favela-web / web / static / vendor / sha256-pure.js

/**
 * Pure-JS SHA-256 — public domain implementation.
 * Used as a fallback when crypto.subtle is unavailable (plain HTTP).
 *
 * Input: Uint8Array
 * Output: Uint8Array (32 bytes)
 *
 * Adapted from the well-known compact SHA-256 reference (FIPS 180-4).
 */

export function sha256 (bytes) {
  // Initial hash values (FIPS 180-4 §5.3.3)
  const H = new Uint32Array([
    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
    0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
  ])

  // Round constants (FIPS 180-4 §4.2.2)
  const K = new Uint32Array([
    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
  ])

  // 1. Pad the message (FIPS 180-4 §5.1.1): append 0x80, zero-pad, append 64-bit BE length.
  const bitLen = bytes.length * 8
  // k such that (L + 1 + k) ≡ 448 (mod 512) where L = bytes.length * 8
  const padded = new Uint8Array(Math.ceil((bytes.length + 9) / 64) * 64)
  padded.set(bytes, 0)
  padded[bytes.length] = 0x80
  // 64-bit BE length in the last 8 bytes
  const dv = new DataView(padded.buffer)
  // JS numbers can't hold 64 bits exactly for big inputs, but for our
  // sub-4GB inputs we can set hi=0 and lo=bitLen directly.
  dv.setUint32(padded.length - 8, Math.floor(bitLen / 0x100000000), false)
  dv.setUint32(padded.length - 4, bitLen >>> 0, false)

  // 2. Process each 512-bit (64-byte) chunk.
  const W = new Uint32Array(64)
  for (let chunk = 0; chunk < padded.length; chunk += 64) {
    for (let i = 0; i < 16; i++) {
      W[i] = dv.getUint32(chunk + i * 4, false)
    }
    for (let i = 16; i < 64; i++) {
      const s0 = rotr(W[i - 15], 7) ^ rotr(W[i - 15], 18) ^ (W[i - 15] >>> 3)
      const s1 = rotr(W[i - 2], 17) ^ rotr(W[i - 2], 19) ^ (W[i - 2] >>> 10)
      W[i] = (W[i - 16] + s0 + W[i - 7] + s1) >>> 0
    }

    let a = H[0], b = H[1], c = H[2], d = H[3]
    let e = H[4], f = H[5], g = H[6], h = H[7]

    for (let i = 0; i < 64; i++) {
      const S1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25)
      const ch = (e & f) ^ (~e & g)
      const t1 = (h + S1 + ch + K[i] + W[i]) >>> 0
      const S0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22)
      const maj = (a & b) ^ (a & c) ^ (b & c)
      const t2 = (S0 + maj) >>> 0

      h = g
      g = f
      f = e
      e = (d + t1) >>> 0
      d = c
      c = b
      b = a
      a = (t1 + t2) >>> 0
    }

    H[0] = (H[0] + a) >>> 0
    H[1] = (H[1] + b) >>> 0
    H[2] = (H[2] + c) >>> 0
    H[3] = (H[3] + d) >>> 0
    H[4] = (H[4] + e) >>> 0
    H[5] = (H[5] + f) >>> 0
    H[6] = (H[6] + g) >>> 0
    H[7] = (H[7] + h) >>> 0
  }

  // 3. Emit 32-byte big-endian digest.
  const out = new Uint8Array(32)
  const outDv = new DataView(out.buffer)
  for (let i = 0; i < 8; i++) outDv.setUint32(i * 4, H[i], false)
  return out
}

function rotr (x, n) {
  return ((x >>> n) | (x << (32 - n))) >>> 0
}