feat: add sha256 algorithm

3 files changed, 278 insertions, 0 deletions

diff --git a/include/sha256.h b/include/sha256.h
new file mode 100644
index 0000000..18fba6a
--- /dev/null
+++ b/include/sha256.h
@@ -0,0 +1,103 @@
+// This file is part of a crypto library, exam for the Algorithms class.
+// All of these files are under MIT license.
+//
+// SHA declaration document:
+// https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf
+
+#ifndef HMACSHA256_SHA256_H_
+#define HMACSHA256_SHA256_H_
+
+#include<cstdint>
+#include<array>
+
+namespace hmacsha256 {
+class SHA256 {
+public:
+    // create a new SHA256 thanks an array of bytes
+    SHA256(const uint8_t*, uint32_t);
+
+    SHA256(const std::string&);
+
+    // get digest as array of bytes
+    uint8_t* digest();
+
+    std::string hexdigest();
+private:
+    uint8_t* digest_;
+
+    // work variables: a, b, c, d, e, f, g, h
+    uint32_t vars_[8];
+
+    // data message, in bytes
+    // M,  "message to be hashed"
+    uint8_t message_[64];
+
+    // length L of the original message
+    uint32_t message_l_;
+
+    // lengh of bits
+    uint64_t bit_len_;
+
+    // first 80 costansts 64bit words, paragraph 4.2.2
+    std::array<uint32_t, 64> K = {
+        0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,
+        0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
+        0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,
+        0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
+        0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,
+        0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
+        0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,
+        0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
+        0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,
+        0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
+        0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,
+        0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
+        0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,
+        0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
+        0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,
+        0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
+    };
+
+    // the constructor
+    void init(const uint8_t* data, uint32_t length);
+
+    // Ch(x, y, z) = (x | y) ^ (~x & z)
+    static uint32_t ch(uint32_t, uint32_t, uint32_t);
+
+    // Maj(x, y, z) = (x | y) ^ (x & z) ^ (y & z)
+    static uint32_t maj(uint32_t, uint32_t, uint32_t);
+
+    // circular right shift. Takes two params: `x` a w-bit word and `n` an int
+    // with 0 <= n < w.
+    // w, in our case is 32
+    //
+    // rots is also defined in the NIST document as 
+    // rotr(x) = (x >> n) or (x << w - n)
+    static uint32_t rotr(uint32_t, uint32_t);
+
+    // function defined in 4.4
+    static uint32_t big_sigma0(uint32_t);
+
+    // function defined in 4.5
+    static uint32_t big_sigma1(uint32_t);
+
+    // function defined in 4.6
+    static uint32_t sigma0(uint32_t);
+
+    // function defined in 4.7
+    static uint32_t sigma1(uint32_t);
+
+    // padding
+    void pad();
+
+    // main function
+    void transform();
+
+    // transform bytes in big-endian, because SHA256 wants big endian ordering
+    // Takes 1 parameter, the array of bytes that we want to reorder
+    void bigendian(uint8_t*);
+};
+
+} // namespace hmacsha256
+
+#endif // HMACSHA256_SHA256_H_
diff --git a/src/main.cc b/src/main.cc
new file mode 100644
index 0000000..9f01c14
--- /dev/null
+++ b/src/main.cc
@@ -0,0 +1,10 @@
+#include<iostream>
+#include "sha256.h"
+
+int main(int argc, char** argv) {
+    auto sha = hmacsha256::SHA256(argv[1]);
+    sha.digest();
+    std::cout << sha.hexdigest();
+
+    return 0;
+}
diff --git a/src/sha256.cc b/src/sha256.cc
new file mode 100644
index 0000000..7790f8a
--- /dev/null
+++ b/src/sha256.cc
@@ -0,0 +1,165 @@
+#include "sha256.h"
+#include<cstring> // used for memset
+#include<sstream> // used for stringstream
+#include<iomanip> // used for setfill and setw
+
+hmacsha256::SHA256::SHA256(const uint8_t* data, uint32_t length) {
+    init(data, length);
+}
+
+void hmacsha256::SHA256::init(const uint8_t* data, uint32_t length) {
+    message_l_ = bit_len_ = 0;
+    vars_[0] = 0x6a09e667;
+    vars_[1] = 0xbb67ae85;
+    vars_[2] = 0x3c6ef372;
+    vars_[3] = 0xa54ff53a;
+    vars_[4] = 0x510e527f;
+    vars_[5] = 0x9b05688c;
+    vars_[6] = 0x1f83d9ab;
+    vars_[7] = 0x5be0cd19;
+
+    for(size_t i = 0; i < length; ++i) {
+        message_[message_l_++] = data[i];
+        if(message_l_ == 64) {
+            transform();
+
+            bit_len_ += 512;
+            message_l_ = 0;
+        }
+    }
+}
+
+hmacsha256::SHA256::SHA256(const std::string& data) {
+    init(reinterpret_cast<const uint8_t*> (data.c_str()), data.size());
+}
+
+uint8_t* hmacsha256::SHA256::digest() {
+    uint8_t* hash = new uint8_t[32];
+
+    pad();
+    bigendian(hash);
+
+    for(uint32_t i = 0; i < 32; ++i) {
+        digest_[i] = hash[i];
+    }
+
+    return hash;
+}
+
+std::string hmacsha256::SHA256::hexdigest() {
+    std::stringstream s;
+    s << std::setfill('0') << std::hex;
+
+    for(uint8_t i = 0 ; i < 32 ; i++) {
+        s << std::setw(2) << (unsigned int) digest_[i];
+    }
+
+    return s.str();
+}
+
+uint32_t hmacsha256::SHA256::ch(uint32_t x, uint32_t y, uint32_t z) {
+    return (x & y) ^ (~x & z);
+}
+
+uint32_t hmacsha256::SHA256::maj(uint32_t x, uint32_t y, uint32_t z) {
+    return (x & (y | z)) | (y & z);
+}
+
+uint32_t hmacsha256::SHA256::rotr(uint32_t x, uint32_t n) {
+    return (x >> n) | (x << (32-n));
+}
+
+uint32_t hmacsha256::SHA256::big_sigma0(uint32_t x) {
+    return SHA256::rotr(x, 2) ^ SHA256::rotr(x, 13) ^ SHA256::rotr(x, 22);
+}
+
+uint32_t hmacsha256::SHA256::big_sigma1(uint32_t x) {
+    return SHA256::rotr(x, 6) ^ SHA256::rotr(x, 11) ^ SHA256::rotr(x, 25);
+}
+
+uint32_t hmacsha256::SHA256::sigma0(uint32_t x) {
+    return SHA256::rotr(x, 7) ^ SHA256::rotr(x, 18) ^ (x >> 3);
+}
+
+uint32_t hmacsha256::SHA256::sigma1(uint32_t x) {
+    return SHA256::rotr(x, 17) ^ SHA256::rotr(x, 19) ^ (x >> 10);
+}
+
+void hmacsha256::SHA256::transform() {
+    uint32_t m[64];
+    uint32_t h[8];
+
+    for(uint8_t i = 0, j = 0; i < 16; ++i, j += 4) {
+        m[i] = (message_[j] << 24) | (message_[j + 1] << 16) | (message_[j + 2] << 8) | (message_[j + 3]);
+    }
+
+    for(uint8_t i = 16; i < 64; ++i) {
+        m[i] = SHA256::sigma1(m[i - 2]) + m[i - 7] + SHA256::sigma0(m[i - 15]) + m[i - 16];
+    }
+
+    for(uint8_t i = 0; i < 8; ++i)
+        h[i] = vars_[i];
+
+    for(uint8_t i = 0; i < 64; ++i) {
+        auto S1 = SHA256::big_sigma1(h[4]);
+        auto S0 = SHA256::big_sigma0(h[0]);
+        auto t1 = h[7] + S1 + SHA256::ch(h[4], h[5], h[6]) + K[i] + m[i];
+        auto t2 = S0 + SHA256::maj(h[0], h[1], h[2]);
+        h[7] = h[6];
+        h[6] = h[5];
+        h[5] = h[4];
+        h[4] = h[3] + t1;
+        h[3] = h[2];
+        h[2] = h[1];
+        h[1] = h[0];
+        h[0] = t1 + t2;
+    }
+
+    for(uint8_t i = 0; i < 8; ++i) {
+        vars_[i]+=h[i];
+    }
+
+}
+
+void hmacsha256::SHA256::pad() {
+    // start of scanning
+    uint64_t i = message_l_;
+
+    // end of scanning
+    uint8_t j = (i < 56) ? 56 : 64;
+
+    // append '1' bit at the end of the block
+    message_[i++] = 0x80;
+
+    // append '0' bit, j times
+    while(i < j) message_[i++] = 0x00;
+
+    if(message_l_ >= 56) {
+        transform();
+        memset(message_, 0, 56);
+    }
+
+    bit_len_ += message_l_ * 8;
+    message_[63] = bit_len_;
+    message_[62] = bit_len_ >> 8;
+    message_[61] = bit_len_ >> 16;
+    message_[60] = bit_len_ >> 24;
+    message_[59] = bit_len_ >> 32;
+    message_[58] = bit_len_ >> 40;
+    message_[57] = bit_len_ >> 48;
+    message_[56] = bit_len_ >> 56;
+    transform();
+}
+
+void hmacsha256::SHA256::bigendian(uint8_t* hash) {
+    for (uint32_t i = 0; i < 4; ++i) {
+        hash[i] = (vars_[0] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 4] = (vars_[1] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 8] = (vars_[2] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 12] = (vars_[3] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 16] = (vars_[4] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 20] = (vars_[5] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 24] = (vars_[6] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 28] = (vars_[7] >> (24 - i * 8)) & 0x000000ff;
+    }
+}