check for unknown digest

Author: ddebin

src/lib/decrypt_transform.ts

@@ -5,20 +5,20 @@ export class DecryptTransform extends Transform {
   private decipher?: crypto.Decipher
   private algo: string
   private cipherKey: crypto.KeyObject
-  private cipherIvLength: number
+  private ivLength: number
   private inputEncoding?: BufferEncoding
 
   constructor(
     algo: string,
     cipherKey: crypto.KeyObject,
-    cipherIvLength: number,
+    ivLength: number,
     inputEncoding?: BufferEncoding,
     opts?: TransformOptions,
   ) {
     super(opts)
     this.algo = algo
     this.cipherKey = cipherKey
-    this.cipherIvLength = cipherIvLength
+    this.ivLength = ivLength
     this.inputEncoding = inputEncoding
   }
 
@@ -30,9 +30,9 @@ export class DecryptTransform extends Transform {
     if (!this.decipher) {
       // Unpackage the combined iv + encrypted message.
       // Since we are using a fixed size IV, we can hard code the slice length.
-      const iv = data.subarray(0, this.cipherIvLength)
+      const iv = data.subarray(0, this.ivLength)
       this.decipher = crypto.createDecipheriv(this.algo, this.cipherKey, iv)
-      data = data.subarray(this.cipherIvLength)
+      data = data.subarray(this.ivLength)
     }
     this.push(this.decipher.update(data))
     callback()

src/lib/ssh_agent_client.ts

@@ -74,13 +74,13 @@ export class SSHAgentClient {
 
   /**
    * @param options - Optional configuration.
-   * @throws {Error} if SSH_AUTH_SOCK is not set.
+   * @throws {Error} if SSH_AUTH_SOCK is not set or socket not found.
    */
   constructor(options: SSHAgentClientOptions = {}) {
     /** Socket operation timeout in milliseconds (default: 10000) */
     this.timeout = options.timeout ?? 10000
 
-    /** Encryption and algo key length must match */
+    /** Digest and cipher key length must match */
     this.cipherAlgo = options.cipherAlgo ?? 'aes-256-cbc'
     this.digestAlgo = options.digestAlgo ?? 'sha256'
 
@@ -180,6 +180,12 @@ export class SSHAgentClient {
     return this.request(buildRequest, parseResponse, Protocol.SSH2_AGENT_SIGN_RESPONSE)
   }
 
+  /**
+   * Encrypt data with given `SSHKey` and `seed` string, using SSH signature as the encryption key.
+   *
+   * Resolves with a string containing the IV and encrypted data, encoded in `outputEncoding` (default: "hex").
+   * The IV is needed for decryption and is included in the output as a prefix to the encrypted data.
+   */
   async encrypt(
     key: SSHKey,
     seed: string,
@@ -192,6 +198,13 @@ export class SSHAgentClient {
     )
   }
 
+  /**
+   * Get a Transform stream that encrypts data with given `SSHKey` and `seed` string, using SSH signature as
+   * the encryption key.
+   *
+   * The Transform stream outputs plain binary or a string encoded in `outputEncoding`.
+   * The IV is needed for decryption and is included in the output as a prefix to the encrypted data.
+   */
   async getEncryptTransform(
     key: SSHKey,
     seed: string,
@@ -206,6 +219,12 @@ export class SSHAgentClient {
     })
   }
 
+  /**
+   * Decrypt data with given `SSHKey` and `seed` string, using SSH signature as the decryption key.
+   *
+   * Resolves with a Buffer containing the decrypted data.
+   * The IV is needed for decryption and should be included in the input as a prefix to the encrypted data.
+   */
   async decrypt(
     key: SSHKey,
     seed: string,
@@ -223,6 +242,14 @@ export class SSHAgentClient {
     })
   }
 
+  /**
+   * Get a Transform stream that decrypts data with given `SSHKey` and `seed` string, using SSH signature as
+   * the decryption key.
+   *
+   * The Transform stream expects encrypted data (as plain binary or a string encoded in `inputEncoding`) and
+   * outputs a Buffer containing the decrypted data.
+   * The IV is needed for decryption and should be included in the input as a prefix to the encrypted data.
+   */
   async getDecryptTransform(
     key: SSHKey,
     seed: string,
@@ -252,14 +279,17 @@ export class SSHAgentClient {
     return this.sign(key, Buffer.from(seed, 'utf8')).then(signature => {
       const cipherInfo = crypto.getCipherInfo(this.cipherAlgo)
       if (!cipherInfo?.ivLength) {
-        throw new Error('Wrong cipher algo')
+        throw new Error('Unknown symmetric cipher algo')
+      }
+      if (!crypto.getHashes().includes(this.digestAlgo)) {
+        throw new Error('Unknown digest algo')
       }
-      const hash = crypto.createHash(this.digestAlgo).update(signature.raw).digest()
-      if (hash.length < cipherInfo.keyLength) {
-        throw new Error("Digest algo doesn't match cipher key length")
+      const digest = crypto.createHash(this.digestAlgo).update(signature.raw).digest()
+      if (digest.length < cipherInfo.keyLength) {
+        throw new Error("Digest length doesn't match cipher key length")
       }
       return {
-        cipherKey: crypto.createSecretKey(hash.subarray(0, cipherInfo.keyLength)),
+        cipherKey: crypto.createSecretKey(digest.subarray(0, cipherInfo.keyLength)),
         ivLength: cipherInfo.ivLength,
       }
     })

test/ssh_agent_client.spec.ts

@@ -102,15 +102,15 @@ describe('SSHAgentClient tests', () => {
       .expect(agent.decrypt(identity, SEED, data))
       .to.be.rejectedWith(Error, 'error:1C80006B:Provider routines::wrong final block length')
   })
-  it('should throw if unknown cipher', async () => {
+  it('should throw if cipher algorithm is unknown', async () => {
     const agent = new SSHAgentClient({ cipherAlgo: 'xxx' })
     const identity = await agent.getIdentity('key_rsa')
     if (!identity) {
       throw new Error()
     }
     return chai
       .expect(agent.encrypt(identity, SEED, DECODED_STRING_BUFFER))
-      .to.be.rejectedWith(Error, 'Wrong cipher algo')
+      .to.be.rejectedWith(Error, 'Unknown symmetric cipher algo')
   })
   it('should throw if digest length is less than cipher key length', async () => {
     const agent = new SSHAgentClient({ cipherAlgo: 'aes-192-cbc', digestAlgo: 'sha1' })
@@ -120,7 +120,17 @@ describe('SSHAgentClient tests', () => {
     }
     return chai
       .expect(agent.encrypt(identity, SEED, DECODED_STRING_BUFFER))
-      .to.be.rejectedWith(Error, "Digest algo doesn't match cipher key length")
+      .to.be.rejectedWith(Error, "Digest length doesn't match cipher key length")
+  })
+  it('should throw if hash algorithm is unknown', async () => {
+    const agent = new SSHAgentClient({ digestAlgo: 'xxx' })
+    const identity = await agent.getIdentity('key_rsa')
+    if (!identity) {
+      throw new Error()
+    }
+    return chai
+      .expect(agent.encrypt(identity, SEED, DECODED_STRING_BUFFER))
+      .to.be.rejectedWith(Error, 'Unknown digest algo')
   })
 })