Potential fix for code scanning alert no. 44: Incomplete regular expression for hostnames

[tlimoncelli]

Potential fix for https://github.com/StackExchange/dnscontrol/security/code-scanning/44

To fix the problem, all literal dots in the hostname portion of the regex must be escaped so they are treated as literal periods instead of “any character”. Since the base URL is held in selfLinkBasePath and then concatenated into the regex, the best approach is to escape the dots in selfLinkBasePath at construction time (while keeping / and : unescaped), so that the resulting full regex behaves as intended and still clearly expresses the expected URL prefix.

Concretely, in providers/gcloud/gcloudProvider.go, keep selfLinkBasePath as a normal string constant for use elsewhere, but when building networkURLCheck, wrap selfLinkBasePath with regexp.QuoteMeta. Then append the rest of the regex (project ID and network name parts) as before. regexp.QuoteMeta(selfLinkBasePath) will escape all regex metacharacters (including .), eliminating the over-permissive matching on the host, while preserving the intended matching of path structure and constraints on project/network names. No new imports are needed, since regexp is already imported. The only line to change is the definition of networkURLCheck.

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