From: "Maciej S. Szmigiero" Subject: Re: [PATCH v2] X.509: unpack RSA signatureValue field from BIT STRING Date: Tue, 17 Apr 2018 17:11:54 +0200 Message-ID: <7497a6f6-b9fc-a249-a6c8-42ff2723aa4a@maciej.szmigiero.name> References: <6f5cdb8a-809e-6651-0e32-711d415a8b38@maciej.szmigiero.name> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Cc: David Howells , Herbert Xu , "David S. Miller" , Tom Lendacky , Gary Hook , James Morris , "Serge E. Hallyn" , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org To: Kamil Konieczny Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On 17.04.2018 17:07, Kamil Konieczny wrote: > > > On 17.04.2018 15:39, Maciej S. Szmigiero wrote: >> The signatureValue field of a X.509 certificate is encoded as a BIT STRING. >> For RSA signatures this BIT STRING is of so-called primitive subtype, which >> contains a u8 prefix indicating a count of unused bits in the encoding. >> >> We have to strip this prefix from signature data, just as we already do for >> key data in x509_extract_key_data() function. >> >> This wasn't noticed earlier because this prefix byte is zero for RSA key >> sizes divisible by 8. Since BIT STRING is a big-endian encoding adding zero >> prefixes has no bearing on its value. >> >> The signature length, however was incorrect, which is a problem for RSA >> implementations that need it to be exactly correct (like AMD CCP). >> >> Signed-off-by: Maciej S. Szmigiero > > your e-mail address looks incorrect > > [...] > What's wrong with it? Maciej