added: SodiumRandomNumberGenerator (jedisct1#255)

* added: SodiumRandomNumberGenerator * fixed: Test * refactored
reincubate · May 27, 2022 · 54d520e · 54d520e
1 parent 862e9ad
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diff --git a/README.md b/README.md
@@ -248,6 +248,16 @@ let seed = "0123456789abcdef0123456789abcdef".bytes
 let stream = sodium.randomBytes.deterministic(length: 1000, seed: seed)!
 ```
 
+Use `RandomBytes.Generator` as a generator to produce cryptographically secure pseudorandom numbers.
+
+```swift
+var rng = RandomBytes.Generator()
+let randomUInt32 = UInt32.random(in: 0...10, using: &rng)
+let randomUInt64 = UInt64.random(in: 0...10, using: &rng)
+let randomInt = Int.random(in: 0...10, using: &rng)
+let randomDouble = Double.random(in: 0...1, using: &rng)
+```
+
 ## Password hashing
 
 Password hashing provides the ability to derive key material from a low-entropy password. Password hashing functions are designed to be expensive to hamper brute force attacks, thus the computational and memory parameters may be user-defined.

diff --git a/Sodium/RandomBytes.swift b/Sodium/RandomBytes.swift
@@ -57,3 +57,21 @@ extension RandomBytes {
         return output
     }
 }
+
+extension RandomBytes {
+    public struct Generator: RandomNumberGenerator {
+        private let sodium = Sodium()
+
+        public init() {}
+
+        public mutating func next() -> UInt64 {
+            guard let bytes = self.sodium.randomBytes.buf(length: MemoryLayout<UInt64>.size) else {
+                fatalError("Sodium Random Number Generator is broken")
+            }
+
+            return bytes.withUnsafeBytes { pointer in
+                return pointer.load(as: UInt64.self)
+            }
+        }
+    }
+}
diff --git a/Tests/SodiumTests/ReadmeTests.swift b/Tests/SodiumTests/ReadmeTests.swift
@@ -155,6 +155,17 @@ class ReadmeTests : XCTestCase {
         let randomData = sodium.randomBytes.buf(length: 1000)
 
         XCTAssertNotNil(randomData)
+
+        var rng = RandomBytes.Generator()
+        let randomUInt32 = UInt32.random(in: 0...10, using: &rng)
+        let randomUInt64 = UInt64.random(in: 0...10, using: &rng)
+        let randomInt = Int.random(in: 0...10, using: &rng)
+        let randomDouble = Double.random(in: 0...1, using: &rng)
+
+        XCTAssert(randomUInt32 >= 0 && randomUInt32 <= 10)
+        XCTAssert(randomUInt64 >= 0 && randomUInt64 <= 10)
+        XCTAssert(randomInt >= 0 && randomInt <= 10)
+        XCTAssert(randomDouble >= 0 && randomDouble <= 1)
     }
 
     func testPasswordHashing() {

diff --git a/Tests/SodiumTests/SodiumTests.swift b/Tests/SodiumTests/SodiumTests.swift
@@ -182,6 +182,16 @@ class SodiumTests: XCTestCase {
         let seed = sodium.utils.hex2bin("00 11 22 33 44 55 66 77 88 99 aa bb cc dd ee ff 00 11 22 33 44 55 66 77 88 99 aa bb cc dd ee ff", ignore: " ")!
         let randomd = sodium.utils.bin2hex(sodium.randomBytes.deterministic(length: 10, seed: seed)!)!
         XCTAssertEqual(randomd, "444dc0602207c270b93f")
+
+        var c3 = 0
+        var rng = RandomBytes.Generator()
+        let ref3 = UInt32.random(in: 0...UInt32.max, using: &rng)
+        for _ in (0..<100) {
+            if UInt32.random(in: 0...UInt32.max, using: &rng) == ref3 {
+                c3 += 1
+            }
+        }
+        XCTAssert(c3 < 10)
     }
 
     func testShortHash() {