Daniel P. Berrangé <berra...@redhat.com> writes: > On Wed, Jul 07, 2021 at 02:47:15PM +0200, Markus Armbruster wrote: >> Daniel P. Berrangé <berra...@redhat.com> writes: >> >> > Currently the crypto layer exposes support for a 'des-rfb' >> > algorithm which is just normal single-DES, with the bits >> > in each key byte reversed. This special key munging is >> > required by the RFB protocol password authentication >> > mechanism. >> > >> > Since the crypto layer is generic shared code, it makes >> > more sense to do the key byte munging in the VNC server >> > code, and expose normal single-DES support. >> > >> > Signed-off-by: Daniel P. Berrangé <berra...@redhat.com> >> > --- >> >> [...] >> >> > diff --git a/qapi/crypto.json b/qapi/crypto.json >> > index 7116ae9a46..6b3fadabac 100644 >> > --- a/qapi/crypto.json >> > +++ b/qapi/crypto.json >> > @@ -66,7 +66,7 @@ >> > # @aes-128: AES with 128 bit / 16 byte keys >> > # @aes-192: AES with 192 bit / 24 byte keys >> > # @aes-256: AES with 256 bit / 32 byte keys >> > -# @des-rfb: RFB specific variant of single DES. Do not use except in VNC. >> > +# @des: DES with 56 bit / 8 byte keys. Do not use except in VNC. >> > # @3des: 3DES(EDE) with 192 bit / 24 byte keys (since 2.9) >> > # @cast5-128: Cast5 with 128 bit / 16 byte keys >> > # @serpent-128: Serpent with 128 bit / 16 byte keys >> > @@ -80,7 +80,7 @@ >> > { 'enum': 'QCryptoCipherAlgorithm', >> > 'prefix': 'QCRYPTO_CIPHER_ALG', >> > 'data': ['aes-128', 'aes-192', 'aes-256', >> > - 'des-rfb', '3des', >> > + 'des', '3des', >> > 'cast5-128', >> > 'serpent-128', 'serpent-192', 'serpent-256', >> > 'twofish-128', 'twofish-192', 'twofish-256']} >> >> Is enum value "des-rfb" part of any external interface? > > Strictly speaking, yes, but in reality it doesn't matter. > > > The only place in QEMU that actually uses DES-RFB is the > VNC server code. That is an indirect usage when the user > sets the "password" option flag in QemuOpts. The fact that > it uses DES-RFB is an internal impl detail. > > The one place that does publically expose ability to set a > field using the QCryptoCipherAlgorithm enum type is the > LUKS support in the block layer: > > { 'struct': 'QCryptoBlockCreateOptionsLUKS', > 'base': 'QCryptoBlockOptionsLUKS', > 'data': { '*cipher-alg': 'QCryptoCipherAlgorithm', > '*cipher-mode': 'QCryptoCipherMode', > '*ivgen-alg': 'QCryptoIVGenAlgorithm', > '*ivgen-hash-alg': 'QCryptoHashAlgorithm', > '*hash-alg': 'QCryptoHashAlgorithm', > '*iter-time': 'int'}} > > eg exposed on CLI as: > > $ qemu-img create -f luks -o cipher-alg=NNN foo.luks 1G > > or equivalant with QMP blockdev-create > > While the QMP schema allows any valid QCryptoCipherAlgorithm > string to be set, the actual implementation does not. > > The crypto/block-luks.c code has a map between cipher algs > and LUKS format algoritm names: > > > static const QCryptoBlockLUKSCipherNameMap > qcrypto_block_luks_cipher_name_map[] = { > { "aes", qcrypto_block_luks_cipher_size_map_aes }, > { "cast5", qcrypto_block_luks_cipher_size_map_cast5 }, > { "serpent", qcrypto_block_luks_cipher_size_map_serpent }, > { "twofish", qcrypto_block_luks_cipher_size_map_twofish }, > }; > > If it isn't in that table, it can't be used. IOW, the only > scenario we're affecting in this rename is one which would > already result in an error condition > > Original behaviour: > > $ qemu-img create -f luks --object secret,id=sec0,data=123 -o > cipher-alg=des-rfb,key-secret=sec0 demo.luks 1G > Formatting 'demo.luks', fmt=luks size=1073741824 key-secret=sec0 > cipher-alg=des-rfb > qemu-img: demo.luks: Algorithm 'des-rfb' not supported > > New behaviour: > > $ qemu-img create -f luks --object secret,id=sec0,data=123 -o > cipher-alg=des-rfb,key-secret=sec0 demo.luks 1G > Formatting 'demo.luks', fmt=luks size=1073741824 key-secret=sec0 > cipher-alg=des-fish > qemu-img: demo.luks: Invalid parameter 'des-rfb' > > I considered this incompatibility to be acceptable, and thus > not worth going through a deprecation dance.
Thanks for the explanation. I agree the deprecation dance is not necessary here. Please consider explaining this in your commit message. Suggest to append a variation of the tail of your explanation: Replacing cipher 'des-rfb' by 'des' looks like an incompatible interface change, but it doesn't matter. While the QMP schema allows ... qemu-img: demo.luks: Invalid parameter 'des-rfb' Also consider tweaking the title to crypto: Replace 'des-rfb' cipher by 'des' because it's not actually just a rename. Reviewed-by: Markus Armbruster <arm...@redhat.com>