The template validation method in the heat API allows to specify the
template to validate using a URL with the 'template_url' parameter.
By entering invalid http URLs, like 'http://localhost:22' it is
possible to scan ports by evaluating the error message of the request.
For example, the request
curl -H "Content-Type: application/json" -H "X-Auth-Token: <TOKEN>" \
-X POST -d '{"template_url": "http://localhost:22"}' \
http://127.0.0.1:8004/v1/<TENANT_ID>/validate
causes the following error message to be returned to the user:
"Could not retrieve template: Failed to retrieve template:
('Connection aborted.',
BadStatusLine('SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1\\r\\n',))"
This could be misused by tenants to gain knowledge about the internal
network the heat API runs in.
To prevent this information leak, this patch alters the error message
to not include such details when the url scheme is not 'file'.
SecurityImpact
Closes-Bug: #1606500
Change-Id: Id1f86f41c1e6c028d889eca7ccbb9cde67631950
eab9a33ce7