Wise Monks,

I know that in a Perl string the 0x0 character has no special meaning (unlike C) and so one can mix binary data (range 0-255, i.e. it may contain 0x0) with a "normal printed" string (i.e. with chars in 1-127) and unicode strings. So, the following will work(?):

my $str = "hello"; # no special chars, 1-127
my $sha256 = Digest::SHA::sha256("abc123"); # bytes 0-255
my $hmac = Digest::SHA::hmac_sha512("a message", "a key"); # bytes 0-2
+55
# edit, the following is mangled by PM's editor, imagine greek letters
+ here:
my $unicode_string = "αβγαabc123"; # unicode chars
+ mixed with lower-ascii
my $buffer = ""; # buffer to concatenate above into and POST them
for($str, $sha256, $hmac, $unicode_string){
  $buffer .= Encode::encode("UTF-8", $_);
}
my $b64 = base64_encode($buffer);
my $HTTPheader = "ABC: $b64";
$ua->POST("aurl" ... $b64 ... $HTTPheader ...);
$ua->GET("aurl" ... $b64 ... $HTTPheader ...);
$ua->POST("aurl" ... $buffer ... $HTTPheader ...);
$ua->GET("aurl" ... $buffer ... $HTTPheader ...);
$ua->GET("aurl" ... $unicode_string ... $HTTPheader ...);

[download]

1) Is this the correct way to do this?

2) Also, I have a question about why I need to encode in "UTF-8". Does that make sure that the "double-bytes" and possible "single-bytes" are all becoming a stream of "single-bytes"?

3) How do I treat the $buffer, in Perl, before I do a POST and GET, assuming the receiver is liberal in what it accepts? Obviously a base64 is safe but under what conditions can I send $unicode_string as is. Will sending $buffer (as is, after treated with Encode) work?

4) Is Encode::encode("UTF-8", $sha256) altering my binary data? Is it harmful on strings with binary data?

(please correct my terminology and feel free to correct it, I tried to avoid encodings for too long - note also that I am trying to find the safe way to do things when strings are mixed, i don't have a particular requirement)

EDIT: Actually, I am trying to translate some python code into Perl (see https://docs.kraken.com/rest/#section/Authentication/Headers-and-Signature):

    postdata = urllib.parse.urlencode(data)
    encoded = (str(data['nonce']) + postdata).encode()
    message = urlpath.encode() + hashlib.sha256(encoded).digest()

[download]

And (@haj) I wanted to mix binary and non-binary strings like they do in message. I ended up with:

my $postdata = Encode::encode('UTF-8', "x=1&y=2&z=greektext"); # for e
+xample, 
my $p1 = "$nonsense".'&'.$postdata; # yes & needed
my $p1_utf8 = Encode::encode_utf8($p1);
my $api_sha256 = Digest::SHA::sha256($p1_utf8);
my $message = Encode::encode_utf8($api_path)
  . Encode::encode_utf8($api_method)
  . $api_sha256; #<< last one is binary

# ... and post after some more massaging

[download]

bw, bliako

In reply to Perl strings questions by bliako

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