stupidgcm: detect AES-GCM acceleration like crypto/tls

Instead of just looking for AES, also look for PCLMULQDQ,
like crypto/tls does.

Fixes: https://github.com/rfjakob/gocryptfs/issues/822

1 files changed, 28 insertions, 0 deletions

diff --git a/internal/stupidgcm/cipher_suites.go b/internal/stupidgcm/cipher_suites.go
new file mode 100644
index 0000000..fd032fd
--- /dev/null
+++ b/internal/stupidgcm/cipher_suites.go
@@ -0,0 +1,28 @@
+package stupidgcm
+
+import (
+	"runtime"
+
+	"golang.org/x/sys/cpu"
+)
+
+// ********
+// Carbon-copied from Go Stdlib
+// https://github.com/golang/go/blob/45967bb18e04fa6dc62c2786c87ce120443c64f6/src/crypto/tls/cipher_suites.go#L367
+// ********
+
+var (
+	hasGCMAsmAMD64 = cpu.X86.HasAES && cpu.X86.HasPCLMULQDQ
+	hasGCMAsmARM64 = cpu.ARM64.HasAES && cpu.ARM64.HasPMULL
+	// Keep in sync with crypto/aes/cipher_s390x.go.
+	hasGCMAsmS390X = cpu.S390X.HasAES && cpu.S390X.HasAESCBC && cpu.S390X.HasAESCTR &&
+		(cpu.S390X.HasGHASH || cpu.S390X.HasAESGCM)
+
+	hasAESGCMHardwareSupport = runtime.GOARCH == "amd64" && hasGCMAsmAMD64 ||
+		runtime.GOARCH == "arm64" && hasGCMAsmARM64 ||
+		runtime.GOARCH == "s390x" && hasGCMAsmS390X
+)
+
+// ********
+// End carbon-copy
+// ********