CatchAsCatchCan's questions -ubuntu

CatchAsCatchCan

Asked: 2019-03-21 12:13:18 +0800 CST

DKIM failure 'body hash did not verify', but only on CRON output

I have successfully installed Postfix and OpenDkim on my server, and it's correctly signing mail from several different domains. The host we'll call webhost.example.com. It's running Ubuntu 18.04.2 LTS, Postfix 3.3.0 and OpenDKIM v2.11.0

Today I wanted to get output from some CRON jobs sent to my Gmail account so I set up the required entries in the KeyTable and SigningTable and generated the keys and tested it with a one line email to myself.

echo "Test message" | mail -s "Test message" [email protected]

This should generate an email from [email protected]. It does, correctly signed by OpenDKIM, and delivered to my Gmail account where it successfully passes validation.

Here's what I get at GMail:

Received-SPF: pass (google.com: domain of [email protected] designates 13.238.180.128 as permitted sender) client-ip=13.238.180.128;
Subject: This is a test message
To: <[email protected]>
Message-Id: <[email protected]>
Date: Wed, 20 Mar 2019 04:00:36 +0000 (UTC)
From: Ubuntu <[email protected]>

This is a test message. You know the drill!

So far, so good.

I set up my cron jobs and add the line

[email protected]

The output is generated, signed and mailed, but GMail fails the DKIM validation with

dkim=neutral (body hash did not verify) [email protected] header.s=webhost header.b=tXJM8ih0;

Here's the complete email. If it's useful this is output from a curl request.

Delivered-To: [email protected]
Received: by 2002:a5d:48c4:0:0:0:0:0 with SMTP id p4csp776152wrs;
        Wed, 20 Mar 2019 07:14:04 -0700 (PDT)
X-Google-Smtp-Source: APXvYqyZdMJuwpApjkjfxfh/rsHg67hLBtQSS5j0BUCq8NaaxUqV+sIDf7CPy+sYjS2b817v9pAu
X-Received: by 2002:a63:5541:: with SMTP id f1mr7627593pgm.38.1553091244323;
        Wed, 20 Mar 2019 07:14:04 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; t=1553091244; cv=none;
        d=google.com; s=arc-20160816;
        b=h3SPkfLIm9BjWS+SlJc4Wd/8XFE2YT3QNSOkzzLY858wldyOXMn3OR8rFcU6UVmbEL
         stCPHuXM7ouP0s7ICTC4TAyv+DiqWNokBsRkwXjdP6+mEEmXlP6VUk8H/+nL89BrMp4E
         FhzVM4sE5/3VphjuXPom0Ux+e+WrLDWBZbKMbMOLSMkbmCL6B3/llK3FMwPfAGPzS2O8
         o+cfm6r15W0aND02eIvNg6px2kNmD+wHAI993/BZJ3vIPvNzsEHFUWwbD10iYkIUwmvA
         DMUVB3jx+pXtFhv17+Fpx0zsSx5806vieOVoLxXAnlJgdykNH/DuZY3NM1DVyR1Renxw
         eTPg==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=date:message-id:content-transfer-encoding:mime-version:subject:to
         :from:dkim-signature;
        bh=lkMik4Dz2hOPxvMLwTHlE8QE1l4G/X7DcjAYikPMEMc=;
        b=N85+olM3406vk7LhpV03QNxCZQLELh+ZLjUIUg1xt5u7z/aJZS0CRa1q4JJcBn8Fm0
         nRBvMLFJXIrm0Y11s5kET6Xvzkk9G/szfJNqthy7e80mHs2Q7xgfYeVpYmQmL3DxjVjm
         mzlnJVzVyx0XLMcAKaneb0CkOIsuOo6nkCGMakPsS9e+vMpfdnBggZZQv1zqkGHzTnML
         +QMIVMEH7kgQphYo6GiCVb1LWThuwYyI+nSclPDw9fNLRPGTNqbiBqWQuEdgM3/K46Zy
         gY4SgTXwL+MOCVgIbN33ZG3FuVHwyr5bQZGrpR48HXS68zYA5jbcgF9eFDBtuBOQPDo+
         HkKw==
ARC-Authentication-Results: i=1; mx.google.com;
       dkim=neutral (body hash did not verify) [email protected] header.s=webhost header.b=tXJM8ih0;
       spf=pass (google.com: domain of [email protected] designates 13.238.180.128 as permitted sender) [email protected];
       dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=example.com
Return-Path: <[email protected]>
Received: from webhost.example.com (ec2-13-238-180-128.ap-southeast-2.compute.amazonaws.com. [13.238.180.128])
        by mx.google.com with ESMTP id b7si1705816pgl.20.2019.03.20.07.14.03
        for <[email protected]>;
        Wed, 20 Mar 2019 07:14:04 -0700 (PDT)
Received-SPF: pass (google.com: domain of [email protected] designates 13.238.180.128 as permitted sender) client-ip=13.238.180.128;
Authentication-Results: mx.google.com;
       dkim=neutral (body hash did not verify) [email protected] header.s=webhost header.b=tXJM8ih0;
       spf=pass (google.com: domain of [email protected] designates 13.238.180.128 as permitted sender) [email protected];
       dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=example.com
Received: by webhost.example.com (Postfix, from userid 1000)
    id 0FACCFA104; Wed, 20 Mar 2019 14:14:02 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;
    d=webhost.example.com; s=webhost; t=1553091242;
    bh=20rEKrmO1yPqlIJwX4HLsjr/kx4SaM/AaK17/OmPhLA=;
    h=From:To:Subject:Date:From;
    b=tXJM8ih006AjxwXJNAD30k7Fjo/HYTsi5bEfOCaxr0D8BiEAA/mIiDvaexjHPWNQ6
     B5DrCGlhvLVZIRs1Zp2v4pbYYYvpmrzOTB99vXk0lEEGTRIwdhvAYKT31Jt2N5VMq3
     hifps7hj3TD/Eevks82VvcIu2xJWXFPNEZMGvjcRa3hFSE2IIcfOhMJhwX5Rcnx+F4
     wjtxqROgxXpHxgJkXzkVe3HbpKVK5eOrsBoeRnUhR4SWa2f7UKhT4k28KOuTQo8bG3
     E63PoPwcOQU4cPiiqnPEdWO7ERvSHetgh/1yjpigcbch9SWwQHwA4FPSmcfOfLeIov
     +wxrbVKHXtzMA==
From: [email protected] (Cron Daemon)
To: [email protected]
Subject: Cron <ubuntu@webhost> curl https://invoicing2018.example.com/tasks/run
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-Cron-Env: <[email protected]>
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/home/ubuntu>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=ubuntu>
Message-Id: <[email protected]>
Date: Wed, 20 Mar 2019 14:14:02 +0000 (UTC)

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

The emails from cron also fail the Port25 verifier in the same way

So, the question is:

Why does my DKIM configuration correctly sign everything but output from CRON?

What can I do to fix this?

I could try using a script to run the curl request and send the email with mail, but I have a number of other cron jobs to add yet and I'd rather fix the underlying problem before trying work-arounds.

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