Check that SAML assertions are not expired

[asprouse5]

Add two checks when using artifact binding to verify the SAML assertions are not expired

[coveralls]

Pull Request Test Coverage Report for Build 64

• 6 of 8 (75.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 70.775%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
idp/artifact.go	6	8	75.0%
<!--	Total:	6	8	75.0%	-->

Totals
Change from base Build 60:	0.02%
Covered Lines:	1160
Relevant Lines:	1639

---

💛 - Coveralls

[amdonov]

I'd have to revisit the specs. Are those conditions required? Looks like this code would blow up if those objects are nil.

[asprouse5]

I found this document that outlines a spec for Internet X.509 Public Key Infrastructure Certificates: https://tools.ietf.org/html/rfc5280#section-4.1.2.5. There's nothing concrete, but it seems to be that these values must be present.

This article splits properties into sections, the latter being optional, implying that the top section is not optional: https://knowledge.digicert.com/solution/SO4583.html

Furthermore, I believe a time.Time variable (the type for NotBefore and NotOnOrAfter) cannot be nil. Example:

package main

import (
    "fmt"
    "time"
)

func main() {
    var t time.Time
    fmt.Println(t)
    fmt.Println(t.IsZero())
}

// prints:
// 0001-01-01 00:00:00 +0000 UTC
// true

I am open to making any changes as necessary.