crypto/rand: use arc4random_buf() on OpenBSD

OpenBSD system calls are mediated by libc anyway, and arc4random_buf()
is the preferred mechanism to obtain random bytes.

Also, rename NetBSD's function to reflect it's not actually calling
getentropy(3).

Cq-Include-Trybots: luci.golang.try:gotip-openbsd-amd64
Change-Id: Id1f3f7af16750537e2420bcf44b086de5854198c
Reviewed-on: https://go-review.googlesource.com/c/go/+/608395
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Bypass: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>

22 files changed, 33 insertions, 187 deletions

diff --git a/src/crypto/rand/rand.go b/src/crypto/rand/rand.go
index 0911666f00..b3d0a7368f 100644
--- a/src/crypto/rand/rand.go
+++ b/src/crypto/rand/rand.go
@@ -21,8 +21,7 @@ import (
 //
 //   - On Linux, FreeBSD, Dragonfly, and Solaris, Reader uses getrandom(2).
 //   - On legacy Linux (< 3.17), Reader opens /dev/urandom on first use.
-//   - On macOS and iOS, Reader uses arc4random_buf(3).
-//   - On OpenBSD, Reader uses getentropy(2).
+//   - On macOS, iOS, and OpenBSD Reader, uses arc4random_buf(3).
 //   - On NetBSD, Reader uses the kern.arandom sysctl.
 //   - On Windows, Reader uses the ProcessPrng API.
 //   - On js/wasm, Reader uses the Web Crypto API.
diff --git a/src/crypto/rand/rand_darwin.go b/src/crypto/rand/rand_arc4random.go
index abbfec87cb..f2e27004f8 100644
--- a/src/crypto/rand/rand_darwin.go
+++ b/src/crypto/rand/rand_arc4random.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin || openbsd
+
 package rand
 
 import "internal/syscall/unix"
diff --git a/src/crypto/rand/rand_getentropy.go b/src/crypto/rand/rand_netbsd.go
index b9e41433a2..b25d261e15 100644
--- a/src/crypto/rand/rand_getentropy.go
+++ b/src/crypto/rand/rand_netbsd.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build openbsd || netbsd
-
 package rand
 
 import "internal/syscall/unix"
@@ -11,11 +9,13 @@ import "internal/syscall/unix"
 func read(b []byte) error {
 	for len(b) > 0 {
 		size := len(b)
+		// "Returns independent uniformly distributed bytes at random each time,
+		// as many as requested up to 256, derived from the system entropy pool;
+		// see rnd(4)." -- man sysctl(7)
 		if size > 256 {
 			size = 256
 		}
-		// getentropy(2) returns a maximum of 256 bytes per call.
-		if err := unix.GetEntropy(b[:size]); err != nil {
+		if err := unix.Arandom(b[:size]); err != nil {
 			return err
 		}
 		b = b[size:]
diff --git a/src/internal/syscall/unix/getentropy_netbsd.go b/src/internal/syscall/unix/arandom_netbsd.go
index 02bac1be00..23ca8739e8 100644
--- a/src/internal/syscall/unix/getentropy_netbsd.go
+++ b/src/internal/syscall/unix/arandom_netbsd.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build netbsd
-
 package unix
 
 import (
@@ -17,7 +15,7 @@ const (
 	_KERN_ARND = 81
 )
 
-func GetEntropy(p []byte) error {
+func Arandom(p []byte) error {
 	mib := [2]uint32{_CTL_KERN, _KERN_ARND}
 	n := uintptr(len(p))
 	_, _, errno := syscall.Syscall6(
diff --git a/src/internal/syscall/unix/arc4random_openbsd.go b/src/internal/syscall/unix/arc4random_openbsd.go
new file mode 100644
index 0000000000..652e0cb19d
--- /dev/null
+++ b/src/internal/syscall/unix/arc4random_openbsd.go
@@ -0,0 +1,23 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package unix
+
+import (
+	"internal/abi"
+	"syscall"
+	"unsafe"
+)
+
+//go:linkname syscall_syscall syscall.syscall
+func syscall_syscall(fn, a1, a2, a3 uintptr) (r1, r2 uintptr, err syscall.Errno)
+
+//go:cgo_import_dynamic libc_arc4random_buf arc4random_buf "libc.so"
+
+func libc_arc4random_buf_trampoline()
+
+func ARC4Random(p []byte) {
+	syscall_syscall(abi.FuncPCABI0(libc_arc4random_buf_trampoline),
+		uintptr(unsafe.Pointer(unsafe.SliceData(p))), uintptr(len(p)), 0)
+}
diff --git a/src/internal/syscall/unix/asm_openbsd.s b/src/internal/syscall/unix/asm_openbsd.s
index cc54a14ca5..d6c4320539 100644
--- a/src/internal/syscall/unix/asm_openbsd.s
+++ b/src/internal/syscall/unix/asm_openbsd.s
@@ -8,3 +8,5 @@
 
 TEXT ·libc_faccessat_trampoline(SB),NOSPLIT,$0-0
         JMP	libc_faccessat(SB)
+TEXT ·libc_arc4random_buf_trampoline(SB),NOSPLIT,$0-0
+        JMP	libc_arc4random_buf(SB)
diff --git a/src/internal/syscall/unix/getentropy_openbsd.go b/src/internal/syscall/unix/getentropy_openbsd.go
deleted file mode 100644
index 7516ac7ce7..0000000000
--- a/src/internal/syscall/unix/getentropy_openbsd.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build openbsd && !mips64
-
-package unix
-
-import _ "unsafe" // for linkname
-
-// GetEntropy calls the OpenBSD getentropy system call.
-func GetEntropy(p []byte) error {
-	return getentropy(p)
-}
-
-//go:linkname getentropy syscall.getentropy
-//go:noescape
-func getentropy(p []byte) error
diff --git a/src/internal/syscall/unix/getentropy_openbsd_mips64.go b/src/internal/syscall/unix/getentropy_openbsd_mips64.go
deleted file mode 100644
index d5caa8095a..0000000000
--- a/src/internal/syscall/unix/getentropy_openbsd_mips64.go
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package unix
-
-import (
-	"syscall"
-	"unsafe"
-)
-
-// getentropy(2)'s syscall number, from /usr/src/sys/kern/syscalls.master
-const entropyTrap uintptr = 7
-
-// GetEntropy calls the OpenBSD getentropy system call.
-func GetEntropy(p []byte) error {
-	_, _, errno := syscall.Syscall(entropyTrap,
-		uintptr(unsafe.Pointer(&p[0])),
-		uintptr(len(p)),
-		0)
-	if errno != 0 {
-		return errno
-	}
-	return nil
-}
diff --git a/src/syscall/linkname_openbsd.go b/src/syscall/linkname_openbsd.go
index 5f5c517ab5..bbb56c10ec 100644
--- a/src/syscall/linkname_openbsd.go
+++ b/src/syscall/linkname_openbsd.go
@@ -12,4 +12,3 @@ import _ "unsafe"
 //go:linkname unlinkat
 //go:linkname openat
 //go:linkname fstatat
-//go:linkname getentropy
diff --git a/src/syscall/syscall_openbsd_libc.go b/src/syscall/syscall_openbsd_libc.go
index 5dea268c3e..13311398b9 100644
--- a/src/syscall/syscall_openbsd_libc.go
+++ b/src/syscall/syscall_openbsd_libc.go
@@ -79,7 +79,6 @@ func syscall9X(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr,
 //sysnb execve(path *byte, argv **byte, envp **byte) (err error)
 //sysnb exit(res int) (err error)
 //sys   ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
-//sysnb getentropy(p []byte) (err error)
 //sys   fstatat(fd int, path string, stat *Stat_t, flags int) (err error)
 //sys   unlinkat(fd int, path string, flags int) (err error)
 //sys   openat(fd int, path string, flags int, perm uint32) (fdret int, err error)
diff --git a/src/syscall/zsyscall_openbsd_386.go b/src/syscall/zsyscall_openbsd_386.go
index d2bd3ea012..c8cf7f231b 100644
--- a/src/syscall/zsyscall_openbsd_386.go
+++ b/src/syscall/zsyscall_openbsd_386.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_386.s b/src/syscall/zsyscall_openbsd_386.s
index 9a820e9f3e..f86ac2c077 100644
--- a/src/syscall/zsyscall_openbsd_386.s
+++ b/src/syscall/zsyscall_openbsd_386.s
@@ -227,8 +227,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_exit(SB)
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_ptrace(SB)
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	JMP	libc_getentropy(SB)
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_fstatat(SB)
 TEXT ·libc_unlinkat_trampoline(SB),NOSPLIT,$0-0
diff --git a/src/syscall/zsyscall_openbsd_amd64.go b/src/syscall/zsyscall_openbsd_amd64.go
index 170a74b457..9188756a87 100644
--- a/src/syscall/zsyscall_openbsd_amd64.go
+++ b/src/syscall/zsyscall_openbsd_amd64.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_amd64.s b/src/syscall/zsyscall_openbsd_amd64.s
index 9b70dc096e..4ec6220281 100644
--- a/src/syscall/zsyscall_openbsd_amd64.s
+++ b/src/syscall/zsyscall_openbsd_amd64.s
@@ -227,8 +227,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_exit(SB)
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_ptrace(SB)
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	JMP	libc_getentropy(SB)
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_fstatat(SB)
 TEXT ·libc_unlinkat_trampoline(SB),NOSPLIT,$0-0
diff --git a/src/syscall/zsyscall_openbsd_arm.go b/src/syscall/zsyscall_openbsd_arm.go
index e75bd0b443..ecdfa63672 100644
--- a/src/syscall/zsyscall_openbsd_arm.go
+++ b/src/syscall/zsyscall_openbsd_arm.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_arm.s b/src/syscall/zsyscall_openbsd_arm.s
index 0333377b8b..75251d0305 100644
--- a/src/syscall/zsyscall_openbsd_arm.s
+++ b/src/syscall/zsyscall_openbsd_arm.s
@@ -227,8 +227,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_exit(SB)
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_ptrace(SB)
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	JMP	libc_getentropy(SB)
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_fstatat(SB)
 TEXT ·libc_unlinkat_trampoline(SB),NOSPLIT,$0-0
diff --git a/src/syscall/zsyscall_openbsd_arm64.go b/src/syscall/zsyscall_openbsd_arm64.go
index bc027b4475..d28d3c5e1e 100644
--- a/src/syscall/zsyscall_openbsd_arm64.go
+++ b/src/syscall/zsyscall_openbsd_arm64.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_arm64.s b/src/syscall/zsyscall_openbsd_arm64.s
index 654e6c69a3..deea88ec7c 100644
--- a/src/syscall/zsyscall_openbsd_arm64.s
+++ b/src/syscall/zsyscall_openbsd_arm64.s
@@ -227,8 +227,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_exit(SB)
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_ptrace(SB)
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	JMP	libc_getentropy(SB)
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_fstatat(SB)
 TEXT ·libc_unlinkat_trampoline(SB),NOSPLIT,$0-0
diff --git a/src/syscall/zsyscall_openbsd_ppc64.go b/src/syscall/zsyscall_openbsd_ppc64.go
index 6808092a5a..0e6828bcaf 100644
--- a/src/syscall/zsyscall_openbsd_ppc64.go
+++ b/src/syscall/zsyscall_openbsd_ppc64.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_ppc64.s b/src/syscall/zsyscall_openbsd_ppc64.s
index 86a5745c0a..cc4eb952eb 100644
--- a/src/syscall/zsyscall_openbsd_ppc64.s
+++ b/src/syscall/zsyscall_openbsd_ppc64.s
@@ -340,9 +340,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	CALL	libc_ptrace(SB)
 	RET
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	CALL	libc_getentropy(SB)
-	RET
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	CALL	libc_fstatat(SB)
 	RET
diff --git a/src/syscall/zsyscall_openbsd_riscv64.go b/src/syscall/zsyscall_openbsd_riscv64.go
index 2979ff78c2..920147074d 100644
--- a/src/syscall/zsyscall_openbsd_riscv64.go
+++ b/src/syscall/zsyscall_openbsd_riscv64.go
@@ -1854,26 +1854,6 @@ func libc_ptrace_trampoline()
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getentropy(p []byte) (err error) {
-	var _p0 unsafe.Pointer
-	if len(p) > 0 {
-		_p0 = unsafe.Pointer(&p[0])
-	} else {
-		_p0 = unsafe.Pointer(&_zero)
-	}
-	_, _, e1 := rawSyscall(abi.FuncPCABI0(libc_getentropy_trampoline), uintptr(_p0), uintptr(len(p)), 0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-func libc_getentropy_trampoline()
-
-//go:cgo_import_dynamic libc_getentropy getentropy "libc.so"
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)
diff --git a/src/syscall/zsyscall_openbsd_riscv64.s b/src/syscall/zsyscall_openbsd_riscv64.s
index c8728190e5..14b7b23222 100644
--- a/src/syscall/zsyscall_openbsd_riscv64.s
+++ b/src/syscall/zsyscall_openbsd_riscv64.s
@@ -227,8 +227,6 @@ TEXT ·libc_exit_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_exit(SB)
 TEXT ·libc_ptrace_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_ptrace(SB)
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0
-	JMP	libc_getentropy(SB)
 TEXT ·libc_fstatat_trampoline(SB),NOSPLIT,$0-0
 	JMP	libc_fstatat(SB)
 TEXT ·libc_unlinkat_trampoline(SB),NOSPLIT,$0-0