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Date:   Sat, 15 Jan 2022 23:26:16 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     keyrings@vger.kernel.org, David Howells <dhowells@redhat.com>,
        linux-crypto@vger.kernel.org,
        Marcel Holtmann <marcel@holtmann.org>,
        Denis Kenzior <denkenz@gmail.com>, stable@vger.kernel.org
Subject: Re: [PATCH] KEYS: fix length validation in keyctl_pkey_params_get_2()
Message-ID: <YeM7+Nyi2p7Yv7+Q@iki.fi>
References: <20220113200454.72609-1-ebiggers@kernel.org>
 <YeMWLyceg4xcwShF@iki.fi>
 <YeMmPs+gf+q7XUv4@sol.localdomain>
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On Sat, Jan 15, 2022 at 11:53:34AM -0800, Eric Biggers wrote:
> On Sat, Jan 15, 2022 at 08:45:03PM +0200, Jarkko Sakkinen wrote:
> > On Thu, Jan 13, 2022 at 12:04:54PM -0800, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > > 
> > > In many cases, keyctl_pkey_params_get_2() is validating the user buffer
> > > lengths against the wrong algorithm properties.  Fix it to check against
> > > the correct properties.
> > > 
> > > Probably this wasn't noticed before because for all asymmetric keys of
> > > the "public_key" subtype, max_data_size == max_sig_size == max_enc_size
> > > == max_dec_size.  However, this isn't necessarily true for the
> > > "asym_tpm" subtype (it should be, but it's not strictly validated).  Of
> > > course, future key types could have different values as well.
> > 
> > With a quick look, asym_tpm is TPM 1.x only, which only has 2048-bit RSA
> > keys.
> 
> The code allows other lengths, as well as the case where the "RSA key size"
> doesn't match the "public key size".  Probably both are bugs and they should
> both be 256 bytes (2048 bits) only.  Anyway, that would be a separate fix.
> 
> - Eric

I'm fine with the current commit message. E.g. I have no idea at this
point whether there should be in future separate asym_tpm2 or all bundled
to asym_tpm.

Acked-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko