crypto/rand: add randcrash=0 GODEBUG

For #66821

Change-Id: I525c308d6d6243a2bc805e819dcf40b67e52ade5
Reviewed-on: https://go-review.googlesource.com/c/go/+/608435
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>

diff --git a/doc/godebug.md b/doc/godebug.md
index 7b5fd3e48b87d7c59050c462cd5ba12aae2e8a65..a97d8234fe87d24d72f8dabe3b0218b10153be30 100644 (file)
--- a/doc/godebug.md
+++ b/doc/godebug.md
@@ -168,6 +168,11 @@ For Go 1.24, it now defaults to multipathtcp="2", thus
 enabled by default on listerners. Using multipathtcp="0" reverts to the
 pre-Go 1.24 behavior.
 
+Go 1.24 changed [`crypto/rand.Read`](/pkg/crypto/rand/#Read) to crash the
+program on any error. This setting is controlled by the `randcrash` setting.
+For Go 1.24 it defaults to `randcrash=1`.
+Using `randcrash=0` reverts to the pre-Go 1.24 behavior.
+
 ### Go 1.23
 
 Go 1.23 changed the channels created by package time to be unbuffered

diff --git a/src/crypto/rand/rand.go b/src/crypto/rand/rand.go
index b3d0a7368f7fa0550f108055d35b2514a3df4077..7c18d595c2eeaa90e90b7fc2959f0c967e3aaab1 100644 (file)
--- a/src/crypto/rand/rand.go
+++ b/src/crypto/rand/rand.go
@@ -8,6 +8,7 @@ package rand
 
 import (
        "crypto/internal/boring"
+       "internal/godebug"
        "io"
        "os"
        "sync"
@@ -64,6 +65,8 @@ func (r *reader) Read(b []byte) (n int, err error) {
 //go:linkname fatal
 func fatal(string)
 
+var randcrash = godebug.New("randcrash")
+
 // Read fills b with cryptographically secure random bytes. It never returns an
 // error, and always fills b entirely.
 //
@@ -83,6 +86,10 @@ func Read(b []byte) (n int, err error) {
                copy(b, bb)
        }
        if err != nil {
+               if randcrash.Value() == "0" {
+                       randcrash.IncNonDefault()
+                       return 0, err
+               }
                fatal("crypto/rand: failed to read random data (see https://go.dev/issue/66821): " + err.Error())
                panic("unreachable") // To be sure.
        }

diff --git a/src/crypto/rand/rand_linux_test.go b/src/crypto/rand/rand_linux_test.go
index 7516008208020541e5c05c8eadaab4eea013b87b..5238b458e53bb4cb56dc3462b3affd08e0350ef5 100644 (file)
--- a/src/crypto/rand/rand_linux_test.go
+++ b/src/crypto/rand/rand_linux_test.go
@@ -48,20 +48,18 @@ func TestNoGetrandom(t *testing.T) {
                        return
                }
 
-               buf := &bytes.Buffer{}
                cmd := testenv.Command(t, os.Args[0], "-test.v")
-               cmd.Stdout = buf
-               cmd.Stderr = buf
                cmd.Env = append(os.Environ(), "GO_GETRANDOM_DISABLED=1")
-               if err := cmd.Run(); err != nil {
-                       t.Errorf("subprocess failed: %v\n%s", err, buf.Bytes())
+               out, err := cmd.CombinedOutput()
+               if err != nil {
+                       t.Errorf("subprocess failed: %v\n%s", err, out)
                        return
                }
 
-               if !bytes.Contains(buf.Bytes(), []byte("GetRandom returned ENOSYS")) {
+               if !bytes.Contains(out, []byte("GetRandom returned ENOSYS")) {
                        t.Errorf("subprocess did not disable getrandom")
                }
-               if !bytes.Contains(buf.Bytes(), []byte("TestRead")) {
+               if !bytes.Contains(out, []byte("TestRead")) {
                        t.Errorf("subprocess did not run TestRead")
                }
        }()

diff --git a/src/crypto/rand/rand_test.go b/src/crypto/rand/rand_test.go
index f201cf0ff31fc2cade46196269e86a970c12cc2c..0743a2dd043ad1dfb20a5672c32ae586929869d3 100644 (file)
--- a/src/crypto/rand/rand_test.go
+++ b/src/crypto/rand/rand_test.go
@@ -8,7 +8,9 @@ import (
        "bytes"
        "compress/flate"
        "crypto/internal/boring"
+       "errors"
        "internal/race"
+       "internal/testenv"
        "io"
        "os"
        "runtime"
@@ -189,6 +191,44 @@ func TestNoUrandomFallback(t *testing.T) {
        }
 }
 
+func TestReadError(t *testing.T) {
+       if testing.Short() {
+               t.Skip("skipping test in short mode")
+       }
+       testenv.MustHaveExec(t)
+
+       // We run this test in a subprocess because it's expected to crash the
+       // program unless the GODEBUG is set.
+       if os.Getenv("GO_TEST_READ_ERROR") == "1" {
+               defer func(r io.Reader) { Reader = r }(Reader)
+               Reader = readerFunc(func([]byte) (int, error) {
+                       return 0, errors.New("error")
+               })
+               if _, err := Read(make([]byte, 32)); err == nil {
+                       t.Error("Read did not return error")
+               }
+               return
+       }
+
+       cmd := testenv.Command(t, os.Args[0], "-test.run=TestReadError")
+       cmd.Env = append(os.Environ(), "GO_TEST_READ_ERROR=1")
+       out, err := cmd.CombinedOutput()
+       if err == nil {
+               t.Error("subprocess succeeded unexpectedly")
+       }
+       exp := "fatal error: crypto/rand: failed to read random data"
+       if !bytes.Contains(out, []byte(exp)) {
+               t.Errorf("subprocess output does not contain %q: %s", exp, out)
+       }
+
+       cmd = testenv.Command(t, os.Args[0], "-test.run=TestReadError")
+       cmd.Env = append(os.Environ(), "GO_TEST_READ_ERROR=1", "GODEBUG=randcrash=0")
+       out, err = cmd.CombinedOutput()
+       if err != nil {
+               t.Errorf("subprocess failed: %v\n%s", err, out)
+       }
+}
+
 func BenchmarkRead(b *testing.B) {
        b.Run("4", func(b *testing.B) {
                benchmarkRead(b, 4)

diff --git a/src/internal/godebugs/table.go b/src/internal/godebugs/table.go
index 59d4fa7d5b87414a77ca0ef68813d4d6deef0df5..3af86d070a4c0fd2daa1982563e7a0f01ca23ff1 100644 (file)
--- a/src/internal/godebugs/table.go
+++ b/src/internal/godebugs/table.go
@@ -47,6 +47,7 @@ var All = []Info{
        {Name: "netedns0", Package: "net", Changed: 19, Old: "0"},
        {Name: "panicnil", Package: "runtime", Changed: 21, Old: "1"},
        {Name: "randautoseed", Package: "math/rand"},
+       {Name: "randcrash", Package: "crypto/rand", Changed: 24, Old: "0"},
        {Name: "randseednop", Package: "math/rand", Changed: 24, Old: "0"},
        {Name: "tarinsecurepath", Package: "archive/tar"},
        {Name: "tls10server", Package: "crypto/tls", Changed: 22, Old: "1"},

diff --git a/src/runtime/metrics/doc.go b/src/runtime/metrics/doc.go
index 906abb4102e674e73a95f81f2980ab58ab6cffa9..3d2cc6159f2686135eed0f7bafdffbd8e444b5ce 100644 (file)
--- a/src/runtime/metrics/doc.go
+++ b/src/runtime/metrics/doc.go
@@ -306,6 +306,10 @@ Below is the full list of supported metrics, ordered lexicographically.
                The number of non-default behaviors executed by the math/rand
                package due to a non-default GODEBUG=randautoseed=... setting.
 
+       /godebug/non-default-behavior/randcrash:events
+               The number of non-default behaviors executed by the crypto/rand
+               package due to a non-default GODEBUG=randcrash=... setting.
+
        /godebug/non-default-behavior/randseednop:events
                The number of non-default behaviors executed by the math/rand
                package due to a non-default GODEBUG=randseednop=... setting.