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Subject: Re: [PATCH 00/14] KEYS: Add support for PGP keys and signatures
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     James Bottomley <James.Bottomley@hansenpartnership.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Roberto Sassu <roberto.sassu@huawei.com>, dhowells@redhat.com,
        dwmw2@infradead.org, herbert@gondor.apana.org.au,
        davem@davemloft.net, keyrings@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-fscrypt@vger.kernel.org, linux-kernel@vger.kernel.org,
        zohar@linux.ibm.com
References: <20220111180318.591029-1-roberto.sassu@huawei.com>
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 <d92912bba61ee37e42d04b64073b9031604acc0f.camel@HansenPartnership.com>
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From:   Antony Vennard <antony@vennard.ch>
Message-ID: <24206663-b0ee-8c99-28c3-da4d433dee9d@vennard.ch>
Date:   Sun, 23 Jan 2022 22:00:18 +0100
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On 19/01/2022 00:03, Eric Biggers wrote:
> On Tue, Jan 18, 2022 at 09:50:21PM +0100, Antony Vennard wrote:
>>
>> Hi All,

> It's worth noting that if fs-verity built-in signatures are used, a trusted
> userspace program is still required to determine and enforce the policy of which
> files are required to be signed.  The kernel only handles the actual signature
> verification.  This was basically a proof-of-concept which reused the kernel's
> module signature verification code (which happens to use PKCS#7).
> 
> I'd encourage new users to either go all-in on a userspace solution, using a
> trusted userspace program to verify signatures of fs-verity file digests;
> *or* go all-in on an in-kernel solution, using the IMA support for fs-verity
> which Mimi Zohar is working on.  A userspace solution could use a simple
> signature format, using a modern algorithm such as Ed25519.  IMA uses a simple
> signature format too, though it uses a complex format (X.509) for public keys.

FWIW I checked some of the options for hardware key storage. Thales HSMs 
support Ed25519, at least according to their marketing materials. 
Similarly Javacard 3.1 supports (will support) X/Ed 25519/448, so when 
tokens supporting this emerge (if they haven't already) hardware support 
for modern algorithms should exist too.

I therefore agree. Use Ed25519.

Antony