Trimming whitespace in XFF for IP whitelisting

[olmoser]

What does this PR do?

Trims whitespace from X-Forwarded-For header values.

Motivation

In case there are multiple comma-separated values for the XFF header, there might be trailing whitespace after the comma e.g.

X-Forwarded-For: 1.2.3.4, 1.1.1.1, 8.8.8.8

If that's the case, then net.parseIP will return nil and the whitelist check will fail.

This situation was not caught by the test since the fixture:

{
	desc:                "allow UseXForwardedFor, remoteAddr not in range, UseXForwardedFor in range (compact XFF)",
	whiteList:           []string{"1.2.3.4/24"},
	allowXForwardedFor:  true,
	remoteAddr:          "10.2.3.1:123",
	xForwardedForValues: []string{"1.2.3.1, 10.2.3.1"},
	authorized:          true,
},

listed the matching IP as the first value in the comma separated value, hence not testing the second value (10.2.3.1) which contains the whitespace.

More

• Added/updated tests
• Added/updated documentation

Additional Notes

[juliens]

Good catch 👏

[juliens]

LGTM

[jbdoumenjou]

LGTM

[ldez]

LGTM