From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "James Bottomley" <James.Bottomley@HansenPartnership.com>,
"Herbert Xu" <herbert@gondor.apana.org.au>
Cc: <linux-integrity@vger.kernel.org>, <keyrings@vger.kernel.org>,
<Andreas.Fuchs@infineon.com>,
"James Prestwood" <prestwoj@gmail.com>,
"David Woodhouse" <dwmw2@infradead.org>,
"Eric Biggers" <ebiggers@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"open list:CRYPTO API" <linux-crypto@vger.kernel.org>,
"open list" <linux-kernel@vger.kernel.org>,
"Peter Huewe" <peterhuewe@gmx.de>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Mimi Zohar" <zohar@linux.ibm.com>,
"David Howells" <dhowells@redhat.com>,
"Paul Moore" <paul@paul-moore.com>,
"James Morris" <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
"open list:SECURITY SUBSYSTEM"
<linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v2 4/6] KEYS: trusted: Move tpm2_key_decode() to the TPM driver
Date: Wed, 22 May 2024 00:17:13 +0300 [thread overview]
Message-ID: <D1FMVEJWGLEW.14QGHPAYPHQG1@kernel.org> (raw)
In-Reply-To: <cc3d952f8295b52b052fbffe009b796ffb45707a.camel@HansenPartnership.com>
On Tue May 21, 2024 at 9:18 PM EEST, James Bottomley wrote:
> On Tue, 2024-05-21 at 06:16 +0300, Jarkko Sakkinen wrote:
> [...]
> > diff --git a/include/crypto/tpm2_key.h b/include/crypto/tpm2_key.h
> > new file mode 100644
> > index 000000000000..acf41b2e0c92
> > --- /dev/null
> > +++ b/include/crypto/tpm2_key.h
> > @@ -0,0 +1,33 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +#ifndef __LINUX_TPM2_KEY_H__
> > +#define __LINUX_TPM2_KEY_H__
> > +
> > +#include <linux/slab.h>
> > +
> > +/*
> > + * TPM2 ASN.1 key
> > + */
> > +struct tpm2_key {
> > + u32 parent;
> > + const u8 *blob;
> > + u32 blob_len;
> > + const u8 *pub;
> > + u32 pub_len;
> > + const u8 *priv;
> > + u32 priv_len;
> > +};
> > +
> > +int tpm2_key_decode(const u8 *src, u32 src_len, struct tpm2_key
> > *key,
> > + u32 max_key_len);
>
> I don't think this is a good idea. Trusted keys already have a pre-
> defined max payload size (MAX_BLOB_SIZE in include/keys/trusted-type.h)
> and I've already had to increase this several times because once you
> get policy attached to a key, it can get pretty big (over a page).
> Exactly the same thing will happen to asymmetric keys as well, so it
> does make sense that they share the same maximum (probably in a more
> generic header, though).
ECDSA and RSA have different space requirements. With that solution you
actually max out space requirements given same cap for everything.
Even tpm2_key_ecdsa should use a different value than tpm2_key_rsa to
save memory.
> Since the code already right sizes the allocation and all we check with
> this is whether it's over a pre-defined maximum, it's way easier if
> that maximum is defined in a header rather than passed in in several
> places making increasing the maximum really hard because you have to
> chase all the threading.
You don't save a single byte of memory with any constant that dictates
the size requirements for multiple modules in two disjoint subsystems.
You are maximizing the use of memory.
> James
BR, Jarkko
next prev parent reply other threads:[~2024-05-21 21:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-21 3:16 [PATCH v2 0/6] KEYS: asymmetric: tpm2_key_rsa Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 1/6] crypto: rsa-pkcs1pad: export rsa1_asn_lookup() Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 2/6] lib: Expand asn1_encode_integer() to variable size integers Jarkko Sakkinen
2024-05-21 5:36 ` [EXTERNAL] " Bharat Bhushan
[not found] ` < <SN7PR18MB5314CFBD18B011F292809EBFE3EA2@SN7PR18MB5314.namprd18.prod.outlook.com>
2024-05-21 6:21 ` Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 3/6] tpm: Export tpm2_load_context() Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 4/6] KEYS: trusted: Move tpm2_key_decode() to the TPM driver Jarkko Sakkinen
2024-05-21 18:18 ` James Bottomley
2024-05-21 21:17 ` Jarkko Sakkinen [this message]
2024-05-21 21:44 ` David Howells
2024-05-21 21:59 ` James Bottomley
2024-05-21 22:45 ` Jarkko Sakkinen
2024-05-21 22:59 ` Jarkko Sakkinen
2024-05-21 22:42 ` Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 5/6] tpm: tpm2_key: Extend parser to TPM_LoadableKey Jarkko Sakkinen
2024-05-21 5:47 ` [EXTERNAL] " Bharat Bhushan
[not found] ` < <SN7PR18MB53140F4341BC441C1C11586EE3EA2@SN7PR18MB5314.namprd18.prod.outlook.com>
2024-05-21 7:13 ` Jarkko Sakkinen
2024-05-21 3:16 ` [PATCH v2 6/6] keys: asymmetric: ASYMMETRIC_TPM2_KEY_RSA_SUBTYPE Jarkko Sakkinen
2024-05-21 7:25 ` [EXTERNAL] " Bharat Bhushan
[not found] ` < <SN7PR18MB531494159D3996799475209DE3EA2@SN7PR18MB5314.namprd18.prod.outlook.com>
2024-05-21 7:38 ` Jarkko Sakkinen
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