runtime: clean up & go-ify the hash function seeder

Change-Id: I0e95f8a5962c547da20e19a356ae1cf8375c9107
Reviewed-on: https://go-review.googlesource.com/1270Reviewed-by: Russ Cox <rsc@golang.org>

src/runtime/alg.go

@@ -332,18 +332,6 @@ func init() {
 		algarray[alg_MEM128].hash = aeshash
 		algarray[alg_STRING].hash = aeshashstr
 		// Initialize with random data so hash collisions will be hard to engineer.
-		var rnd unsafe.Pointer
-		var n int32
-		get_random_data(&rnd, &n)
-		if n > hashRandomBytes {
-			n = hashRandomBytes
-		}
-		memmove(unsafe.Pointer(&aeskeysched[0]), rnd, uintptr(n))
-		if n < hashRandomBytes {
-			// Not very random, but better than nothing.
-			for t := nanotime(); n < hashRandomBytes; n++ {
-				aeskeysched[n] = byte(t >> uint(8*(n%8)))
-			}
-		}
+		getRandomData(aeskeysched[:])
 	}
 }

src/runtime/os1_darwin.go

@@ -45,20 +45,14 @@ func osinit() {
 	}
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/random\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_dragonfly.go

@@ -97,20 +97,14 @@ func osinit() {
 	ncpu = getncpu()
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/urandom\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_freebsd.go

@@ -96,20 +96,14 @@ func osinit() {
 	ncpu = getncpu()
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/random\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_linux.go

@@ -145,30 +145,18 @@ func osinit() {
 	ncpu = getproccount()
 }
 
-// Random bytes initialized at startup.  These come
-// from the ELF AT_RANDOM auxiliary vector (vdso_linux_amd64.c).
-// byte*	runtime·startup_random_data;
-// uint32	runtime·startup_random_data_len;
-
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/random\x00")
 
-//go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
-	if startup_random_data != nil {
-		*rnd = unsafe.Pointer(startup_random_data)
-		*rnd_len = int32(startup_random_data_len)
+func getRandomData(r []byte) {
+	if startupRandomData != nil {
+		n := copy(r, startupRandomData)
+		extendRandom(r, n)
 		return
 	}
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_netbsd.go

@@ -170,20 +170,14 @@ func osinit() {
 	ncpu = getncpu()
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/urandom\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_openbsd.go

@@ -138,20 +138,14 @@ func osinit() {
 	ncpu = getncpu()
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/urandom\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_plan9.go

@@ -85,20 +85,14 @@ func crash() {
 	*(*int)(nil) = 0
 }
 
-var random_data [_HashRandomBytes]byte
 var random_dev = []byte("/dev/random\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&random_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&random_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&random_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os1_windows.go

@@ -148,24 +148,21 @@ func osinit() {
 	}
 }
 
-var random_data [_HashRandomBytes]byte
-
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	const (
 		prov_rsa_full       = 1
 		crypt_verifycontext = 0xF0000000
 	)
 	var handle uintptr
-	*rnd = nil
-	*rnd_len = 0
+	n := 0
 	if stdcall5(_CryptAcquireContextW, uintptr(unsafe.Pointer(&handle)), 0, 0, prov_rsa_full, crypt_verifycontext) != 0 {
-		if stdcall3(_CryptGenRandom, handle, _HashRandomBytes, uintptr(unsafe.Pointer(&random_data[0]))) != 0 {
-			*rnd = unsafe.Pointer(&random_data[0])
-			*rnd_len = _HashRandomBytes
+		if stdcall3(_CryptGenRandom, handle, uintptr(len(r)), uintptr(unsafe.Pointer(&r[0]))) != 0 {
+			n = len(r)
 		}
 		stdcall2(_CryptReleaseContext, handle, 0)
 	}
+	extendRandom(r, n)
 }
 
 func goenvs() {

src/runtime/os3_solaris.go

@@ -165,20 +165,14 @@ func newosproc(mp *m, _ unsafe.Pointer) {
 	}
 }
 
-var urandom_data [_HashRandomBytes]byte
 var urandom_dev = []byte("/dev/random\x00")
 
 //go:nosplit
-func get_random_data(rnd *unsafe.Pointer, rnd_len *int32) {
+func getRandomData(r []byte) {
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
-	if read(fd, unsafe.Pointer(&urandom_data), _HashRandomBytes) == _HashRandomBytes {
-		*rnd = unsafe.Pointer(&urandom_data[0])
-		*rnd_len = _HashRandomBytes
-	} else {
-		*rnd = nil
-		*rnd_len = 0
-	}
+	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	close(fd)
+	extendRandom(r, int(n))
 }
 
 func goenvs() {

src/runtime/os_linux_386.go

@@ -29,8 +29,7 @@ func sysargs(argc int32, argv **byte) {
 			_vdso = auxv[i+1]
 
 		case _AT_RANDOM:
-			startup_random_data = (*byte)(unsafe.Pointer(uintptr(auxv[i+1])))
-			startup_random_data_len = 16
+			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(auxv[i+1])))[:]
 		}
 	}
 }

src/runtime/runtime2.go

@@ -475,16 +475,33 @@ const (
 	_Structrnd = regSize
 )
 
-var startup_random_data *byte
-var startup_random_data_len uint32
+// startup_random_data holds random bytes initialized at startup.  These come from
+// the ELF AT_RANDOM auxiliary vector (vdso_linux_amd64.go or os_linux_386.go).
+var startupRandomData []byte
+
+// extendRandom extends the random numbers in r[:n] to the whole slice r.
+// Treats n<0 as n==0.
+func extendRandom(r []byte, n int) {
+	if n < 0 {
+		n = 0
+	}
+	for n < len(r) {
+		// Extend random bits using hash function & time seed
+		w := n
+		if w > 16 {
+			w = 16
+		}
+		h := memhash(unsafe.Pointer(&r[n-w]), uintptr(w), uintptr(nanotime()))
+		for i := 0; i < ptrSize && n < len(r); i++ {
+			r[n] = byte(h)
+			n++
+			h >>= 8
+		}
+	}
+}
 
 var invalidptr int32
 
-const (
-	// hashinit wants this many random bytes
-	_HashRandomBytes = 32
-)
-
 /*
  * deferred subroutine calls
  */

src/runtime/vdso_linux_amd64.go

@@ -321,8 +321,7 @@ func sysargs(argc int32, argv **byte) {
 			vdso_parse_symbols(info1, vdso_find_version(info1, &linux26))
 
 		case _AT_RANDOM:
-			startup_random_data = (*byte)(unsafe.Pointer(uintptr(av.a_val)))
-			startup_random_data_len = 16
+			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(av.a_val)))[:]
 		}
 	}
 }