Long Refactoring: More loop cleanup

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In my last article on the Long Refactoring series, I elided the process I went through to solve the bug. While preparing to turn the articles into a presentation, I went through the steps myself again, and came across the bug. When I was writing the articles, I was pressed for time, and didn’t go through the process of solving it step by step, which in turn means there is a gap between the pre-and-post states of the code: you can’t get there from here.
Let me take it from where I mentioned that I found a bug, and added the unit test that shows it.

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FreeIPA: whoami via curl

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Assuming PRINCIPAL is your Kerberos principal and $IPASERVER is the FQDN of your server, you can query your identity on the IPA server via curl:

kinit $PRINCIPAL
curl -k -H referer:https://$IPASERVER/ipa   -H "Content-Type:application/json"    -H "Accept:applicaton/json"   --negotiate -u :   --cacert /etc/ipa/ca.crt   -d  '{"method":"whoami","params":[[],{"version": "2.220"}],"id":0}'   -X POST    https://$IPASERVER/ipa/json
{"result": {"object": "user", "command": "user_show/1", "arguments": ["ayoung"]}, "version": "4.5.4", "error": null, "id": 0, "principal": "ayoung@YOUNGLOGIC.COM"}

This is handy if your system is not registered as an IPA client.

To fetch by username:

curl -k -H referer:https://$IPASERVER/ipa   -H "Content-Type:application/json"    -H "Accept:applicaton/json" --negotiate -u : --cacert /etc/ipa/ca.crt -d '{"method": "user_show", "params": [[ "ayoung" ], { "all": true, "rights": true }  ]}'  -X POST    https://$IPASERVER/ipa/json

Scoped versus unscoped RBAC

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Role Based Access Control (RBAC) as defined by NIST is based on the concept of global roles. Global, in this case, means the scope of the application. So if you have the role of ADMIN, and you are in a globally scoped RBAC based application, that role applies to all APIs and resources within the program.

OpenStack was written assuming that the ADMIN role was a global role. But then it was implemented as a non-global role. It was implemented as a role scoped to a tenant. The term tenant was the original (and I would argue, better) term for what was later called Project, and then again expanded to Domains as well.

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Fetching all packages from a Koji build

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#bin/bash

KOJI_URL=https://kojipkgs.fedoraproject.org/packages/kernel/6.12.0/0.rc3.20241015giteca631b8fe80.32.eln143/aarch64/ 

curl $KOJI_URL > aarch64.dir.html
for  PACKAGE in  `xmllint --html  --xpath "//html/body/pre/a/@href" aarch64.dir.html | awk -F\" 'NR % 2 == 0 { print $2 }' `;  
do 
        URL=$KOJI_URL/$PACKAGE ;
        echo $URL; wget $URL;
done

Modify the URL to fetch a different architecture, version, or package.

The version of xmllint I am running does not support fn:string. If it did, the “for PACKAGE” line can be redone as:

for  PACKAGE in  `xmllint --html  --xpath "string(//html/body/pre/a/@href)" aarch64.dir.html` ;

The development cycle

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how to clean up code.

  • run your code to make sure it works
  • while (work_to_do){
  • make a small change
  • test it
  • commit to git
  • }
  • push to git server on local branch
  • try it on another machine
  • collapse git commits for code review
  • test
  • post for code review

How to add a new feature

  • run your code make sure it works
  • while (work_to_do){
  • write a small test
  • while (test doesn’t pass){
    • make a small change
    • test it
    • }
  • commit to git
  • }
  • push to git server on local branch
  • try it on another machine
  • collapse git commits for code review
  • test
  • post for code review

Parsing a yum repo with XPath

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https://gnome.pages.gitlab.gnome.org/libxml2/xmllint.htmlLets say you want to see what src RPMs are in a given yum repo. If the author used createrepo to create the yum repo, it should be an a fairly standard layout. The following xpath query should pull it out.

Note that you can get xmllint to run the xpath query from libxml2


curl http://$yumserver/$somerepo/ > repo.html
xmllint --html  --xpath "//html/body/table/tr/td/a/@href" repo.html | grep src

The portion of the query a/@href will match a tag like this

<a href="https://blam.src.rpm">