[release-branch.go1.20] crypto/x509: tolerate multiple matching chain…

…s in testVerify

Due to the semantics of roots, a root store may contain two valid roots
that have the same subject (but different SPKIs) at the asme time. As
such in testVerify it is possible that when we verify a certificate we
may get two chains that has the same stringified representation.

Rather than doing something fancy to include keys (which is just overly
complicated), tolerate multiple matches.

Updates #60925
Fixes #60947

Change-Id: I5f51f7635801762865a536bcb20ec75f217a36ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/505035
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Roland Shoemaker <roland@golang.org>
Auto-Submit: Roland Shoemaker <roland@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 2031366)
Reviewed-on: https://go-review.googlesource.com/c/go/+/505275
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Heschi Kreinick <heschi@google.com>

src/crypto/x509/verify_test.go

@@ -500,22 +500,21 @@ func testVerify(t *testing.T, test verifyTest, useSystemRoots bool) {
 		return true
 	}
 
-	// Every expected chain should match 1 returned chain
+	// Every expected chain should match one (or more) returned chain. We tolerate multiple
+	// matches, as due to root store semantics it is plausible that (at least on the system
+	// verifiers) multiple identical (looking) chains may be returned when two roots with the
+	// same subject are present.
 	for _, expectedChain := range test.expectedChains {
-		nChainMatched := 0
+		var match bool
 		for _, chain := range chains {
 			if doesMatch(expectedChain, chain) {
-				nChainMatched++
+				match = true
+				break
 			}
 		}
 
-		if nChainMatched != 1 {
-			t.Errorf("Got %v matches instead of %v for expected chain %v", nChainMatched, 1, expectedChain)
-			for _, chain := range chains {
-				if doesMatch(expectedChain, chain) {
-					t.Errorf("\t matched %v", chainToDebugString(chain))
-				}
-			}
+		if !match {
+			t.Errorf("No match found for %v", expectedChain)
 		}
 	}