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[Bug 1835114] Re: [MIR] ec2-instance-connect


At a high level I'm concerned about several parts of this tool's design:

- First, it puts an incredibly high level of trust in the metadata
  service. This may make sense in the context of executing on the Amazon
  platform, but is positively dangerous outside the Amazon platform. It's
  extremely risky in the event that someone's networking routes are
  incorrect on AWS -- consider a VPN that is configured to send
  and to a remote peer, in order to send *all* data elsewhere.

  This tool will directly execute anything returned from the metadata
  service with no logging or accounting or access controls.

  This is far beyond what users may reasonably expect: that this would
  manage authorized_keys and nothing else.

  The pervasive use of eval is inappropriate.

- Second, this is implemented in shell and is beyond the complexity level
  appropriate to shell. Many of the commands in shell pipelines could
  fail without the scripts noticing.

  (It's a significantly smaller point, but the CPU and disk use of this
  tool would be larger than a purpose-built executable in a higher-level
  language like Go, Python, etc.)

- Third, this is re-implementing much of the functionality of the OpenSSH
  certificate support introduced in 2010. What features does this provide
  that's not present in OpenSSH already?

- Fourth, shellcheck found many issues, most of which deserve to be fixed.
  There's repeated instances of missing "" quotes around variables.

Some of the issues in the programs:

- Incorrect use of printf in eic_harvest_hostkeys -- variables interpolated
  into the format string.

- eic_harvest_hostkeys uses eval for string to number conversion, rather
  than using string comparisons

- eic_harvest_hostkeys uses eval to execute something straight from the
  metadata service

- what does awk '{$1=$1};1' do? Why use cat? This should work: key="$(<

- what's the point of unsetting environment variables when bash is

- eic_parse_authorized_keys uses CN string comparisons -- why? Is this a
  useful security control? If the openssl command fails entirely, the CN
  string check is bypassed. Is this a problem?

- eic_parse_authorized_keys appears to use $tmpdir extensively but if none
  is given on the command line, it does not fail. Probably its behaviour
  if -d tmpdir is forgotten will be poor. There's no trap to clean up
  temporary files or directories on unexpected exits.

- eic_parse_authorized_keys: if CN contains \r \n \t \v whitespace tokens can
  be inserted into future commands lines via use of 'echo'. Other escape
  sequences may have other consequences.

- eic_parse_authorized_keys use of hardcoded /tmp/sigline is a security
  vulnerability on kernels without protected symlinks support.

- eic_parse_authorized_keys doesn't check if fingerprint's commands

- eic_parse_authorized_keys doesn't have else clauses if the base64 or the
  openssl dgst commands don't work

- eic_curl_authorized_keys uses eval for string to number conversion

- eic_curl_authorized_keys uses eval to execute something straight from
  metadata service

- eic_curl_authorized_keys unused variables: signerkeyfile keysfile

- eic_curl_authorized_keys calling into $DIR/eic_parse_authorized_keys
  with the complicated mechanism to pass openssl commands, tmpdir, etc
  looks very brittle and prone to error under maintenance

And some issues in the packaging:

- Why does the preinst install a user? I don't believe I saw it used

- prerm could skip the ls -A check and run
  rmdir --ignore-fail-on-non-empty /lib/systemd/system/ssh.service.d

This program has grown beyond what's appropriate for shell scripts.

Furthermore, I believe OpenSSH certificates is the better solution to the
problem that this program is addressing.

I strongly recommend using the OpenSSH certificates instead.

I don't believe that we should ship this package with Ubuntu.


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  [MIR] ec2-instance-connect

Status in ec2-instance-connect package in Ubuntu:

Bug description:
  ec2-instance-connect is in the Ubuntu archive, and available for all supported
  releases. It is available on all architectures despite only being useful on
  Amazon EC2 instances.

  This package is useful on Amazon EC2 instances to make use of a new feature:
  Instance Connect; which allows storing SSH keys for access online in the Amazon
  systems. These SSH keys are then retrieved to be used by the system's SSH
  service, collated with pre-existing keys as deployed on the system.

  Installing the package enables the use of Instance Connect on an

  This is a new package, and as such has no security history to speak of.

  [Quality Assurance]
  The package consists in a few shell scripts that are difficult to test by
  themselves due to the high reliance on Amazon's Instance Connect service;
  which is online and limited to use on Amazon instances.

  Given that it's a new package, there are no long-term outstanding bugs in
  Ubuntu or Debian. The package is only maintained in Ubuntu at the moment.

  This package deals with special "hardware"; it is only useful on Amazon
  instances, and its support is required as a default deployment on such
  instances when deployed with Ubuntu.

  [UI Standards]
  Not applicable. This service is command-line only and has no configuration options.

  There are no special dependencies to speak of.

  [Standards Compliance]
  This package has been thoroughly reviewed by a few Canonical engineers, there
  are no standards violations known.

  This package is to be owned by the Ubuntu Foundations team.

  [Background Information]
  This is Amazon-specific, as previously mentioned.

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