移动端crypto.subtle.digest报错咨询：兼容问题与原生替代方案

是否属于移动端浏览器兼容性问题？ #

并非单纯的兼容性问题，核心是iOS平台的浏览器安全限制：

• 现代桌面浏览器允许在localhost或局域网IP的HTTP环境下使用crypto.subtle API，但iOS上的Safari及基于其内核的Chrome（iOS所有第三方浏览器都强制使用Safari内核），会在非HTTPS环境下完全禁用crypto.subtle，这才导致你出现undefined is not an object (evaluating 'crypto.subtle.digest')的错误。

无需外部库的移动端Chrome原生替代方案 #

因为iOS Chrome依赖Safari内核，无法绕过crypto.subtle的HTTP禁用限制，所以只能通过纯JavaScript手写SHA256算法实现替代，不依赖浏览器的Web Crypto API。以下是一个兼容多环境的极简实现：

function sha256(str) {
  const buffer = new TextEncoder().encode(str);
  // 优先使用浏览器原生API（HTTPS环境下）
  if (crypto.subtle) {
    return crypto.subtle.digest('SHA-256', buffer).then(hash => {
      return Array.from(new Uint8Array(hash))
        .map(b => b.toString(16).padStart(2, '0'))
        .join('');
    });
  }
  // HTTP环境下的纯JS SHA256实现
  return (async function() {
    function rotateRight(n, b) { return (n >>> b) | (n << (32 - b)); }
    function safeAdd(x, y) { 
      let lsw = (x & 0xFFFF) + (y & 0xFFFF);
      let msw = (x >> 16) + (y >> 16) + (lsw >> 16);
      return (msw << 16) | (lsw & 0xFFFF);
    }
    const 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];
    const message = new Uint8Array(buffer);
    const len = message.length;
    const blockCount = Math.ceil((len + 9) / 64);
    const blocks = new Uint32Array(blockCount * 16);
    
    for (let i = 0; i < len; i++) {
      blocks[i >> 2] |= message[i] << (24 - (i % 4) * 8);
    }
    blocks[len >> 2] |= 0x80 << (24 - (len % 4) * 8);
    blocks[blockCount * 16 - 2] = len * 8;

    let h0 = 0x6a09e667, h1 = 0xbb67ae85, h2 = 0x3c6ef372, h3 = 0xa54ff53a;
    let h4 = 0x510e527f, h5 = 0x9b05688c, h6 = 0x1f83d9ab, h7 = 0x5be0cd19;

    for (let i = 0; i < blockCount; i++) {
      const w = new Uint32Array(64);
      for (let j = 0; j < 16; j++) w[j] = blocks[i * 16 + j];
      for (let j = 16; j < 64; j++) {
        const s0 = rotateRight(w[j-15], 7) ^ rotateRight(w[j-15], 18) ^ (w[j-15] >>> 3);
        const s1 = rotateRight(w[j-2], 17) ^ rotateRight(w[j-2], 19) ^ (w[j-2] >>> 10);
        w[j] = safeAdd(safeAdd(safeAdd(w[j-16], s0), w[j-7]), s1);
      }
      let a = h0, b = h1, c = h2, d = h3, e = h4, f = h5, g = h6, h = h7;
      for (let j = 0; j < 64; j++) {
        const S1 = rotateRight(e, 6) ^ rotateRight(e, 11) ^ rotateRight(e, 25);
        const ch = (e & f) ^ (~e & g);
        const temp1 = safeAdd(safeAdd(safeAdd(safeAdd(h, S1), ch), K[j]), w[j]);
        const S0 = rotateRight(a, 2) ^ rotateRight(a, 13) ^ rotateRight(a, 22);
        const maj = (a & b) ^ (a & c) ^ (b & c);
        const temp2 = safeAdd(S0, maj);
        h = g; g = f; f = e; e = safeAdd(d, temp1); d = c; c = b; b = a; a = safeAdd(temp1, temp2);
      }
      h0 = safeAdd(h0, a); h1 = safeAdd(h1, b); h2 = safeAdd(h2, c); h3 = safeAdd(h3, d);
      h4 = safeAdd(h4, e); h5 = safeAdd(h5, f); h6 = safeAdd(h6, g); h7 = safeAdd(h7, h);
    }
    const hashArray = [h0, h1, h2, h3, h4, h5, h6, h7].map(x => {
      const hex = x.toString(16);
      return hex.length === 8 ? hex : '0'.repeat(8 - hex.length) + hex;
    });
    return hashArray.join('').toLowerCase();
  })();
}

// 使用示例
sha256('test').then(hash => console.log(hash));

该实现会自动判断环境：HTTPS下优先用高效的原生API，HTTP环境下 fallback 到纯JS算法，兼容iOS移动端场景。

关于obs-web在移动端HTTP环境正常运行的原因 #

obs-web没有依赖浏览器的crypto.subtle API，而是自行实现了纯JavaScript的加密逻辑，因此不受iOS平台对crypto.subtle的HTTP限制，能在移动端HTTP环境下正常工作。

内容的提问来源于stack exchange，提问作者CodeCamper