mirror of
https://github.com/netbirdio/gvisor.git
synced 2026-05-22 17:12:49 -07:00
Ayush Ranjan
e0bdd0d576
This undocumented behavior manifests in Linux and some apps depend on it. See drivers/char/random.c:get_random_bytes_user(). Fixes #9445 Fixes #4988 PiperOrigin-RevId: 570833447
67 lines
2.0 KiB
Go
67 lines
2.0 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package linux
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import (
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"math"
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"gvisor.dev/gvisor/pkg/errors/linuxerr"
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"gvisor.dev/gvisor/pkg/hostarch"
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"gvisor.dev/gvisor/pkg/rand"
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"gvisor.dev/gvisor/pkg/safemem"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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const (
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_GRND_NONBLOCK = 0x1
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_GRND_RANDOM = 0x2
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)
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// GetRandom implements the linux syscall getrandom(2).
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//
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// In a multi-tenant/shared environment, the only valid implementation is to
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// fetch data from the urandom pool, otherwise starvation attacks become
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// possible. The urandom pool is also expected to have plenty of entropy, thus
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// the GRND_RANDOM flag is ignored. The GRND_NONBLOCK flag does not apply, as
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// the pool will already be initialized.
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func GetRandom(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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addr := args[0].Pointer()
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length := args[1].SizeT()
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flags := args[2].Int()
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// Flags are checked for validity but otherwise ignored. See above.
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if flags & ^(_GRND_NONBLOCK|_GRND_RANDOM) != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if length > math.MaxInt32 {
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length = math.MaxInt32
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}
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ar, ok := addr.ToRange(uint64(length))
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if !ok {
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return 0, nil, linuxerr.EFAULT
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}
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n, err := t.MemoryManager().CopyOutFrom(t, hostarch.AddrRangeSeqOf(ar), safemem.FromIOReader{rand.Reader}, usermem.IOOpts{
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AddressSpaceActive: true,
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})
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if n > 0 {
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return uintptr(n), nil, nil
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}
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return 0, nil, err
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}
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