From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id AA45A933B9 for ; Mon, 19 Feb 2024 17:11:41 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 8316832C57 for ; Mon, 19 Feb 2024 17:11:11 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for ; Mon, 19 Feb 2024 17:11:11 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id C9BAA4381E for ; Mon, 19 Feb 2024 17:11:10 +0100 (CET) Message-ID: <29e05069-547e-46a5-9ed2-befbfbe0e4b5@proxmox.com> Date: Mon, 19 Feb 2024 17:11:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: pbs-devel@lists.proxmox.com References: <20240215152001.269490-1-s.sterz@proxmox.com> <20240215152001.269490-7-s.sterz@proxmox.com> From: Max Carrara In-Reply-To: <20240215152001.269490-7-s.sterz@proxmox.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SPAM-LEVEL: Spam detection results: 0 AWL -0.006 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: Re: [pbs-devel] [PATCH proxmox 06/12] sys: crypt: use constant time comparison for password verification X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Feb 2024 16:11:41 -0000 On 2/15/24 16:19, Stefan Sterz wrote: > by using `openssl::memcmp::eq()` we can avoid potential timing side > channels as its runtime only depends on the length of the arrays, not > the contents. this requires the two arrays to have the same length, but > that should be a given since the hashes should always have the same > length. > > Signed-off-by: Stefan Sterz See my reply to patch 04 - the usage of `openssl::memcmp::eq()` in the legacy code block there could be merged with this commit first before moving to / implementing HMAC. LGTM otherwise, but see the comment inline. > --- > proxmox-sys/Cargo.toml | 3 ++- > proxmox-sys/src/crypt.rs | 8 +++++++- > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/proxmox-sys/Cargo.toml b/proxmox-sys/Cargo.toml > index 5ddbe21..1a44702 100644 > --- a/proxmox-sys/Cargo.toml > +++ b/proxmox-sys/Cargo.toml > @@ -16,6 +16,7 @@ lazy_static.workspace = true > libc.workspace = true > log.workspace = true > nix.workspace = true > +openssl = { workspace = true, optional = true } > regex.workspace = true > serde_json.workspace = true > serde = { workspace = true, features = [ "derive" ] } > @@ -29,5 +30,5 @@ proxmox-time.workspace = true > default = [] > logrotate = ["dep:zstd"] > acl = [] > -crypt = [] > +crypt = ["dep:openssl"] > timer = [] > diff --git a/proxmox-sys/src/crypt.rs b/proxmox-sys/src/crypt.rs > index fa10911..3313f66 100644 > --- a/proxmox-sys/src/crypt.rs > +++ b/proxmox-sys/src/crypt.rs > @@ -155,9 +155,15 @@ pub fn encrypt_pw(password: &str) -> Result { > /// Verify if an encrypted password matches > pub fn verify_crypt_pw(password: &str, enc_password: &str) -> Result<(), Error> { > let verify = crypt(password.as_bytes(), enc_password.as_bytes())?; > - if verify != enc_password { > + > + // `openssl::memcmp::eq()`'s runtime does not depend on the content of the arrays only the > + // length, this makes it harder to exploit timing side-channels. > + if verify.len() != enc_password.len() > + || !openssl::memcmp::eq(verify.as_bytes(), enc_password.as_bytes()) Like in my comment on patch 04, would it make sense here to split these checks into two for more fine-grained error messaging? Or are there any reasons why they should be together? > + { > bail!("invalid credentials"); > } > + > Ok(()) > } >