simplify this down

README.md

@@ -23,7 +23,7 @@ I couldn't think of a better one and I wanted something notably distinct from st
 * To keep code light (and thus easier to debug, audit, etc.)
 * Because otherwise the module name is inaccurate
 * Because OpenSSH has their own specific variant
-    * Which means we can handle SSH-specific functionality if needed
+  * Which means we can handle SSH-specific functionality if needed
 * Because Golang/x/crypto has made it painfully clear that if you want something that deviates from what they think is "best practice", you need to do it yourself
 
 

consts.go

@@ -1,8 +1,30 @@
 package cc20p1305ssh
 
 const (
-	// KeySize is 32, but OpenSSH generates two separate keys.
+	/*
-	KeySize int = 32
+		FullKeySize is 64, but OpenSSH only uses the first half for the (true) KeySize.
+		(Normally in ChaCha20Poly1305, the second half is used for "additional data".
+		OpenSSH keys do not have "additional data".)
+	*/
+	FullKeySize int = 64 // Generated by Poly1305...
+	KeySize     int = 32 // The first 32 of which are used by ChaCha20.
+	// And for clarity, aliases for the above.
+	Poly1305KeySize int = FullKeySize
+	ChaCha20KeySize int = KeySize
+	// IvSize is 0 because OpenSSH uses a fixed internal constant (see IV).
+	IvSize int = 0
 	// NonceSize is literally the only reason I need to do this. The only reason.
 	NonceSize int = 16
+	// TagLen is the length of the Poly1305 tag.
+	TagLen int = 16
+)
+
+var (
+	// iv is the constant fixed IV.
+	iv []byte = []byte{
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+	}
 )

go.mod

@@ -1,3 +1,9 @@
 module r00t2.io/cc20p1305ssh
 
 go 1.18
+
+require (
+	github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a
+	golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a
+)

go.sum

@@ -0,0 +1,6 @@
+github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a h1:saTgr5tMLFnmy/yg3qDTft4rE5DY2uJ/cCxCe3q0XTU=
+github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a/go.mod h1:Bw9BbhOJVNR+t0jCqx2GC6zv0TGBsShs56Y3gfSCvl0=
+golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e h1:T8NU3HyQ8ClP4SEE+KbFlg6n0NhuTsN4MyznaarGsZM=
+golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a h1:dGzPydgVsqGcTRVwiLJ1jVbufYwmzD3LfVPLKsKg+0k=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

notes

@@ -0,0 +1,3 @@
+= KEY SIZES =
+In ChaCha20Poly1305, a key size of 32 bytes is needed.
+In OpenSSH, the KDF is used to generate a 64 byte key, and the first half is used.

testbin/main.go

@@ -0,0 +1,127 @@
+package main
+
+import (
+	`bytes`
+	`crypto/cipher`
+	`fmt`
+	`log`
+
+	`github.com/dchest/bcrypt_pbkdf`
+	`golang.org/x/crypto/chacha20poly1305`
+)
+
+var (
+	EncryptedBlob []byte = []byte{
+		0x21, 0xca, 0x93, 0x7d, 0x6b, 0x81, 0x5c, 0x67,
+		0x66, 0xc3, 0xd6, 0xa, 0xcc, 0x3a, 0xc7, 0x2d,
+		0x7f, 0xf7, 0xae, 0x6a, 0x41, 0x85, 0x18, 0xad,
+		0x37, 0x65, 0xfa, 0x8e, 0xb, 0x3b, 0x61, 0x72,
+		0x70, 0xaa, 0xc5, 0x0, 0xf4, 0x43, 0xb8, 0x21,
+		0xe6, 0x14, 0xe5, 0x7e, 0x81, 0x1f, 0x81, 0xe9,
+		0x66, 0xa1, 0xd0, 0x44, 0x72, 0xca, 0xaf, 0xe7,
+		0xbf, 0x6e, 0x95, 0x6f, 0xb3, 0x28, 0x3f, 0x92,
+		0x8f, 0xc, 0x61, 0xc9, 0x39, 0x69, 0x1, 0xd5,
+		0xe1, 0x43, 0x9b, 0xfe, 0x37, 0x7b, 0x4f, 0x9d,
+		0xe0, 0x73, 0x33, 0x5c, 0xc9, 0x24, 0x7, 0x9c,
+		0x5a, 0x96, 0x72, 0xb0, 0xe7, 0x36, 0x98, 0xc6,
+		0xa, 0x63, 0x9b, 0xda, 0xf0, 0x4f, 0xa, 0x74,
+		0xda, 0x77, 0xec, 0x8f, 0xc7, 0xdc, 0xe8, 0xa2,
+		0x62, 0x5c, 0x19, 0x6b, 0x83, 0x41, 0xa4, 0x71,
+		0x9f, 0x46, 0x78, 0x92, 0x64, 0x14, 0xc6, 0x63,
+		0x41, 0x91, 0x4c, 0xe9, 0xc0, 0x9f, 0x4d, 0x33,
+		0xb, 0x63, 0x1d, 0x96, 0x52, 0xa4, 0x68, 0x4a,
+		0x4e, 0x13, 0xbd, 0xff, 0x64, 0x8a, 0xa7, 0xb6,
+	}
+	UnknownData []byte = []byte{
+		0x9a, 0xa8, 0xaa, 0xa3,
+		0x73, 0x64, 0xb3, 0xaa,
+		0x78, 0x25, 0x23, 0x48,
+		0x7e, 0x79, 0x57, 0xab,
+	}
+	CombinedEncrypted = append(EncryptedBlob, UnknownData...)
+
+	// PLAIN
+	PrivKey []byte = []byte{
+		0xb9, 0x9a, 0xf2, 0xcb, 0x1e, 0xb3, 0x8c, 0xff,
+		0xdf, 0x76, 0x31, 0x22, 0x72, 0x56, 0xda, 0xf,
+		0xe3, 0xd1, 0xdb, 0x5a, 0xff, 0xea, 0x2e, 0x44,
+		0xc8, 0x5, 0x8d, 0xcc, 0xe0, 0x21, 0xae, 0x7e,
+	}
+	PubKey []byte = []byte{
+		0x9c, 0xf1, 0x14, 0x2f, 0xbb, 0x71, 0xac, 0xeb,
+		0xf3, 0xae, 0xa8, 0xd8, 0x9c, 0x51, 0x8c, 0x3,
+		0xa6, 0xd3, 0x66, 0x59, 0x4c, 0xee, 0xc5, 0x77,
+		0x4c, 0x4f, 0xf4, 0x7d, 0x57, 0xba, 0x26, 0x75,
+	}
+	EdKey []byte = append(PrivKey, PubKey...)
+)
+
+func main() {
+
+	var err error
+	var c cipher.AEAD
+	var kdfSalt []byte = []byte{
+		0xfa, 0x99, 0x09, 0xfd,
+		0xa2, 0xf5, 0xad, 0x42,
+		0xd2, 0x8e, 0x21, 0xe3,
+		0xb1, 0xcc, 0x6c, 0x94,
+	}
+	// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.chacha20poly1305
+	// https://rus-cert.github.io/ssh-chacha20-poly1305-drafts/ssh-chacha20-poly1305@openssh.html
+	// https://datatracker.ietf.org/doc/html/draft-josefsson-ssh-chacha20-poly1305-openssh-00
+	// https://pkg.go.dev/golang.org/x/crypto/chacha20poly1305
+	// var kdfKeyLen int = 512 / 8 // uses fixed 256 bits for chacha key, but it generates two keys...?
+	// var kdfKeyLen int = 256 // uses fixed 256 bits for chacha key
+	// var kdfKeyLen int = 32 // per golang pkg docs, 32 bytes (128 bits)...
+	var kdfKeyLen int = 64 // but per OpenSSH, 64
+	// var ivLen int = 0      // ??? per golang pkg docs, 12 bytes. per ssh package, though, 8(? or 0? seems to actually be 0). but needs 16 from...somewhere.
+	var ivLen int = 16
+	var kdfKey []byte
+	var subkey1, subkey2 []byte
+	var key []byte
+	var iv []byte
+	var nonce []byte
+	var plain []byte
+
+	if kdfKey, err = bcrypt_pbkdf.Key([]byte("testpassword"), kdfSalt, 16, kdfKeyLen+ivLen); err != nil {
+		log.Panicln(err)
+	}
+	key = kdfKey[0:kdfKeyLen]
+	iv = kdfKey[kdfKeyLen:(kdfKeyLen + ivLen)]
+	subkey1 = kdfKey[0:32]
+	subkey2 = kdfKey[32:]
+	// iv = subkey2[0:12]
+	nonce = []byte{
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+		0x0, 0x0, 0x0, 0x0,
+	}
+
+	fmt.Printf("kdf key (%d bytes): %#v\n", len(key), key)
+	fmt.Printf("kdf iv (%d bytes): %#v\n\n", len(iv), iv)
+
+	// if c, err = chacha20poly1305.New(key); err != nil {
+	if c, err = chacha20poly1305.New(subkey1); err != nil {
+		// if c, err = chacha20poly1305.New(subkey2); err != nil {
+		log.Panicln(err)
+	}
+	fmt.Printf("nonce size: %d\n", c.NonceSize())
+
+	plain = make([]byte, len(EncryptedBlob))
+	// if plain, err = c.Open(plain, iv, EncryptedBlob, UnknownData); err != nil {
+	// if plain, err = c.Open(plain, iv, CombinedEncrypted, nil); err != nil {
+	if plain, err = c.Open(plain, nonce, EncryptedBlob, nil); err != nil {
+		log.Panicln(err)
+	}
+
+	// fmt.Printf("%#v\n", c)
+
+	fmt.Printf("Decrypted:\n%#v\n", plain)
+	if bytes.Compare(plain, EdKey) != 0 {
+		fmt.Printf("\nOriginal:\n%#v\n", EdKey)
+	}
+
+	_ = subkey1
+	_ = subkey2
+}