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

#include "Poly1305.hpp"

#include "Constants.hpp"

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

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

namespace ZeroTier {

namespace {

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

#if (defined(_MSC_VER) || defined(__GNUC__)) && (defined(__amd64) || defined(__amd64__) || defined(__x86_64) || defined(__x86_64__) || defined(__AMD64) || defined(__AMD64__) || defined(_M_X64))

//////////////////////////////////////////////////////////////////////////////
// 128-bit implementation for MSC and GCC from Poly1305-donna

#if defined(_MSC_VER)
#include <intrin.h>

typedef struct uint128_t {
    unsigned long long lo;
    unsigned long long hi;
} uint128_t;

#define MUL(out, x, y) out.lo = _umul128((x), (y), &out.hi)
#define ADD(out, in)                                                                                                                                                                                                                           \
    {                                                                                                                                                                                                                                          \
        unsigned long long t = out.lo;                                                                                                                                                                                                         \
        out.lo += in.lo;                                                                                                                                                                                                                       \
        out.hi += (out.lo < t) + in.hi;                                                                                                                                                                                                        \
    }
#define ADDLO(out, in)                                                                                                                                                                                                                         \
    {                                                                                                                                                                                                                                          \
        unsigned long long t = out.lo;                                                                                                                                                                                                         \
        out.lo += in;                                                                                                                                                                                                                          \
        out.hi += (out.lo < t);                                                                                                                                                                                                                \
    }
#define SHR(in, shift) (__shiftright128(in.lo, in.hi, (shift)))
#define LO(in)         (in.lo)

//  #define POLY1305_NOINLINE __declspec(noinline)
#elif defined(__GNUC__)
#if defined(__SIZEOF_INT128__)
typedef unsigned __int128 uint128_t;
#else
typedef unsigned uint128_t __attribute__((mode(TI)));
#endif

#define MUL(out, x, y) out = ((uint128_t)x * y)
#define ADD(out, in)   out += in
#define ADDLO(out, in) out += in
#define SHR(in, shift) (unsigned long long)(in >> (shift))
#define LO(in)         (unsigned long long)(in)

//  #define POLY1305_NOINLINE __attribute__((noinline))
#endif

#define poly1305_block_size 16

/* 17 + sizeof(size_t) + 8*sizeof(unsigned long long) */
typedef struct poly1305_state_internal_t {
    unsigned long long r[3];
    unsigned long long h[3];
    unsigned long long pad[2];
    size_t leftover;
    unsigned char buffer[poly1305_block_size];
    unsigned char final;
} poly1305_state_internal_t;

#if defined(ZT_NO_TYPE_PUNNING) || (__BYTE_ORDER != __LITTLE_ENDIAN)
static inline unsigned long long U8TO64(const unsigned char* p)
{
    return (
        ((unsigned long long)(p[0] & 0xff)) | ((unsigned long long)(p[1] & 0xff) << 8) | ((unsigned long long)(p[2] & 0xff) << 16) | ((unsigned long long)(p[3] & 0xff) << 24) | ((unsigned long long)(p[4] & 0xff) << 32)
        | ((unsigned long long)(p[5] & 0xff) << 40) | ((unsigned long long)(p[6] & 0xff) << 48) | ((unsigned long long)(p[7] & 0xff) << 56));
}
#else
#define U8TO64(p) (*reinterpret_cast<const unsigned long long*>(p))
#endif

#if defined(ZT_NO_TYPE_PUNNING) || (__BYTE_ORDER != __LITTLE_ENDIAN)
static inline void U64TO8(unsigned char* p, unsigned long long v)
{
    p[0] = (v) & 0xff;
    p[1] = (v >> 8) & 0xff;
    p[2] = (v >> 16) & 0xff;
    p[3] = (v >> 24) & 0xff;
    p[4] = (v >> 32) & 0xff;
    p[5] = (v >> 40) & 0xff;
    p[6] = (v >> 48) & 0xff;
    p[7] = (v >> 56) & 0xff;
}
#else
#define U64TO8(p, v) ((*reinterpret_cast<unsigned long long*>(p)) = (v))
#endif

static inline void poly1305_init(poly1305_context* ctx, const unsigned char key[32])
{
    poly1305_state_internal_t* st = (poly1305_state_internal_t*)ctx;
    unsigned long long t0, t1;

    /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
    t0 = U8TO64(&key[0]);
    t1 = U8TO64(&key[8]);

    st->r[0] = (t0) & 0xffc0fffffff;
    st->r[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffff;
    st->r[2] = ((t1 >> 24)) & 0x00ffffffc0f;

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

    /* save pad for later */
    st->pad[0] = U8TO64(&key[16]);
    st->pad[1] = U8TO64(&key[24]);

    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 long hibit = (st->final) ? 0 : ((unsigned long long)1 << 40); /* 1 << 128 */
    unsigned long long r0, r1, r2;
    unsigned long long s1, s2;
    unsigned long long h0, h1, h2;
    unsigned long long c;
    uint128_t d0, d1, d2, d;

    r0 = st->r[0];
    r1 = st->r[1];
    r2 = st->r[2];

    h0 = st->h[0];
    h1 = st->h[1];
    h2 = st->h[2];

    s1 = r1 * (5 << 2);
    s2 = r2 * (5 << 2);

    while (bytes >= poly1305_block_size) {
        unsigned long long t0, t1;

        /* h += m[i] */
        t0 = U8TO64(&m[0]);
        t1 = U8TO64(&m[8]);

        h0 += ((t0) & 0xfffffffffff);
        h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff);
        h2 += (((t1 >> 24)) & 0x3ffffffffff) | hibit;

        /* h *= r */
        MUL(d0, h0, r0);
        MUL(d, h1, s2);
        ADD(d0, d);
        MUL(d, h2, s1);
        ADD(d0, d);
        MUL(d1, h0, r1);
        MUL(d, h1, r0);
        ADD(d1, d);
        MUL(d, h2, s2);
        ADD(d1, d);
        MUL(d2, h0, r2);
        MUL(d, h1, r1);
        ADD(d2, d);
        MUL(d, h2, r0);
        ADD(d2, d);

        /* (partial) h %= p */
        c = SHR(d0, 44);
        h0 = LO(d0) & 0xfffffffffff;
        ADDLO(d1, c);
        c = SHR(d1, 44);
        h1 = LO(d1) & 0xfffffffffff;
        ADDLO(d2, c);
        c = SHR(d2, 42);
        h2 = LO(d2) & 0x3ffffffffff;
        h0 += c * 5;
        c = (h0 >> 44);
        h0 = h0 & 0xfffffffffff;
        h1 += c;

        m += poly1305_block_size;
        bytes -= poly1305_block_size;
    }

    st->h[0] = h0;
    st->h[1] = h1;
    st->h[2] = h2;
}

static inline void poly1305_finish(poly1305_context* ctx, unsigned char mac[16])
{
    poly1305_state_internal_t* st = (poly1305_state_internal_t*)ctx;
    unsigned long long h0, h1, h2, c;
    unsigned long long g0, g1, g2;
    unsigned long long t0, t1;

    /* process the remaining block */
    if (st->leftover) {
        size_t i = st->leftover;
        st->buffer[i] = 1;
        for (i = i + 1; 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];

    c = (h1 >> 44);
    h1 &= 0xfffffffffff;
    h2 += c;
    c = (h2 >> 42);
    h2 &= 0x3ffffffffff;
    h0 += c * 5;
    c = (h0 >> 44);
    h0 &= 0xfffffffffff;
    h1 += c;
    c = (h1 >> 44);
    h1 &= 0xfffffffffff;
    h2 += c;
    c = (h2 >> 42);
    h2 &= 0x3ffffffffff;
    h0 += c * 5;
    c = (h0 >> 44);
    h0 &= 0xfffffffffff;
    h1 += c;

    /* compute h + -p */
    g0 = h0 + 5;
    c = (g0 >> 44);
    g0 &= 0xfffffffffff;
    g1 = h1 + c;
    c = (g1 >> 44);
    g1 &= 0xfffffffffff;
    g2 = h2 + c - ((unsigned long long)1 << 42);

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

    /* h = (h + pad) */
    t0 = st->pad[0];
    t1 = st->pad[1];

    h0 += ((t0) & 0xfffffffffff);
    c = (h0 >> 44);
    h0 &= 0xfffffffffff;
    h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff) + c;
    c = (h1 >> 44);
    h1 &= 0xfffffffffff;
    h2 += (((t1 >> 24)) & 0x3ffffffffff) + c;
    h2 &= 0x3ffffffffff;

    /* mac = h % (2^128) */
    h0 = ((h0) | (h1 << 44));
    h1 = ((h1 >> 20) | (h2 << 24));

    U64TO8(&mac[0], h0);
    U64TO8(&mac[8], h1);

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

//////////////////////////////////////////////////////////////////////////////

#else

//////////////////////////////////////////////////////////////////////////////
// More portable 64-bit implementation

#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_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;
}

//////////////////////////////////////////////////////////////////////////////

#endif   // MSC/GCC or not

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;
    }
}

}   // anonymous namespace

void Poly1305::compute(void* auth, const void* data, unsigned int len, const void* key)
{
    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