Issues with the Base64 encoding zero fill padding pattern

Using Arduino Programming Questions
1

I got some issues with the zero fill patterns on an Arduino esp32 skatch for a rest server. I want to use the basic HTTP authentification header, but the base64 encoder that i've found for Arduino esp32 use a different pattern ('A' instead of '=' and 'A=' instead of '==').
Did someone know a library that use the same specs as the oldschool HTTP authentification?
Or knows a solution without aditional workaround? Because that is superfluous if the encoder can be implemented with the required specifications.

2

I've used this Base64 library in the past for encoding binary as printable text. A quick look at the source code suggests that it uses '='. My project was for a different purpose than HTTP but the library may be what you are looking for.

3

Thanks, I will embed it and try it out. :slight_smile:

4

Unfortunately it was taken from the same code base and the code in lines 55 to 69 is a bit confused:

55  if(i){
56          for(uint8_t j = i; j < 3; j++){
57              a3[j] = '\0';
58          }
59  
60          a3to4(a3, a4);
61  
62          for(uint8_t j = 0; j < i + 1; j++){
63              *output++ = alphaTable[a4[j]];
64          }
65  
66          while(i++ < 3){
67              *output++ = '=';
68          }
69      }
72  }

Fullfilling a3 with zeros (in lines 56 to 58) results in some useless 'A's being added to the output.
(alphaTable[0] = 0x41 = 65 = ASCII index for A).
This is because that increasing by 1 in line 62 results in an addition of surely one 'A' - in some cases two 'A's - to the output.
The padding with equal signs, which is actually exclusively required, is additionally executed (lines 66 to 69).

User: 'admin', password: 'esp32'
www-authorization: 'basic YWRtaW46ZXNwMzI='
BASE64::encode generates 'YWRtaW46ZXNwMzIA'

User: 'admin', password: 'esp3'
www-authorization: 'basic YWRtaW46ZXNwMw=='
BASE64::encode generates 'YWRtaW46ZXNwMwA='

User: 'admin', password: 'esp'
www-authorization: 'basic YWRtaW46ZXNw'
BASE64::encode generates 'YWRtaW46ZXNwAA=='

5

This looks like it was done right:

But it's a pure C++ library...

6

Since I have not found an Arduino Base64 [en|de]coder, which coding standard Base64 strings, can be integrated out of the box and meets my ideas of lightweight, I scripted a new lib:

7

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