text: /* 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 <esp8266.h>
  #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
  //#define SHA_BIG_ENDIAN
  
  
  
  /* code */
  #define SHA1_K0  0x5a827999
  #define SHA1_K20 0x6ed9eba1
  #define SHA1_K40 0x8f1bbcdc
  #define SHA1_K60 0xca62c1d6
  
  void ICACHE_FLASH_ATTR sha1_init(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;
  }
  
  uint32_t ICACHE_FLASH_ATTR sha1_rol32(uint32_t number, uint8_t bits) {
  	return ((number << bits) | (number >> (32-bits)));
  }
  
  void ICACHE_FLASH_ATTR sha1_hashBlock(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;
  }
  
  void ICACHE_FLASH_ATTR sha1_addUncounted(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 ICACHE_FLASH_ATTR sha1_writebyte(sha1nfo *s, uint8_t data) {
  	++s->byteCount;
  	sha1_addUncounted(s, data);
  }
  
  void ICACHE_FLASH_ATTR sha1_write(sha1nfo *s, const char *data, size_t len) {
  	for (;len--;) sha1_writebyte(s, (uint8_t) *data++);
  }
  
  void ICACHE_FLASH_ATTR sha1_pad(sha1nfo *s) {
  	// Implement SHA-1 padding (fips180-2 Â§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* ICACHE_FLASH_ATTR sha1_result(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 ICACHE_FLASH_ATTR sha1_initHmac(sha1nfo *s, const uint8_t* key, int keyLength) {
  	uint8_t i;
  	memset(s->keyBuffer, 0, BLOCK_LENGTH);
  	if (keyLength > BLOCK_LENGTH) {
  		// Hash long keys
  		sha1_init(s);
  		for (;keyLength--;) sha1_writebyte(s, *key++);
  		memcpy(s->keyBuffer, sha1_result(s), HASH_LENGTH);
  	} else {
  		// Block length keys are used as is
  		memcpy(s->keyBuffer, key, keyLength);
  	}
  	// Start inner hash
  	sha1_init(s);
  	for (i=0; i<BLOCK_LENGTH; i++) {
  		sha1_writebyte(s, s->keyBuffer[i] ^ HMAC_IPAD);
  	}
  }
  
  uint8_t* ICACHE_FLASH_ATTR sha1_resultHmac(sha1nfo *s) {
  	uint8_t i;
  	// Complete inner hash
  	memcpy(s->innerHash,sha1_result(s),HASH_LENGTH);
  	// Calculate outer hash
  	sha1_init(s);
  	for (i=0; i<BLOCK_LENGTH; i++) sha1_writebyte(s, s->keyBuffer[i] ^ HMAC_OPAD);
  	for (i=0; i<HASH_LENGTH; i++) sha1_writebyte(s, s->innerHash[i]);
  	return sha1_result(s);
  }
  