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[cherry-pick] Avoid dangling symlinks in git-init #3485

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merged 1 commit into from
Nov 2, 2020

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@vdemeester vdemeester commented Nov 2, 2020

When the following conditions are met:

  1. the feature flag disable-home-env-overwrite is "true"
  2. the container user is root
  3. no git / ssh secret is attached to a taskrun service account
  4. user is running new-ish version of catalog git-clone task with git-init v0.15.2+

git-init will error out in the git-clone task because we create a circular symlink
from /root/.ssh to itself and then try to look up /root/.ssh/known_hosts.

This commit adds a check to avoid this from happening:

If the user's $HOME/.ssh directory doesn't exist or if they aren't able to access it
for any reason, then we don't try to create a symlink to it at all since we can trust that
the user is incapable of utilizing the credential.

This commit also expands an existing check to see if the $HOME/.ssh directory is
the same as the user's home directory + '.ssh'. This was originally only checked if
the user was nonroot, but now this is also checked if the user is root too.

(cherry picked from commit 1160686)
Signed-off-by: Vincent Demeester [email protected]

/kind bug
/cc @sbwsg @bobcatfish @afrittoli

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Release Notes

Fixed a bug in `git-init` that allowed a circular symlink to be created from `/root/.ssh` to itself if no SSH credentials are present in the service account and the `disable-home-env-overwrite` flag is set to `"true"`.

When the following conditions are met:

1. the feature flag disable-home-env-overwrite is "true"
2. the container user is root
3. no git / ssh secret is attached to a taskrun service account
4. user is running new-ish version of catalog git-clone task with git-init v0.15.2+

git-init will error out in the git-clone task because we create a circular symlink
from /root/.ssh to itself and then try to look up /root/.ssh/known_hosts.

This commit adds a check to avoid this from happening:

If the user's $HOME/.ssh directory doesn't exist or if they aren't able to access it
for any reason, then we don't try to create a symlink to it at all since we can trust that
the user is incapable of utilizing the credential.

This commit also expands an existing check to see if the $HOME/.ssh directory is
the same as the user's home directory + '.ssh'. This was originally only checked if
the user was nonroot, but now this is also checked if the user is root too.

(cherry picked from commit 1160686)
Signed-off-by: Vincent Demeester <[email protected]>
@tekton-robot tekton-robot requested review from afrittoli, bobcatfish and a user November 2, 2020 13:38
@tekton-robot tekton-robot added release-note Denotes a PR that will be considered when it comes time to generate release notes. kind/bug Categorizes issue or PR as related to a bug. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Nov 2, 2020
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The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File Old Coverage New Coverage Delta
pkg/git/git.go 2.4% 2.3% -0.1

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbwsg

The full list of commands accepted by this bot can be found here.

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ghost commented Nov 2, 2020

/lgtm

@tekton-robot tekton-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Nov 2, 2020
@tekton-robot tekton-robot assigned ghost Nov 2, 2020
@tekton-robot tekton-robot added the lgtm Indicates that a PR is ready to be merged. label Nov 2, 2020
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/retest

@tekton-robot tekton-robot merged commit 20672ac into tektoncd:release-v0.17.x Nov 2, 2020
@vdemeester vdemeester deleted the cherry-pick-3346 branch November 2, 2020 15:03
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