crypto: implement Output Feedback (OFB) Mode for AES and DES (#13583)

vlib/crypto/cipher/aes_ofb_test.v

@@ -0,0 +1,31 @@
+import crypto.aes
+import crypto.cipher
+
+fn test_aes_ofb() {
+	key := '6368616e676520746869732070617373'.bytes()
+	iv := '1234567890123456'.bytes()
+	str := '73c86d43a9d700a253a96c85b0f6b03ac9792e0e757f869cca306bd3cba1c62b'
+
+	mut src := str.bytes()
+
+	aes_ofb_en(mut src, key, iv)
+	assert src.hex() == '04380c1470ab2d8a0b3f9b4c1949b8aca120db226fa0a848236f9904f786dfc39bc433b5d3870d1cfdef36debdee5e6f39b0e8e9462b0151d61e822944181b51'
+	dump(src.hex())
+	mut plaintext := src.clone()
+	aes_ofb_de(mut plaintext, key, iv)
+	assert plaintext.bytestr() == str
+	dump(plaintext.bytestr())
+	println('test_aes_ofb ok')
+}
+
+fn aes_ofb_en(mut src []byte, key []byte, iv []byte) {
+	block := aes.new_cipher(key)
+	mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}
+
+fn aes_ofb_de(mut src []byte, key []byte, iv []byte) {
+	block := aes.new_cipher(key)
+	mut mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}

vlib/crypto/cipher/des_ofb_test.v

@@ -0,0 +1,54 @@
+import crypto.des
+import crypto.cipher
+
+const (
+	key = '123456789012345678901234'.bytes()
+	iv  = 'abcdegfh'.bytes()
+	str = '73c86d43a9d700a253a96c85b0f6b03ac9792e0e757f869cca306bd3cba1c62b'
+)
+
+fn test_triple_des_ofb() {
+	mut src := str.bytes()
+
+	triple_des_ofb_en(mut src, key, iv)
+	assert src.hex() == '00d963619a67c84e46741a47e972e407121885af78b8ef64a9b835366e5314b8031940a9c33a4c0e1ce3b417c9fd04c3f99f31821ebfc9f8cb9e80cc50cfd91e'
+
+	triple_des_ofb_de(mut src, key, iv)
+	assert src.bytestr() == str
+	println('test_triple_des_ofb ok')
+}
+
+fn test_des_ofb() {
+	mut src := str.bytes()
+
+	des_ofb_en(mut src, key[..8], iv)
+	assert src.hex() == '2743e2164b860456c1313fb9b1196a70bb217dfad57be81cb10f368dd1ee13b06bb776eb52e0b4f6b1af32f44b8f094cfd3c0892021a2aa93f6a9e2139ba26f3'
+
+	des_ofb_de(mut src, key[..8], iv)
+	assert src.bytestr() == str
+	println('test_des_ofb ok')
+}
+
+fn des_ofb_en(mut src []byte, key []byte, iv []byte) {
+	block := des.new_cipher(key)
+	mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}
+
+fn des_ofb_de(mut src []byte, key []byte, iv []byte) {
+	block := des.new_cipher(key)
+	mut mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}
+
+fn triple_des_ofb_en(mut src []byte, key []byte, iv []byte) {
+	block := des.new_triple_des_cipher(key)
+	mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}
+
+fn triple_des_ofb_de(mut src []byte, key []byte, iv []byte) {
+	block := des.new_triple_des_cipher(key)
+	mut mode := cipher.new_ofb(block, iv)
+	mode.xor_key_stream(mut src, src.clone())
+}

vlib/crypto/cipher/ofb.v

@@ -0,0 +1,66 @@
+// The source code refers to the go standard library, which will be combined with AES in the future.
+//
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+//
+// OFB (Output Feedback) Mode.
+// See NIST SP 800-38A, pp 13-15
+module cipher
+
+import crypto.internal.subtle
+
+struct Ofb {
+mut:
+	b        Block
+	next     []byte
+	out      []byte
+	out_used int
+}
+
+// new_ofb returns a Ofb that encrypts or decrypts using the block cipher b
+// in output feedback mode. The initialization vector iv's length must be equal
+// to b's block size.
+pub fn new_ofb(b Block, iv []byte) Ofb {
+	block_size := b.block_size
+	if iv.len != block_size {
+		panic('cipher.new_ofb: IV length must be equal block size')
+	}
+	x := Ofb{
+		b: b
+		out: []byte{len: b.block_size}
+		next: []byte{len: b.block_size}
+		out_used: block_size
+	}
+
+	copy(x.next, iv)
+
+	return x
+}
+
+pub fn (x &Ofb) xor_key_stream(mut dst_ []byte, src_ []byte) {
+	unsafe {
+		mut dst := *dst_
+		mut src := src_
+		if dst.len < src.len {
+			panic('crypto.cipher.xor_key_stream: output smaller than input')
+		}
+
+		if subtle.inexact_overlap(dst[..src.len], src) {
+			panic('crypto.cipher.xor_key_stream: invalid buffer overlap')
+		}
+
+		for src.len > 0 {
+			if x.out_used == x.out.len {
+				x.b.encrypt(mut x.out, x.next)
+				x.out_used = 0
+			}
+
+			copy(x.next, x.out)
+
+			n := xor_bytes(mut dst, src, x.out)
+			dst = dst[n..]
+			src = src[n..]
+			x.out_used += n
+		}
+	}
+}