amoralej / centos / cbs-tools

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CentOS Infra lookaside upload script

This upload script is a fork of Fedora's.  The original version of the script was taken from https://git.fedorahosted.org/cgit/fedora-infrastructure.git/tree/scripts/upload.cgi (although I think that version might be a bit on the old side, but it does the job).

The script has been modified somewhat (ok, quite a lot) to fit CentOS' requirements.


Requirements:

Basic requirements from kbsingh et al:

- Users must be authenticated to be able to upload
- Authentication must be done using client SSL certificates from a private CA
- Files must be uploaded in the centos <package>/<branch>/<sha1sum> scheme, rather than the fedora scheme
- The upload process must be able to be driven from centpkg (so ideally similar script/parameters to fedora)
- Upload permissions must be controlled from the gitblit config

Some more requirements of mine:

- The upload system must check for revocation of client certs
- Client cert revocation should be done quickly (immediately if possible)


Assumptions:

- Every user who can upload has a unique username.
- Every user has an account in git.centos.org's gitblit.
- Every user has a client SSL certificate, issued by the CBS CA.
- The client SSL certificate has a CN of their username as part of the certificate subject.
- A users git username matches their koji username.


Access Control:

The script requires a user to authenticate with their client SSL cert.  All users can run the script in check mode.  If a user tries to upload, the script checks the gitblit config to ensure that the user has permissions to the package.

(This access control can be disabled using the script config file, if desired)


Apache SSL Configuration:

The following config is sufficient for the SSL client auth:

  # This needs to point to the CA cert that issued the client certs
  SSLCACertificateFile /etc/pki/tls/certs/cbs-ca.crt

  # Don't verify client certs on the server by default
  SSLVerifyClient none

  # Tell Apache the upload script is CGI
  ScriptAlias /lookaside/upload.cgi /var/www/cgi-bin/upload.cgi

  # Enable client cert verification for the upload script URL
  <Location /lookaside/upload.cgi>
          SSLVerifyClient require
          SSLVerifyDepth 1
  </Location>

Ideally we want to check for client cert revocation.  We can check a local CRL file with the following config.  Note that if the CRL is updated, Apache needs to be restarted to pick up the changes.

  # check revocation of client certs against the CRL
  SSLCARevocationCheck leaf
  # specify the CRL file location (must be in PEM format)
  SSLCARevocationFile /etc/pki/tls/certs/ipa.crl

If at some point we switch to a CA with an OCSP responder, we can use the following config (Apache 2.4 required) to do a live OCSP client cert revocation check on upload:

  # turn on OCSP checking of client certs
  SSLOCSPEnable on
  # set the URL for the OCSP responder
  SSLOCSPDefaultResponder http://my.ca.server/ca/ocsp
  # ignore the OCSP URL in client certs and use the one we configured
  SSLOCSPOverrideResponder on


Calling The Script:

Obviously, you need a valid client cert.  You then need to call the script with the right parameters.  Here's the parameters:

- name
- branch
- sha1sum
- file

name, branch, and sha1sum are mandatory.  name is the package name.  branch is the name of the branch.  sha1sum is a (lowercase) hex SHA1 checksum for the file.  If only these three parameters are provided, the script checks if there is a matching file uploaded.  If the file exists, the script returns the string "Available".  If the file does not exist, the script returns the string "Missing".

If the parameter file is passed, this parameter must be the contents of the file.  The uploaded file will be written to a temporary file, and the checksum of the file compared to the value of the sha1sum parameter.  If the sums match, the file is moved into position.

The script can be called using curl commands similar to the following.  The file mycert.pem contains the client's cert (and private key).

To upload a file (389-ds-base-1.3.1.6.tar.bz2 in the current directory):

curl --cert ./mycert.pem https://git.centos.org/lookaside/upload.cgi --form "name=389-ds-base" --form "branch=c7" --form "sha1sum=ce4e6293a996e1045bc8f75533418f3172b391ee" --form "file=@389-ds-base-1.3.1.6.tar.bz2"
File 389-ds-base-1.3.1.6.tar.bz2 size 3070988 SHA1 ce4e6293a996e1045bc8f75533418f3172b391ee stored OK

To check if a file exists:

curl --cert ./mycert.pem https://git.centos.org/lookaside/upload.cgi --form "name=389-ds-base" --form "branch=c7" --form "sha1sum=ce4e6293a996e1045bc8f75533418f3172b391ee"
Available

(on a normal end client, this would be handled by centpkg)

(centos' curl defaults to looking in a NSS db for a client cert; force the --cert arg to be a path - even a relative one like ./mycert.pem - to stop this behaviour)


Email Notification:

The script sends an email to a configured email address when a file is uploaded.  The script tries to send the mail via a configured mail relay.  By default, SELinux will block the script from connecting to port 25 on the configured mail server.  Set the httpd_can_network_connect boolean on to allow it.


Script Config File:

The upload script config file is /etc/lookaside.cfg.  There are config options for all the interesting values.  The script doesn't check the config syntax is correct, so missing / malformed values are likely to case python tracebacks.