How to use credentials from git-credential helper #4873

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1. ethomson commented on Oct 31, 2018

   

   ethomson

   on Oct 31, 2018

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   As you've noted, this isn't something that we have built-in support for - we don't exec programs directly for a plurality of reasons. But indeed, it should be relatively straightforward to call out to the git credential fill command from a credential callback.

   We do have an example of credential callbacks but we don't have an example for one that exec's something.
2. jeroen commented on Oct 31, 2018

   

   jeroen

   on Oct 31, 2018

   Last edited by jeroen

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   So for future reference, to get credentials from e.g. github.com the callback needs to invoke a shell command equivalent to this:

   printf "protocol=https\nhost=github.com\n" | git credential fill

   If credential for the given host is stored, those are returned, and otherwise the user is prompted for a username/password. The output is then printed to stdout like this:

   protocol=https
   host=github.com
   username=jerry
   password=2aae6c35c94fcfb415dbe95f408b9ce91ee846ed
   

   Which you can then feed back to git_cred_userpass_plaintext_new in the callback.

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3. csware commented on Jan 3, 2019

   

   csware

   on Jan 3, 2019

   Last edited by csware

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   I already wrote a (GPLed) framework executing external commands from libgit2 (for filters and ssh; cf. https://gitlab.com/tortoisegit/tortoisegit/tree/master/src/libgit2). I haven't found the time for extending it for the credential API, yet, but I'm open for contributions.
4. tiennou

   added

   feature

   on Jan 29, 2019
5. connorjak commented on Oct 16, 2024

   

   connorjak

   on Oct 16, 2024

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   So for future reference, to get credentials from e.g. github.com the callback needs to invoke a shell command equivalent to this:

   printf "protocol=https\nhost=github.com\n" | git credential fill

   If credential for the given host is stored, those are returned, and otherwise the user is prompted for a username/password. The output is then printed to stdout like this:

   protocol=https
   host=github.com
   username=jerry
   password=2aae6c35c94fcfb415dbe95f408b9ce91ee846ed
   

   Which you can then feed back to git_cred_userpass_plaintext_new in the callback.

   To adapt this to a windows C/C++ environment, I needed to use _popen("git credential fill < temp_file.txt", "r"), which opens a pipe to read the stdout output of git credential fill. The temp_file.txt was previously populated with

   protocol=https
   host=github.com
   
   

   The reason I used a file instead of piping it in on the command line is passing input and reading output on the same pipe is not possible. The output string was constructed by reading from the pipe using fgets. Don't forget _pclose() as well.