Re: [Phishing Risk] [External] Re: [PATCH 4/7] crypto: Add ECDSA key parser

[Philippe Mathieu-Daudé]

On 14/6/22 03:43, 何磊 wrote:
> Hi Philippe, lots of thanks for your review!
>
> > On Jun 13, 2022, at 10:19 PM, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> >
> > On 13/6/22 10:45, Lei He wrote:
> > > Add ECDSA key parser and ECDSA signautre parser.
> > > Signed-off-by: lei he <helei.sig11@bytedance.com>
> > > ---
> > >   crypto/ecdsakey-builtin.c.inc | 248 ++++++++++++++++++++++++++++++++++++++++++
> > >   crypto/ecdsakey.c             | 118 ++++++++++++++++++++
> > >   crypto/ecdsakey.h             |  66 +++++++++++
> > >   crypto/meson.build            |   1 +
> > >   4 files changed, 433 insertions(+)
> > >   create mode 100644 crypto/ecdsakey-builtin.c.inc
> > >   create mode 100644 crypto/ecdsakey.c
> > >   create mode 100644 crypto/ecdsakey.h
> > > diff --git a/crypto/ecdsakey-builtin.c.inc b/crypto/ecdsakey-builtin.c.inc
> > > new file mode 100644
> > > index 0000000000..5da317ec44
> > > --- /dev/null
> > > +++ b/crypto/ecdsakey-builtin.c.inc
> > > @@ -0,0 +1,248 @@
> > > +/*
> > > + * QEMU Crypto akcipher algorithms
> > > + *
> > > + * Copyright (c) 2022 Bytedance
> > > + * Author: lei he <helei.sig11@bytedance.com>
> > > + *
> > > + * This library is free software; you can redistribute it and/or
> > > + * modify it under the terms of the GNU Lesser General Public
> > > + * License as published by the Free Software Foundation; either
> > > + * version 2.1 of the License, or (at your option) any later version.
> > > + *
> > > + * This library is distributed in the hope that it will be useful,
> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > > + * Lesser General Public License for more details.
> > > + *
> > > + * You should have received a copy of the GNU Lesser General Public
> > > + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> > > + *
> > > + */
> > > +
> > > +#include "der.h"
> > > +#include "ecdsakey.h"
> > > +
> > > +#define QCRYPTO_ECDSA_PUBKEY_FMT_UNCOMPRESSED 0x04
> > > +
> > > +static int extract_mpi(void *ctx, const uint8_t *value,
> > > +                       size_t vlen, Error **errp)
> > > +{
> > > +    QCryptoAkCipherMPI *mpi = (QCryptoAkCipherMPI *)ctx;
> > > +    if (vlen == 0) {
> > > +        error_setg(errp, "Empty mpi field");
> > > +        return -1;
> >
> > Functions taking Error* param usually return a boolean.
>
> It's a good idea to make such functions that only return 0 or -1 return bool 
> directly, but this change
> will require modification of rsakey related code. If you strongly request it, I 
> will modify it in another patch.

QCryptoDERDecodeCb seems to only return a boolean, so should follow the
style recommended in 
https://gitlab.com/qemu-project/qemu/-/commit/e3fe3988d7. Can be done 
later as a follow-up cleanup of course.

> > > +    }
> > > +    mpi->data = g_memdup2(value, vlen);
> > > +    mpi->len = vlen;
> > > +    return 0;
> > > +}
> > > +
> > > +static int extract_version(void *ctx, const uint8_t *value,
> > > +                           size_t vlen, Error **errp)
> > > +{
> > > +    uint8_t *version = (uint8_t *)ctx;
> > > +    if (vlen != 1 || *value > 1) {
> > > +        error_setg(errp, "Invalid rsakey version");
> > > +        return -1;
> > > +    }
> > > +    *version = *value;
> > > +    return 0;
> > > +}
> > > +
> > > +static int extract_cons_content(void *ctx, const uint8_t *value,
> > > +                                size_t vlen, Error **errp)
> > > +{
> > > +    const uint8_t **content = (const uint8_t **)ctx;
> > > +    if (vlen == 0) {
> > > +        error_setg(errp, "Empty sequence");
> > > +        return -1;
> > > +    }
> > > +    *content = value;
> >
> > You need to check (vlen >= sizeof(uint8_t *)) to avoid overrun.
>
> The decoder will parse the meta data of ASN1 types and pass the real data part 
> to the callback function.
> The above statement only saves the starting address of the ‘data part' and does 
> not actually access the
> data, so there is no need to check the size of vlen.

Oops, indeed you are right :)

> > > +    return 0;
> > > +}
> > > +
> > > +static int __qcrypto_akcipher_builtin_ecdsa_pubkey_parse(
> > > +    QCryptoAkCipherECDSAKey *ecdsa,
> > > +    const uint8_t *key, size_t keylen, Error **errp);
> >
> > Why use the reserved __prefix?
>
> I will fix it later.