初始化

node_modules/undici/lib/web/subresource-integrity/subresource-integrity.js

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+'use strict'
+
+const assert = require('node:assert')
+
+/**
+ * @typedef {object} Metadata
+ * @property {SRIHashAlgorithm} alg - The algorithm used for the hash.
+ * @property {string} val - The base64-encoded hash value.
+ */
+
+/**
+ * @typedef {Metadata[]} MetadataList
+ */
+
+/**
+ * @typedef {('sha256' | 'sha384' | 'sha512')} SRIHashAlgorithm
+ */
+
+/**
+ * @type {Map<SRIHashAlgorithm, number>}
+ *
+ * The valid SRI hash algorithm token set is the ordered set « "sha256",
+ * "sha384", "sha512" » (corresponding to SHA-256, SHA-384, and SHA-512
+ * respectively). The ordering of this set is meaningful, with stronger
+ * algorithms appearing later in the set.
+ *
+ * @see https://w3c.github.io/webappsec-subresource-integrity/#valid-sri-hash-algorithm-token-set
+ */
+const validSRIHashAlgorithmTokenSet = new Map([['sha256', 0], ['sha384', 1], ['sha512', 2]])
+
+// https://nodejs.org/api/crypto.html#determining-if-crypto-support-is-unavailable
+/** @type {import('crypto')} */
+let crypto
+try {
+  crypto = require('node:crypto')
+  const cryptoHashes = crypto.getHashes()
+
+  // If no hashes are available, we cannot support SRI.
+  if (cryptoHashes.length === 0) {
+    validSRIHashAlgorithmTokenSet.clear()
+  }
+
+  for (const algorithm of validSRIHashAlgorithmTokenSet.keys()) {
+    // If the algorithm is not supported, remove it from the list.
+    if (cryptoHashes.includes(algorithm) === false) {
+      validSRIHashAlgorithmTokenSet.delete(algorithm)
+    }
+  }
+  /* c8 ignore next 4 */
+} catch {
+  // If crypto is not available, we cannot support SRI.
+  validSRIHashAlgorithmTokenSet.clear()
+}
+
+/**
+ * @typedef GetSRIHashAlgorithmIndex
+ * @type {(algorithm: SRIHashAlgorithm) => number}
+ * @param {SRIHashAlgorithm} algorithm
+ * @returns {number} The index of the algorithm in the valid SRI hash algorithm
+ * token set.
+ */
+
+const getSRIHashAlgorithmIndex = /** @type {GetSRIHashAlgorithmIndex} */ (Map.prototype.get.bind(
+  validSRIHashAlgorithmTokenSet))
+
+/**
+ * @typedef IsValidSRIHashAlgorithm
+ * @type {(algorithm: string) => algorithm is SRIHashAlgorithm}
+ * @param {*} algorithm
+ * @returns {algorithm is SRIHashAlgorithm}
+ */
+
+const isValidSRIHashAlgorithm = /** @type {IsValidSRIHashAlgorithm} */ (
+  Map.prototype.has.bind(validSRIHashAlgorithmTokenSet)
+)
+
+/**
+ * @param {Uint8Array} bytes
+ * @param {string} metadataList
+ * @returns {boolean}
+ *
+ * @see https://w3c.github.io/webappsec-subresource-integrity/#does-response-match-metadatalist
+ */
+const bytesMatch = crypto === undefined || validSRIHashAlgorithmTokenSet.size === 0
+  // If node is not built with OpenSSL support, we cannot check
+  // a request's integrity, so allow it by default (the spec will
+  // allow requests if an invalid hash is given, as precedence).
+  ? () => true
+  : (bytes, metadataList) => {
+    // 1. Let parsedMetadata be the result of parsing metadataList.
+      const parsedMetadata = parseMetadata(metadataList)
+
+      // 2. If parsedMetadata is empty set, return true.
+      if (parsedMetadata.length === 0) {
+        return true
+      }
+
+      // 3. Let metadata be the result of getting the strongest
+      //    metadata from parsedMetadata.
+      const metadata = getStrongestMetadata(parsedMetadata)
+
+      // 4. For each item in metadata:
+      for (const item of metadata) {
+      // 1. Let algorithm be the item["alg"].
+        const algorithm = item.alg
+
+        // 2. Let expectedValue be the item["val"].
+        const expectedValue = item.val
+
+        // See https://github.com/web-platform-tests/wpt/commit/e4c5cc7a5e48093220528dfdd1c4012dc3837a0e
+        // "be liberal with padding". This is annoying, and it's not even in the spec.
+
+        // 3. Let actualValue be the result of applying algorithm to bytes .
+        const actualValue = applyAlgorithmToBytes(algorithm, bytes)
+
+        // 4. If actualValue is a case-sensitive match for expectedValue,
+        //    return true.
+        if (caseSensitiveMatch(actualValue, expectedValue)) {
+          return true
+        }
+      }
+
+      // 5. Return false.
+      return false
+    }
+
+/**
+ * @param {MetadataList} metadataList
+ * @returns {MetadataList} The strongest hash algorithm from the metadata list.
+ */
+function getStrongestMetadata (metadataList) {
+  // 1. Let result be the empty set and strongest be the empty string.
+  const result = []
+  /** @type {Metadata|null} */
+  let strongest = null
+
+  // 2. For each item in set:
+  for (const item of metadataList) {
+    // 1. Assert: item["alg"] is a valid SRI hash algorithm token.
+    assert(isValidSRIHashAlgorithm(item.alg), 'Invalid SRI hash algorithm token')
+
+    // 2. If result is the empty set, then:
+    if (result.length === 0) {
+      // 1. Append item to result.
+      result.push(item)
+
+      // 2. Set strongest to item.
+      strongest = item
+
+      // 3. Continue.
+      continue
+    }
+
+    // 3. Let currentAlgorithm be strongest["alg"], and currentAlgorithmIndex be
+    // the index of currentAlgorithm in the valid SRI hash algorithm token set.
+    const currentAlgorithm = /** @type {Metadata} */ (strongest).alg
+    const currentAlgorithmIndex = getSRIHashAlgorithmIndex(currentAlgorithm)
+
+    // 4. Let newAlgorithm be the item["alg"], and newAlgorithmIndex be the
+    // index of newAlgorithm in the valid SRI hash algorithm token set.
+    const newAlgorithm = item.alg
+    const newAlgorithmIndex = getSRIHashAlgorithmIndex(newAlgorithm)
+
+    // 5. If newAlgorithmIndex is less than currentAlgorithmIndex, then continue.
+    if (newAlgorithmIndex < currentAlgorithmIndex) {
+      continue
+
+    // 6. Otherwise, if newAlgorithmIndex is greater than
+    // currentAlgorithmIndex:
+    } else if (newAlgorithmIndex > currentAlgorithmIndex) {
+      // 1. Set strongest to item.
+      strongest = item
+
+      // 2. Set result to « item ».
+      result[0] = item
+      result.length = 1
+
+    // 7. Otherwise, newAlgorithmIndex and currentAlgorithmIndex are the same
+    // value. Append item to result.
+    } else {
+      result.push(item)
+    }
+  }
+
+  // 3. Return result.
+  return result
+}
+
+/**
+ * @param {string} metadata
+ * @returns {MetadataList}
+ *
+ * @see https://w3c.github.io/webappsec-subresource-integrity/#parse-metadata
+ */
+function parseMetadata (metadata) {
+  // 1. Let result be the empty set.
+  /** @type {MetadataList} */
+  const result = []
+
+  // 2. For each item returned by splitting metadata on spaces:
+  for (const item of metadata.split(' ')) {
+    // 1. Let expression-and-options be the result of splitting item on U+003F (?).
+    const expressionAndOptions = item.split('?', 1)
+
+    // 2. Let algorithm-expression be expression-and-options[0].
+    const algorithmExpression = expressionAndOptions[0]
+
+    // 3. Let base64-value be the empty string.
+    let base64Value = ''
+
+    // 4. Let algorithm-and-value be the result of splitting algorithm-expression on U+002D (-).
+    const algorithmAndValue = [algorithmExpression.slice(0, 6), algorithmExpression.slice(7)]
+
+    // 5. Let algorithm be algorithm-and-value[0].
+    const algorithm = algorithmAndValue[0]
+
+    // 6. If algorithm is not a valid SRI hash algorithm token, then continue.
+    if (!isValidSRIHashAlgorithm(algorithm)) {
+      continue
+    }
+
+    // 7. If algorithm-and-value[1] exists, set base64-value to
+    // algorithm-and-value[1].
+    if (algorithmAndValue[1]) {
+      base64Value = algorithmAndValue[1]
+    }
+
+    // 8. Let metadata be the ordered map
+    // «["alg" → algorithm, "val" → base64-value]».
+    const metadata = {
+      alg: algorithm,
+      val: base64Value
+    }
+
+    // 9. Append metadata to result.
+    result.push(metadata)
+  }
+
+  // 3. Return result.
+  return result
+}
+
+/**
+ * Applies the specified hash algorithm to the given bytes
+ *
+ * @typedef {(algorithm: SRIHashAlgorithm, bytes: Uint8Array) => string} ApplyAlgorithmToBytes
+ * @param {SRIHashAlgorithm} algorithm
+ * @param {Uint8Array} bytes
+ * @returns {string}
+ */
+const applyAlgorithmToBytes = (algorithm, bytes) => {
+  return crypto.hash(algorithm, bytes, 'base64')
+}
+
+/**
+ * Compares two base64 strings, allowing for base64url
+ * in the second string.
+ *
+ * @param {string} actualValue base64 encoded string
+ * @param {string} expectedValue base64 or base64url encoded string
+ * @returns {boolean}
+ */
+function caseSensitiveMatch (actualValue, expectedValue) {
+  // Ignore padding characters from the end of the strings by
+  // decreasing the length by 1 or 2 if the last characters are `=`.
+  let actualValueLength = actualValue.length
+  if (actualValueLength !== 0 && actualValue[actualValueLength - 1] === '=') {
+    actualValueLength -= 1
+  }
+  if (actualValueLength !== 0 && actualValue[actualValueLength - 1] === '=') {
+    actualValueLength -= 1
+  }
+  let expectedValueLength = expectedValue.length
+  if (expectedValueLength !== 0 && expectedValue[expectedValueLength - 1] === '=') {
+    expectedValueLength -= 1
+  }
+  if (expectedValueLength !== 0 && expectedValue[expectedValueLength - 1] === '=') {
+    expectedValueLength -= 1
+  }
+
+  if (actualValueLength !== expectedValueLength) {
+    return false
+  }
+
+  for (let i = 0; i < actualValueLength; ++i) {
+    if (
+      actualValue[i] === expectedValue[i] ||
+      (actualValue[i] === '+' && expectedValue[i] === '-') ||
+      (actualValue[i] === '/' && expectedValue[i] === '_')
+    ) {
+      continue
+    }
+    return false
+  }
+
+  return true
+}
+
+module.exports = {
+  applyAlgorithmToBytes,
+  bytesMatch,
+  caseSensitiveMatch,
+  isValidSRIHashAlgorithm,
+  getStrongestMetadata,
+  parseMetadata
+}