From: Herbert Xu <herbert@gondor.apana.org.au>
To: wufan@kernel.org
Cc: keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com,
lukas@wunner.de, ignat@cloudflare.com, davem@davemloft.net,
jarkko@kernel.org, zohar@linux.ibm.com, eric.snowberg@oracle.com
Subject: Re: [PATCH v2] KEYS: X.509: Fix Basic Constraints CA flag parsing
Date: Sun, 28 Sep 2025 11:56:09 +0800 [thread overview]
Message-ID: <aNix2dfs0FC74Zi2@gondor.apana.org.au> (raw)
In-Reply-To: <20250915211550.2610-1-wufan@kernel.org>
On Mon, Sep 15, 2025 at 09:15:50PM +0000, wufan@kernel.org wrote:
> From: Fan Wu <wufan@kernel.org>
>
> Fix the X.509 Basic Constraints CA flag parsing to correctly handle
> the ASN.1 DER encoded structure. The parser was incorrectly treating
> the length field as the boolean value.
>
> Per RFC 5280 section 4.1, X.509 certificates must use ASN.1 DER encoding.
> According to ITU-T X.690, a DER-encoded BOOLEAN is represented as:
>
> Tag (0x01), Length (0x01), Value (0x00 for FALSE, 0xFF for TRUE)
>
> The basicConstraints extension with CA:TRUE is encoded as:
>
> SEQUENCE (0x30) | Length | BOOLEAN (0x01) | Length (0x01) | Value (0xFF)
> ^-- v[2] ^-- v[3] ^-- v[4]
>
> The parser was checking v[3] (the length field, always 0x01) instead
> of v[4] (the actual boolean value, 0xFF for TRUE in DER encoding).
>
> Also handle the case where the extension is an empty SEQUENCE (30 00),
> which is valid for CA:FALSE when the default value is omitted as
> required by DER encoding rules (X.690 section 11.5).
>
> Per ITU-T X.690-0207:
> - Section 11.5: Default values must be omitted in DER
> - Section 11.1: DER requires TRUE to be encoded as 0xFF
>
> Link: https://datatracker.ietf.org/doc/html/rfc5280
> Link: https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
> Fixes: 30eae2b037af ("KEYS: X.509: Parse Basic Constraints for CA")
> Signed-off-by: Fan Wu <wufan@kernel.org>
> ---
> crypto/asymmetric_keys/x509_cert_parser.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
prev parent reply other threads:[~2025-09-28 3:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-11 22:53 [PATCH] KEYS: X.509: Fix Basic Constraints CA flag parsing wufan
2025-09-12 13:14 ` Lukas Wunner
2025-09-12 21:14 ` Fan Wu
2025-09-13 4:38 ` Lukas Wunner
2025-09-13 5:37 ` Fan Wu
2025-09-15 21:15 ` [PATCH v2] " wufan
2025-09-16 14:52 ` Lukas Wunner
2025-09-28 3:56 ` Herbert Xu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aNix2dfs0FC74Zi2@gondor.apana.org.au \
--to=herbert@gondor.apana.org.au \
--cc=davem@davemloft.net \
--cc=dhowells@redhat.com \
--cc=eric.snowberg@oracle.com \
--cc=ignat@cloudflare.com \
--cc=jarkko@kernel.org \
--cc=keyrings@vger.kernel.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lukas@wunner.de \
--cc=wufan@kernel.org \
--cc=zohar@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).