Re: [PATCH v2 1/7] crypto: arc4 - refactor arc4 core code into separate library

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Jun 10, 2019 at 06:10:41PM +0200, Ard Biesheuvel wrote:
> On Mon, 10 Jun 2019 at 18:06, Eric Biggers <ebiggers@kernel.org> wrote:
> >
> > Just some bike shedding:
> >
> > On Sun, Jun 09, 2019 at 01:55:03PM +0200, Ard Biesheuvel wrote:
> > > diff --git a/include/crypto/arc4.h b/include/crypto/arc4.h
> > > index 5b2c24ab0139..62ac95ec6860 100644
> > > --- a/include/crypto/arc4.h
> > > +++ b/include/crypto/arc4.h
> > > @@ -6,8 +6,21 @@
> > >  #ifndef _CRYPTO_ARC4_H
> > >  #define _CRYPTO_ARC4_H
> > >
> > > +#include <linux/types.h>
> > > +
> > >  #define ARC4_MIN_KEY_SIZE    1
> > >  #define ARC4_MAX_KEY_SIZE    256
> > >  #define ARC4_BLOCK_SIZE              1
> > >
> > > +struct crypto_arc4_ctx {
> > > +     u32 S[256];
> > > +     u32 x, y;
> > > +};
> > > +
> > > +int crypto_arc4_set_key(struct crypto_arc4_ctx *ctx, const u8 *in_key,
> > > +                     unsigned int key_len);
> > > +
> > > +void crypto_arc4_crypt(struct crypto_arc4_ctx *ctx, u8 *out, const u8 *in,
> > > +                    unsigned int len);
> >
> > How about naming these just arc4_* instead of crypto_arc4_*?  The crypto_*
> > prefix is already used mostly for crypto API helper functions, i.e. functions
> > that take take one of the abstract crypto API types like crypto_skcipher,
> > shash_desc, etc.  For lib functions, the bare name seems more appropriate.  See
> > e.g. sha256_update() vs. crypto_sha256_update().
> >
> 
> That is also fine, although I am slightly concerned that we may run
> into trouble with other algorithms in the future. But I do agree it
> makes sense to make a clear distinction with the full blown API.
> 
> > > +++ b/lib/crypto/Makefile
> > > @@ -0,0 +1,3 @@
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +
> > > +obj-$(CONFIG_CRYPTO_LIB_ARC4) += libarc4.o
> > > diff --git a/lib/crypto/libarc4.c b/lib/crypto/libarc4.c
> > > new file mode 100644
> > > index 000000000000..b828af2cc03b
> > > --- /dev/null
> > > +++ b/lib/crypto/libarc4.c
> > > @@ -0,0 +1,74 @@
> >
> > How about arc4.c instead of libarc4.c?  The second "lib" is redundant, given
> > that the file is already in the lib/ directory.
> >
> 
> The problem here is that we'll end up with two modules named arc4.ko,
> one in crypto/ and one in lib/crypto/. Perhaps we should rename the
> other one? (especially once it implements ecb(arc4) only.)

Another option is to do:

obj-$(CONFIG_CRYPTO_LIB_ARC4) += libarc4.o
libarc4-y := arc4.o

Also, CONFIG_CRYPTO_LIB_ARC4 needs to actually be a tristate.
It seems you accidentally made it a bool:

> +config CRYPTO_LIB_ARC4
> +	bool
> +

- Eric