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    SubjectRe: [PATCH] keys, trusted: select TPM2 hash algorithm
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    On Tue, 2015-10-27 at 12:42 +0200, Jarkko Sakkinen wrote:
    > n Mon, Oct 26, 2015 at 07:44:39AM +0200, Jarkko Sakkinen wrote:
    > > On Sun, Oct 25, 2015 at 03:21:31PM -0400, Mimi Zohar wrote:
    > > > On Sat, 2015-10-24 at 15:42 +0300, Jarkko Sakkinen wrote:
    > > > > Added 'hashalg=' option for selecting the hash algorithm.
    > > > >
    > > > > Currently available options are:
    > > > >
    > > > > * sha1
    > > > > * sha256
    > > > > * sha384
    > > > > * sha512
    > > > > * sm3_256
    > > >
    > > > Please consider using crypto/hash_info.c: hash_algo_name[], which
    > > > already define the algorithm string names. Use
    > > > include/crypto/hash_info.c to include a reference to this array.
    > >
    > > It wold work for me. I did ad-hoc because first example that I looked
    > > at was EcryptFS.

    After EVM, EcryptFS was the first subsystem to use trusted keys.
    Support for larger digests was later added to IMA.

    > > I need to add sm3_256 to that array.

    Unless there is kernel crypto support for this algorithm, I would
    conditionally include the algorithm, probably based on a Kconfig option.

    > > I've found three different ways to write it:
    > >
    > > * sm3256 (various google hits)
    > > * sm3-256 (various google hits)
    > > * sm3_256 (TPM 2.0 Structures specification)
    > >
    > > Maybe the second option would be the most appropriate?

    Right, If there aren't any standards, use the second option for the
    string and an underscore for the variable name.

    > > > Boot command line options should be prefixed with the subsystem name.
    > > > So instead of hashalg, please use tpm_hashalg. The boot command line
    > > > option needs to be documented in Documentation/kernel-parameters.txt.
    > >
    > > I see. My commit message is clearly inadequate. It's an option for the
    > > keyring syscalls.

    Sorry for the misunderstanding.

    > BTW, in IMA I see you have the hash algorithm as a boot parameter. I
    > guess it makes sense there because it works implicitly in the
    > background?

    The default hash algorithm is defined using the Kconfig IMA_DEFAULT_HASH
    option, but can be specified on the boot command line using "ima_hash=".

    > Sealing a trusted key is an explicit operation. That's why I thought
    > it'd be better to have it as an option for the syscall. Does this logic
    > make sense to your or not?

    It does.

    >
    > PS. Hey one more thing: this was supposed to be RFC, forgot to add
    > --subject-prefix="PATCH RFC". Sorry about that.

    :)

    Mimi



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