root
5d66871527
Why: merging two edits of a vault means decrypting it, so the server needs a real KeePass implementation. Nothing else in this repository can be built on guesswork about the format. What: internal/kdbx reads and writes KDBX 4.0/4.1 with AES-256-CBC or ChaCha20 payloads, AES-KDF or Argon2d/Argon2id derivation, and the ChaCha20 inner stream for protected values. ChaCha20, BLAKE2b and Argon2 are implemented here, since the standard library has none of them and this repository carries no third-party dependencies. The XML payload is kept as a generic node tree rather than Go structs on purpose: a merge server that dropped elements it did not model would silently destroy data written by a newer KeePass. Anything unrecognised round-trips untouched. Unsupported ciphers, KDFs and KDBX 3 files are reported as such rather than guessed at, so a caller can fall back instead of losing data. Proved: ChaCha20 against RFC 8439, BLAKE2b against RFC 7693, all three Argon2 variants against RFC 9106. Round trips preserve unknown elements and multi-line values; a wrong password, a flipped payload byte and a flipped header byte are each rejected. Entry passwords appear nowhere in the file, encrypted or merely compressed. And the part that actually matters: keepassxc-cli 2.7.10 lists, reads and decrypts the protected values of a vault this code wrote, including at the production Argon2d cost, and this code reads back the file KeePassXC saves after editing it.
75 lines
2.0 KiB
Go
75 lines
2.0 KiB
Go
package kdbx
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import "encoding/binary"
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// ChaCha20 (RFC 8439) is the inner stream cipher KDBX 4 uses to protect
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// individual values inside the XML, and an optional outer cipher. The Go
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// standard library does not export it, so it is implemented here: the
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// algorithm is 60 lines and comes with published test vectors.
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type chacha20 struct {
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state [16]uint32
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block [64]byte
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used int // bytes of block already consumed
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}
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// newChaCha20 starts a keystream for a 32-byte key and 12-byte nonce.
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func newChaCha20(key, nonce []byte, counter uint32) *chacha20 {
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c := &chacha20{used: 64}
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c.state[0], c.state[1], c.state[2], c.state[3] =
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0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 // "expand 32-byte k"
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for i := 0; i < 8; i++ {
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c.state[4+i] = binary.LittleEndian.Uint32(key[i*4:])
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}
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c.state[12] = counter
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for i := 0; i < 3; i++ {
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c.state[13+i] = binary.LittleEndian.Uint32(nonce[i*4:])
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}
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return c
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}
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// XORKeyStream applies the keystream to src, continuing where the previous
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// call stopped. KDBX protects its values as one continuous stream, so this
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// must survive being called once per value.
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func (c *chacha20) XORKeyStream(dst, src []byte) {
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for i := range src {
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if c.used == 64 {
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c.nextBlock()
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}
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dst[i] = src[i] ^ c.block[c.used]
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c.used++
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}
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}
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func (c *chacha20) nextBlock() {
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var x [16]uint32
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copy(x[:], c.state[:])
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for i := 0; i < 10; i++ { // 20 rounds, two per iteration
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quarter(&x, 0, 4, 8, 12)
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quarter(&x, 1, 5, 9, 13)
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quarter(&x, 2, 6, 10, 14)
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quarter(&x, 3, 7, 11, 15)
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quarter(&x, 0, 5, 10, 15)
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quarter(&x, 1, 6, 11, 12)
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quarter(&x, 2, 7, 8, 13)
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quarter(&x, 3, 4, 9, 14)
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}
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for i := range x {
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binary.LittleEndian.PutUint32(c.block[i*4:], x[i]+c.state[i])
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}
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c.state[12]++
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c.used = 0
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}
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func quarter(x *[16]uint32, a, b, cc, d int) {
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x[a] += x[b]
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x[d] = rotl(x[d]^x[a], 16)
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x[cc] += x[d]
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x[b] = rotl(x[b]^x[cc], 12)
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x[a] += x[b]
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x[d] = rotl(x[d]^x[a], 8)
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x[cc] += x[d]
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x[b] = rotl(x[b]^x[cc], 7)
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}
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func rotl(v uint32, n uint) uint32 { return v<<n | v>>(32-n) }
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