Fix the string to sign

[cl-k-takahashi]

The CloudStack management server signs lower-cased users' requests.
urllib.quote_plus() encodes characters into upper case hex string, so we need to call lower() at last.

[DaanHoogland]

@cl-k-takahashi : please explain your point. As I tried to reproduce what I understand from it, I got:

$ python
Python 2.7.15 (default, Feb 12 2019, 11:00:12)
[GCC 4.2.1 Compatible Apple LLVM 10.0.0 (clang-1000.11.45.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib;
>>> urllib.quote_plus("aAbBcC")
'aAbBcC'
>>> urllib.quote_plus("abc")
'abc'
>>> urllib.quote_plus("ABC")
'ABC'

I think, if we are correcting the developers documentation we need to be more expicit about the pitfall you are describing. Is this a version issue?
Please correct my understanding.

[cl-k-takahashi]

@DaanHoogland
Current CloudStack contains the code below in ApiServer.java:

 unsignedRequest = unsignedRequest.toLowerCase();

            final Mac mac = Mac.getInstance("HmacSHA1");
            final SecretKeySpec keySpec = new SecretKeySpec(secretKey.getBytes(), "HmacSHA1");
            mac.init(keySpec);
            mac.update(unsignedRequest.getBytes());

As you can see, CloudStack generates hash for lower cased request.
Current documentation is not problematic for [a-zA-Z0-9] but is problematic for urlencoded characters:

>>> urllib.quote_plus('aBcDe'.lower())
'abcde'
>>> urllib.quote_plus('aBcDe').lower()
'abcde'
>>> urllib.quote_plus('aBcDe★'.lower())
'abcde%E2%98%85'
>>> urllib.quote_plus('aBcDe★').lower()
'abcde%e2%98%85'

The 3rd result contains upper-case characters which causes verification failure in CloudStack management server.

[rohityadavcloud]

For reference, this is how cloudmonkey (python version) does it: https://github.com/apache/cloudstack-cloudmonkey/blob/5.3/cloudmonkey/requester.py#L203

[DaanHoogland]

@cl-k-takahashi very clear, thank you.