/* This code is public-domain - it is based on libcrypt
 * placed in the public domain by Wei Dai and other contributors.
 */
// gcc -Wall -DSHA1TEST -o sha1test sha1.c && ./sha1test

#include <stdint.h>
#include <string.h>
#include "sha1.h"

//according to http://ip.cadence.com/uploads/pdf/xtensalx_overview_handbook.pdf
// the cpu is normally defined as little ending, but can be big endian too.
// for the esp this seems to work

#if defined(__BYTE_ORDER__)&&(__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
#define SHA_BIG_ENDIAN
#endif

/* code */
#define SHA1_K0  0x5a827999
#define SHA1_K20 0x6ed9eba1
#define SHA1_K40 0x8f1bbcdc
#define SHA1_K60 0xca62c1d6

void httpd_sha1_init(httpd_sha1nfo *s)
{
    s->state[0] = 0x67452301;
    s->state[1] = 0xefcdab89;
    s->state[2] = 0x98badcfe;
    s->state[3] = 0x10325476;
    s->state[4] = 0xc3d2e1f0;
    s->byteCount = 0;
    s->bufferOffset = 0;
}

static uint32_t sha1_rol32(uint32_t number, uint8_t bits)
{
    return ((number << bits) | (number >> (32 - bits)));
}

static void sha1_hashBlock(httpd_sha1nfo *s)
{
    uint8_t i;
    uint32_t a, b, c, d, e, t;

    a = s->state[0];
    b = s->state[1];
    c = s->state[2];
    d = s->state[3];
    e = s->state[4];
    for (i = 0; i < 80; i++) {
        if (i >= 16) {
            t = s->buffer[(i + 13) & 15] ^ s->buffer[(i + 8) & 15] ^ s->buffer[(i + 2) & 15] ^ s->buffer[i & 15];
            s->buffer[i & 15] = sha1_rol32(t, 1);
        }
        if (i < 20) {
            t = (d ^ (b & (c ^ d))) + SHA1_K0;
        } else if (i < 40) {
            t = (b ^ c ^ d) + SHA1_K20;
        } else if (i < 60) {
            t = ((b & c) | (d & (b | c))) + SHA1_K40;
        } else {
            t = (b ^ c ^ d) + SHA1_K60;
        }
        t += sha1_rol32(a, 5) + e + s->buffer[i & 15];
        e = d;
        d = c;
        c = sha1_rol32(b, 30);
        b = a;
        a = t;
    }
    s->state[0] += a;
    s->state[1] += b;
    s->state[2] += c;
    s->state[3] += d;
    s->state[4] += e;
}

static void sha1_addUncounted(httpd_sha1nfo *s, uint8_t data)
{
    uint8_t *const b = (uint8_t *) s->buffer;
#ifdef SHA_BIG_ENDIAN
    b[s->bufferOffset] = data;
#else
    b[s->bufferOffset ^ 3] = data;
#endif
    s->bufferOffset++;
    if (s->bufferOffset == BLOCK_LENGTH) {
        sha1_hashBlock(s);
        s->bufferOffset = 0;
    }
}

void httpd_sha1_writebyte(httpd_sha1nfo *s, uint8_t data)
{
    ++s->byteCount;
    sha1_addUncounted(s, data);
}

void httpd_sha1_write(httpd_sha1nfo *s, const char *data, size_t len)
{
    for (; len--;) { httpd_sha1_writebyte(s, (uint8_t) *data++); }
}

static void sha1_pad(httpd_sha1nfo *s)
{
    // Implement SHA-1 padding (fips180-2 §5.1.1)

    // Pad with 0x80 followed by 0x00 until the end of the block
    sha1_addUncounted(s, 0x80);
    while (s->bufferOffset != 56) { sha1_addUncounted(s, 0x00); }

    // Append length in the last 8 bytes
    sha1_addUncounted(s, 0); // We're only using 32 bit lengths
    sha1_addUncounted(s, 0); // But SHA-1 supports 64 bit lengths
    sha1_addUncounted(s, 0); // So zero pad the top bits
    sha1_addUncounted(s, s->byteCount >> 29); // Shifting to multiply by 8
    sha1_addUncounted(s, s->byteCount >> 21); // as SHA-1 supports bitstreams as well as
    sha1_addUncounted(s, s->byteCount >> 13); // byte.
    sha1_addUncounted(s, s->byteCount >> 5);
    sha1_addUncounted(s, s->byteCount << 3);
}

uint8_t *httpd_sha1_result(httpd_sha1nfo *s)
{
    // Pad to complete the last block
    sha1_pad(s);

#ifndef SHA_BIG_ENDIAN
    // Swap byte order back
    int i;
    for (i = 0; i < 5; i++) {
        s->state[i] =
                (((s->state[i]) << 24) & 0xff000000)
                | (((s->state[i]) << 8) & 0x00ff0000)
                | (((s->state[i]) >> 8) & 0x0000ff00)
                | (((s->state[i]) >> 24) & 0x000000ff);
    }
#endif

    // Return pointer to hash (20 characters)
    return (uint8_t *) s->state;
}

#define HMAC_IPAD 0x36
#define HMAC_OPAD 0x5c

void httpd_sha1_initHmac(httpd_sha1nfo *s, const uint8_t *key, size_t keyLength)
{
    uint8_t i;
    memset(s->keyBuffer, 0, BLOCK_LENGTH);
    if (keyLength > BLOCK_LENGTH) {
        // Hash long keys
        httpd_sha1_init(s);
        for (; keyLength--;) { httpd_sha1_writebyte(s, *key++); }
        memcpy(s->keyBuffer, httpd_sha1_result(s), HASH_LENGTH);
    } else {
        // Block length keys are used as is
        memcpy(s->keyBuffer, key, keyLength);
    }
    // Start inner hash
    httpd_sha1_init(s);
    for (i = 0; i < BLOCK_LENGTH; i++) {
        httpd_sha1_writebyte(s, s->keyBuffer[i] ^ HMAC_IPAD);
    }
}

uint8_t *httpd_sha1_resultHmac(httpd_sha1nfo *s)
{
    uint8_t i;
    // Complete inner hash
    memcpy(s->innerHash, httpd_sha1_result(s), HASH_LENGTH);
    // Calculate outer hash
    httpd_sha1_init(s);
    for (i = 0; i < BLOCK_LENGTH; i++) { httpd_sha1_writebyte(s, s->keyBuffer[i] ^ HMAC_OPAD); }
    for (i = 0; i < HASH_LENGTH; i++) { httpd_sha1_writebyte(s, s->innerHash[i]); }
    return httpd_sha1_result(s);
}