0;
  st->pad[2] = 0;
  st->pad[3] = 0;
}

} // anonymous namespace

void Poly1305::compute(void *auth,const void *data,unsigned int len,const void *key)
  throw()
{
  poly1305_context ctx;
  poly1305_init(&ctx,reinterpret_cast<const unsigned char *>(key));
  poly1305_update(&ctx,reinterpret_cast<const unsigned char *>(data),(size_t)len);
  poly1305_finish(&ctx,reinterpret_cast<unsigned char *>(auth));
}

} // namespace ZeroTier