[PATCH 07/10] password: add pbkdf2 support

[Jean-Christophe PLAGNIOL-VILLARD]

On 12:58 Mon 16 Mar     , Jan Lübbe wrote:
> On Mo, 2015-03-16 at 12:52 +0100, Jean-Christophe PLAGNIOL-VILLARD
> wrote:
> > On 12:41 Mon 16 Mar     , Jan Lübbe wrote:
> > > On Mo, 2015-03-16 at 12:25 +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > > > > Yes, definitely. We must use the algorithms as they are intended to be
> > > > > used.
> > > > > 
> > > > > If we try to move users away from RSA2048 because it will be vulnerable
> > > > > in the future, we should not go against established practice for
> > > > > password salts by hard-coding it. 
> > > > I'm not against it but with the barebox entropy did not see the point to use
> > > > it.
> > > > 
> > > > so how do we generate the salt? what length
> > > > 
> > > > Personnaly I'll prefer
> > > > 
> > > > a random 64 bytes | sha256 | take first 32bytes. | pbkdf2 10000 round
> > > 
> > > Running SHA-256 on random data is useless for security.
> > SHA256 is to improve the entrpopy not security
> 
> Running a deterministic algorithm cannot increase entropy (only reduce
> it).

check the kennel algo for PRGN

and youp will see why I want to use a sha

> 
> > > Just get
> > > <hash-size> bytes from /dev/urandom on the host. We could generate a
> > > file with the compile-time SALT which is then included.
> > > 
> > > On the running barebox, we could use SHA to hash the old password file
> > > together with the current timer value. At least until we have something
> > > better.
> > > 
> > > > result a 64 bytes password file <salt 32 byes><key 32 bytes>
> > > 
> > > Yes. As we select the algorithm at compile time, we don't the to save it
> > > in the file.
> > 
> > this is for barebox as we may not have any passwd file
> 
> The same applies also to the default_passwd compiled in variable.
> 
> Currently we have:
> PASSWD_FILE := $(shell cd $(srctree); find $(CONFIG_PASSWORD_DEFAULT) -type f)
> cmd_pwd_h = echo -n "static const char default_passwd[] = \"" > $@; \
>         cat $< | tr -d '\n' >> $@; \
>         echo "\";" >> $@
> 
> include/generated/passwd.h: $(PASSWD_FILE)
>         $(call if_changed,pwd_h)
> 
> This would need to run the hash/pbkdf2 and store salt+key.

no as the current current code expect you to give the correct file format for
the currently use password

so today the output of openssl

but yes we may need to do more here

Best Regards,
J.