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Basically a place that Chris can post solutions to problems so he can easily find them later

cjhaas blog

Basically a place that Chris can post solutions to problems so he can easily find them later

curl with base64 encoded data

Posted on November 26, 2014 By [email protected]

I just spent the last hour trying to figure out how to send base64 encoded data that lives in a file using curl. Everyone says to just use --data-binary but that assumes you know what the binary format should actually be! Every combination I tried of --data-ascii and --crlf kept failing with server-side errors.

The trick for me was making sure that the file itself was manually URL encoded. So all newlines were replaced with %0a and all plus signs were replaced with %2b. Then just put everything on one line. So my file (which was a SAML payload for testing) looked like:

                                                                 +                     \n
SAMLResponse=PZXhXN0iSxR3Lklvbd3dlGjpNaW5hdGlWWxbj0wb20aYyb25zZSB%2bi5jFYWRpdHwMv0vZ28v%0acG5zZT4=

This can just be sent using the normal --data parameter as a file:

curl -XPOST --data @saml.txt http://www.example.net/
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Comments (2)

  1. Martin K. says:
    December 11, 2019 at 6:15 am

    Thanks for sharing this way. I was struggeling while POSTing data with special chars (#;?$&) using a script (cygwin).

    I thougt about “sending the data as base64-encoded string” and found this site. I was thinking to do something like ” –data ‘[base64-encoded-content]’ ” but the webserver did not undetstand my data (was not decoding the base64 to plain text).

    So I did “your trick” to save the data in a separate file and POSTed it with ” –data @plaintextfile.txt ” … it worked.

    Thanks again for sharin your way!

    Martin

    Reply
  2. Binayak says:
    February 3, 2020 at 8:03 pm

    Using ‘–data-ascii’ with -H ‘Content-Type: text/plain’ worked for me.

    Reply

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