Flow Designer with Rest step using Basic Authentication produces generic error

[#1]

I am trying to use the Flow Designer Integration for REST and using an credential alias to invoke a Basic Authentication request.  I get a generic  {"Message":"An error has occurred."}.

I think I am having a fundamental missunderstanding how to pass the Basic Authentication credential in the header where the username :  password from the credential is 64BitEncoded.

Here is my setup...what am I doing wrong?

[#2 · Accepted solution]

Turns out I did not need the header row with the authentication specified...but more importantly, the credential record for basic authentication has a character limit of 40 which was cutting off my username.  Once I adjusted the limit to 80 characters the process went through as expected.

[Petr Pastuszek1]

Hello,
I had a similar issue.
In Flow Designer, the REST Step to run REST message requires to provide connection and credential aliases as of basic authentication.
Once I have completed this step and imported REST message in REST Step, I got all the time response code 400 back.
Several hours I tried to debug and at the end I found this.

Basic authentication require user name / password
user name field is max size 40
SUpplier provided me with user name long 48 characters.
I increased field size and updated basic authentication record with the full user name again.
All started to work.

PS: What helped was to run REST via background script and than I compared HTTP outbound log with HHTP outbound log created by REST called from flow designer, string of Authentication value form HTTP header started to be the same but after 50 characters changes which helped me to understand and debug this field max size issue.

Hope this post helps to someone

/Petr