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Use BlockCipher.blockSize as a result length in randomIV helper #893

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Use BlockCipher.blockSize as a result length in randomIV helper #893

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a220322
Use `BlockCipher.blockSize` as a result length in `randomIV` helper
evnik Oct 4, 2021
34f52c5
Example of `randomIV` usage is updated
evnik Oct 5, 2021
ec28c79
`randomIV(_ count: Int)` helper is returned and marked as deprecated
evnik Nov 24, 2021
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -389,7 +389,7 @@ let key = try PKCS5.PBKDF2(
).calculate()

/* Generate random IV value. IV is public value. Either need to generate, or get it from elsewhere */
let iv = AES.randomIV(AES.blockSize)
let iv = AES.randomIV()

/* AES cryptor instance */
let aes = try AES(key: key, blockMode: CBC(iv: iv), padding: .pkcs7)
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2 changes: 1 addition & 1 deletion Sources/CryptoSwift/BlockCipher.swift
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Expand Up @@ -13,6 +13,6 @@
// - This notice may not be removed or altered from any source or binary distribution.
//

protocol BlockCipher: Cipher {
public protocol BlockCipher: Cipher {
static var blockSize: Int { get }
}
16 changes: 6 additions & 10 deletions Sources/CryptoSwift/Cryptors.swift
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Expand Up @@ -29,16 +29,12 @@ public protocol Cryptors: AnyObject {

/// Cryptor suitable for decryption
func makeDecryptor() throws -> Cryptor & Updatable

/// Generate array of random bytes. Helper function.
static func randomIV(_ blockSize: Int) -> Array<UInt8>
}

extension Cryptors {
/// Generate array of random values.
/// Convenience helper that uses `Swift.RandomNumberGenerator`.
/// - Parameter count: Length of array
public static func randomIV(_ count: Int) -> Array<UInt8> {
(0..<count).map({ _ in UInt8.random(in: 0...UInt8.max) })
public extension Cryptors where Self: BlockCipher {
/// Generates array of random bytes. `blockSize` is used as length of the result array.
/// Convenience helper that uses `Swift.SystemRandomNumberGenerator`.
static func randomIV() -> [UInt8] {
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can it be randomIV(_ count: Int = Self.blockSize) ?

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It can, but then it defeats the purpose of these changes. I'd like to make this helper hard to use in a wrong way.

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It's not, really. It keep the backward compatibility, while use the blockSize default now

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Well, I've returned randomIV(_ count: Int) helper marking it as deprecated, so existing code won't be broken after upgrade to the new version

(0..<Self.blockSize).map({ _ in UInt8.random(in: 0...UInt8.max) })
}
}
}
6 changes: 6 additions & 0 deletions Tests/CryptoSwiftTests/AESTests.swift
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Expand Up @@ -345,6 +345,11 @@ final class AESTests: XCTestCase {
}
}

func testAESRandomIV() {
let iv = AES.randomIV()
XCTAssertEqual(iv.count, AES.blockSize)
}

func testAESWithWrongKey() {
let key: Array<UInt8> = [0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c]
let key2: Array<UInt8> = [0x22, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x33]
Expand Down Expand Up @@ -678,6 +683,7 @@ extension AESTests {
("testAESDecryptCTRSeek", testAESDecryptCTRSeek),
("testAESEncryptCTRIrregularLengthIncrementalUpdate", testAESEncryptCTRIrregularLengthIncrementalUpdate),
("testAESEncryptCTRStream", testAESEncryptCTRStream),
("testAESRandomIV", testAESRandomIV),
("testIssue298", testIssue298),
("testIssue394", testIssue394),
("testIssue411", testIssue411),
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4 changes: 2 additions & 2 deletions Tests/CryptoSwiftTests/Access.swift
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Expand Up @@ -29,8 +29,8 @@ class Access: XCTestCase {
}

func testRandomIV() {
_ = AES.randomIV(AES.blockSize)
_ = ChaCha20.randomIV(ChaCha20.blockSize)
_ = AES.randomIV()
_ = ChaCha20.randomIV()
}

func testDigest() {
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8 changes: 7 additions & 1 deletion Tests/CryptoSwiftTests/ChaCha20Tests.swift
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Expand Up @@ -106,6 +106,11 @@ final class ChaCha20Tests: XCTestCase {
XCTFail()
}
}

func testChaCha20RandomIV() {
let iv = ChaCha20.randomIV()
XCTAssertEqual(iv.count, ChaCha20.blockSize)
}
}

extension ChaCha20Tests {
Expand All @@ -114,7 +119,8 @@ extension ChaCha20Tests {
("testChaCha20", testChaCha20),
("testCore", testCore),
("testVector1Py", testVector1Py),
("testChaCha20EncryptPartial", testChaCha20EncryptPartial)
("testChaCha20EncryptPartial", testChaCha20EncryptPartial),
("testChaCha20RandomIV", testChaCha20RandomIV)
]

return tests
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