Re: [Qemu-devel] [PATCH for-2.9 1/2] crypto: add 3des-ede support when using libgcrypt/nettle

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Dec 07, 2016 at 05:19:38PM +0800, Longpeng (Mike) wrote:
> 
> 
> On 2016/12/7 16:52, Gonglei (Arei) wrote:
> 
> >> -----Original Message-----
> >> From: longpeng
> >> Sent: Wednesday, December 07, 2016 4:34 PM
> >> To: berrange@redhat.com; eblake@redhat.com; armbru@redhat.com;
> >> Gonglei (Arei)
> >> Cc: qemu-devel@nongnu.org; Wubin (H); Zhoujian (jay, Euler); longpeng
> >> Subject: [PATCH for-2.9 1/2] crypto: add 3des-ede support when using
> >> libgcrypt/nettle
> >>
> >> Libgcrypt and nettle support 3des-ede, so this patch add 3des-ede
> >> support when using libgcrypt or nettle.
> >>
> >> Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
> >> ---
> ......
> >> --- a/qapi/crypto.json
> >> +++ b/qapi/crypto.json
> >> @@ -63,6 +63,7 @@
> >>  # @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.
> >> +# @3des-ede: 3DES-EDE with 192 bit / 24 byte keys
> > 
> > Missing since 2.9 here.
> > 
> 
> Okay, I will add it in V2.
> 
> >>  # @cast5-128: Cast5 with 128 bit / 16 byte keys
> >>  # @serpent-128: Serpent with 128 bit / 16 byte keys
> >>  # @serpent-192: Serpent with 192 bit / 24 byte keys
> ......
> >> +    {
> >> +        /* Borrowed from linux-kernel crypto/testmgr.h */
> >> +        .path = "/crypto/cipher/3des-ede-ecb",
> >> +        .alg = QCRYPTO_CIPHER_ALG_3DES_EDE,
> >> +        .mode = QCRYPTO_CIPHER_MODE_ECB,
> >> +        .key =
> >> +            "0123456789abcdef5555555555555555"
> >> +            "fedcba9876543210",
> >> +        .plaintext =
> >> +            "736f6d6564617461",
> >> +        .ciphertext =
> >> +            "18d748e563620572",
> >> +    },
> >> +#endif
> > 
> > Pls adds the CTR mode test case as well.
> > 
> 
> Okay!
> 
> But I confuse with the 3DES's iv length now. I saw that cbc(3des-ede)'s iv-len
> can be 8 or 16 bytes, and ctr(3des-ede)'s iv-len is 24 bytes(according to
> linux-kernel crypto/testmgr.h).
> 
> However, I think qcrypto_cipher_get_iv_len() cannot distinguish a cipher alg
> with more than one iv-len.
> 
> Daniel, do you have any idea ?

Both nettle and libgcrypt require that the iv len match the block size of
the cipher, so iv-len for 3des must always be 24


Regards,
Daniel
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