crypto,testing/cryptotest: ignore random io.Reader params, add SetGlobalRandom

First, we centralize all random bytes generation through drbg.Read. The
rest of the FIPS 140-3 module can't use external functions anyway, so
drbg.Read needs to have all the logic.

Then, make sure that the crypto/... tree uses drbg.Read (or the new
crypto/internal/rand.Reader wrapper) instead of crypto/rand, so it is
unaffected by applications setting crypto/rand.Reader.

Next, pass all unspecified random io.Reader parameters through the new
crypto/internal/rand.CustomReader, which just redirects to drbg.Read
unless GODEBUG=cryptocustomrand=1 is set. Move all the calls to
MaybeReadByte there, since it's only needed for these custom Readers.

Finally, add testing/cryptotest.SetGlobalRandom which sets
crypto/rand.Reader to a locked deterministic source and overrides
drbg.Read. This way SetGlobalRandom should affect all cryptographic
randomness in the standard library.

Fixes #70942

Co-authored-by: qiulaidongfeng <2645477756@qq.com>
Change-Id: I6a6a69641311d9fac318abcc6d79677f0e406100
Reviewed-on: https://go-review.googlesource.com/c/go/+/724480
Reviewed-by: Nicholas Husin <nsh@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Nicholas Husin <husin@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/testing/testing.go b/src/testing/testing.go
index 0d1d08ca89..34b45b41b9 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -1749,7 +1749,7 @@ func pcToName(pc uintptr) string {
 	return frame.Function
 }
 
-const parallelConflict = `testing: test using t.Setenv or t.Chdir can not use t.Parallel`
+const parallelConflict = `testing: test using t.Setenv, t.Chdir, or cryptotest.SetGlobalRandom can not use t.Parallel`
 
 // Parallel signals that this test is to be run in parallel with (and only with)
 // other parallel tests. When a test is run multiple times due to use of
@@ -1820,6 +1820,13 @@ func (t *T) Parallel() {
 	t.lastRaceErrors.Store(int64(race.Errors()))
 }
 
+// checkParallel is called by [testing/cryptotest.SetGlobalRandom].
+//
+//go:linkname checkParallel testing.checkParallel
+func checkParallel(t *T) {
+	t.checkParallel()
+}
+
 func (t *T) checkParallel() {
 	// Non-parallel subtests that have parallel ancestors may still
 	// run in parallel with other tests: they are only non-parallel