[azure-storage-blob] wrong sas permission string caused authentication failure

[Juliehzl]

• Package Name: azure-stroage-blob
• Package Version: 12.4.0b1
• Operating System: Win 10
• Python Version: 3.7.7

Describe the bug
A clear and concise description of what the bug is.
When specify permission with string, it passes the permission string to _str as shown here:

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_models.py

Line 930 in 1216acf

parsed._str = permission # pylint: disable = protected-access

but what we expect is that it should be format with the following method:

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_models.py

Lines 899 to 904 in 1216acf

	self._str = (('r' if self.read else '') +
	('w' if self.write else '') +
	('d' if self.delete else '') +
	('x' if self.delete_previous_version else '') +
	('l' if self.list else '') +
	('t' if self.tag else ''))

If the permission string sequence changes, it will cause signed signature change and authentication failure.

Removing this line could fix it.

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_models.py

Line 930 in 1216acf

parsed._str = permission # pylint: disable = protected-access

Same for other sas permissions.

To Reproduce
Steps to reproduce the behavior:

1. generate sas token with specifying container sas permission with string like 'dlrw'
2. upload blob with generated sas

but if you are using rwdl, it will work.

Expected behavior
A clear and concise description of what you expected to happen.

Authentication failed.

Screenshots
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Additional context
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[xiafu-msft]

This will be addressed in the pr, thanks for catching this!

[tasherif-msft]

Hi @Juliehzl, the PR related to this issue has been merged. I will proceed to close this issue. Let us know if anything else comes up!