crypto: adjust minimum length in generateKey('hmac', ...)

Also affects generateKeySync('hmac', ...)

PR-URL: #42944
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/crypto.md

@@ -3584,7 +3584,7 @@ added: v15.0.0
 * `options`: {Object}
   * `length`: {number} The bit length of the key to generate. This must be a
     value greater than 0.
-    * If `type` is `'hmac'`, the minimum is 1, and the maximum length is
+    * If `type` is `'hmac'`, the minimum is 8, and the maximum length is
       2<sup>31</sup>-1. If the value is not a multiple of 8, the generated
       key will be truncated to `Math.floor(length / 8)`.
     * If `type` is `'aes'`, the length must be one of `128`, `192`, or `256`.
@@ -3851,7 +3851,7 @@ added: v15.0.0
   accepted values are `'hmac'` and `'aes'`.
 * `options`: {Object}
   * `length`: {number} The bit length of the key to generate.
-    * If `type` is `'hmac'`, the minimum is 1, and the maximum length is
+    * If `type` is `'hmac'`, the minimum is 8, and the maximum length is
       2<sup>31</sup>-1. If the value is not a multiple of 8, the generated
       key will be truncated to `Math.floor(length / 8)`.
     * If `type` is `'aes'`, the length must be one of `128`, `192`, or `256`.

lib/internal/crypto/keygen.js

@@ -356,7 +356,7 @@ function generateKeyJob(mode, keyType, options) {
   const { length } = options;
   switch (keyType) {
     case 'hmac':
-      validateInteger(length, 'options.length', 1, 2 ** 31 - 1);
+      validateInteger(length, 'options.length', 8, 2 ** 31 - 1);
       break;
     case 'aes':
       validateOneOf(length, 'options.length', kAesKeyLengths);

test/parallel/test-crypto-secret-keygen.js

@@ -51,6 +51,14 @@ assert.throws(() => generateKey('hmac', { length: -1 }, common.mustNotCall()), {
   code: 'ERR_OUT_OF_RANGE'
 });
 
+assert.throws(() => generateKey('hmac', { length: 4 }, common.mustNotCall()), {
+  code: 'ERR_OUT_OF_RANGE'
+});
+
+assert.throws(() => generateKey('hmac', { length: 7 }, common.mustNotCall()), {
+  code: 'ERR_OUT_OF_RANGE'
+});
+
 assert.throws(
   () => generateKey('hmac', { length: 2 ** 31 }, common.mustNotCall()), {
     code: 'ERR_OUT_OF_RANGE'
@@ -60,6 +68,14 @@ assert.throws(() => generateKeySync('hmac', { length: -1 }), {
   code: 'ERR_OUT_OF_RANGE'
 });
 
+assert.throws(() => generateKeySync('hmac', { length: 4 }), {
+  code: 'ERR_OUT_OF_RANGE'
+});
+
+assert.throws(() => generateKeySync('hmac', { length: 7 }), {
+  code: 'ERR_OUT_OF_RANGE'
+});
+
 assert.throws(
   () => generateKeySync('hmac', { length: 2 ** 31 }), {
     code: 'ERR_OUT_OF_RANGE'