76 lines
2.2 KiB
Go
76 lines
2.2 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packet
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import (
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"golang.org/x/crypto/openpgp/errors"
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"io"
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)
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// Reader reads packets from an io.Reader and allows packets to be 'unread' so
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// that they result from the next call to Next.
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type Reader struct {
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q []Packet
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readers []io.Reader
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}
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// New io.Readers are pushed when a compressed or encrypted packet is processed
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// and recursively treated as a new source of packets. However, a carefully
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// crafted packet can trigger an infinite recursive sequence of packets. See
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// http://mumble.net/~campbell/misc/pgp-quine
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// https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2013-4402
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// This constant limits the number of recursive packets that may be pushed.
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const maxReaders = 32
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// Next returns the most recently unread Packet, or reads another packet from
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// the top-most io.Reader. Unknown packet types are skipped.
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func (r *Reader) Next() (p Packet, err error) {
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if len(r.q) > 0 {
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p = r.q[len(r.q)-1]
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r.q = r.q[:len(r.q)-1]
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return
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}
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for len(r.readers) > 0 {
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p, err = Read(r.readers[len(r.readers)-1])
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if err == nil {
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return
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}
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if err == io.EOF {
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r.readers = r.readers[:len(r.readers)-1]
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continue
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}
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if _, ok := err.(errors.UnknownPacketTypeError); !ok {
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return nil, err
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}
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}
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return nil, io.EOF
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}
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// Push causes the Reader to start reading from a new io.Reader. When an EOF
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// error is seen from the new io.Reader, it is popped and the Reader continues
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// to read from the next most recent io.Reader. Push returns a StructuralError
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// if pushing the reader would exceed the maximum recursion level, otherwise it
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// returns nil.
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func (r *Reader) Push(reader io.Reader) (err error) {
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if len(r.readers) >= maxReaders {
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return errors.StructuralError("too many layers of packets")
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}
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r.readers = append(r.readers, reader)
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return nil
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}
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// Unread causes the given Packet to be returned from the next call to Next.
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func (r *Reader) Unread(p Packet) {
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r.q = append(r.q, p)
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}
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func NewReader(r io.Reader) *Reader {
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return &Reader{
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q: nil,
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readers: []io.Reader{r},
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}
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}
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