feat: add sha256 algorithm

2 files changed, 175 insertions, 0 deletions

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;
+    }
+}