Add a KDBX 4 codec: read, write, create
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.
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package kdbx
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import "encoding/binary"
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// BLAKE2b (RFC 7693). Argon2 is defined on top of it and the Go standard
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// library does not expose it, so it lives here with the RFC's test vectors.
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var blake2bIV = [8]uint64{
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0x6a09e667f3bcc908, 0xbb67ae8584caa73b, 0x3c6ef372fe94f82b, 0xa54ff53a5f1d36f1,
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0x510e527fade682d1, 0x9b05688c2b3e6c1f, 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179,
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}
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var blake2bSigma = [10][16]byte{
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15},
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{14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3},
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{11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4},
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{7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8},
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{9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13},
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{2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9},
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{12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11},
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{13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10},
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{6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5},
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{10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0},
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}
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type blake2b struct {
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h [8]uint64
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buf [128]byte
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n int // bytes buffered
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t uint64 // bytes compressed so far
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outLen int
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}
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// newBlake2b starts a hash producing outLen bytes, optionally keyed.
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func newBlake2b(outLen int, key []byte) *blake2b {
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b := &blake2b{outLen: outLen}
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b.h = blake2bIV
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b.h[0] ^= 0x01010000 ^ uint64(len(key))<<8 ^ uint64(outLen)
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if len(key) > 0 {
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var block [128]byte
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copy(block[:], key)
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b.Write(block[:])
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}
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return b
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}
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func (b *blake2b) Write(p []byte) {
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for len(p) > 0 {
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if b.n == 128 {
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b.t += 128
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b.compress(b.buf[:], false)
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b.n = 0
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}
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n := copy(b.buf[b.n:], p)
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b.n += n
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p = p[n:]
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}
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}
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func (b *blake2b) Sum() []byte {
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for i := b.n; i < 128; i++ {
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b.buf[i] = 0
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}
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b.t += uint64(b.n)
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b.compress(b.buf[:], true)
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out := make([]byte, 0, 64)
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for _, v := range b.h {
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out = binary.LittleEndian.AppendUint64(out, v)
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}
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return out[:b.outLen]
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}
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func (b *blake2b) compress(block []byte, last bool) {
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var m [16]uint64
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for i := range m {
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m[i] = binary.LittleEndian.Uint64(block[i*8:])
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}
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var v [16]uint64
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copy(v[:8], b.h[:])
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copy(v[8:], blake2bIV[:])
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v[12] ^= b.t
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// v[13] ^= high 64 bits of the counter, always zero for our inputs.
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if last {
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v[14] = ^v[14]
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}
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for r := 0; r < 12; r++ {
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s := blake2bSigma[r%10]
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gb2(&v, 0, 4, 8, 12, m[s[0]], m[s[1]])
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gb2(&v, 1, 5, 9, 13, m[s[2]], m[s[3]])
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gb2(&v, 2, 6, 10, 14, m[s[4]], m[s[5]])
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gb2(&v, 3, 7, 11, 15, m[s[6]], m[s[7]])
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gb2(&v, 0, 5, 10, 15, m[s[8]], m[s[9]])
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gb2(&v, 1, 6, 11, 12, m[s[10]], m[s[11]])
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gb2(&v, 2, 7, 8, 13, m[s[12]], m[s[13]])
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gb2(&v, 3, 4, 9, 14, m[s[14]], m[s[15]])
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}
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for i := range b.h {
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b.h[i] ^= v[i] ^ v[i+8]
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}
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}
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func gb2(v *[16]uint64, a, b, c, d int, x, y uint64) {
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v[a] = v[a] + v[b] + x
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v[d] = rotr64(v[d]^v[a], 32)
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v[c] = v[c] + v[d]
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v[b] = rotr64(v[b]^v[c], 24)
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v[a] = v[a] + v[b] + y
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v[d] = rotr64(v[d]^v[a], 16)
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v[c] = v[c] + v[d]
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v[b] = rotr64(v[b]^v[c], 63)
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}
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func rotr64(v uint64, n uint) uint64 { return v>>n | v<<(64-n) }
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// blake2bSum hashes the concatenation of parts into outLen bytes.
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func blake2bSum(outLen int, parts ...[]byte) []byte {
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h := newBlake2b(outLen, nil)
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for _, p := range parts {
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h.Write(p)
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}
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return h.Sum()
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}
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