150 lines
3.2 KiB
Go
150 lines
3.2 KiB
Go
// Copyright (c) 2024 Proton AG
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//
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// This file is part of Proton Mail Bridge.
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//
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// Proton Mail Bridge is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Proton Mail Bridge is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
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package message
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import (
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"bufio"
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"bytes"
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"io"
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"unicode"
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"github.com/emersion/go-message/textproto"
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"github.com/pkg/errors"
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)
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// HeaderLines returns each line in the given header.
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func HeaderLines(header []byte) [][]byte {
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var (
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lines [][]byte
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quote int
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)
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forEachLine(bufio.NewReader(bytes.NewReader(header)), func(line []byte) {
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l := bytes.SplitN(line, []byte(`: `), 2)
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isLineContinuation := quote%2 != 0 || // no quotes opened
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!bytes.Equal(bytes.TrimLeftFunc(l[0], unicode.IsSpace), l[0]) // has whitespace indent at beginning
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switch {
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case len(bytes.TrimSpace(line)) == 0:
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lines = append(lines, line)
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case isLineContinuation:
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if len(lines) > 0 {
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lines[len(lines)-1] = append(lines[len(lines)-1], line...)
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} else {
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lines = append(lines, line)
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}
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default:
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lines = append(lines, line)
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}
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quote += bytes.Count(line, []byte(`"`))
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})
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return lines
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}
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func forEachLine(br *bufio.Reader, fn func([]byte)) {
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for {
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b, err := br.ReadBytes('\n')
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if err != nil {
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if !errors.Is(err, io.EOF) {
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panic(err)
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}
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if len(b) > 0 {
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fn(b)
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}
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return
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}
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fn(b)
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}
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}
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func readHeaderBody(b []byte) (*textproto.Header, []byte, error) {
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rawHeader, body, err := splitHeaderBody(b)
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if err != nil {
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return nil, nil, err
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}
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lines := HeaderLines(rawHeader)
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var header textproto.Header
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// We assume that everything before first occurrence of empty line is header.
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// If header is invalid for any reason or empty - put everything as body and let header be empty.
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if !isHeaderValid(lines) {
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return &header, b, nil
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}
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// We add lines in reverse so that calling textproto.WriteHeader later writes with the correct order.
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for i := len(lines) - 1; i >= 0; i-- {
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if len(bytes.TrimSpace(lines[i])) > 0 {
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header.AddRaw(lines[i])
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}
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}
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return &header, body, nil
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}
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func isHeaderValid(headerLines [][]byte) bool {
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if len(headerLines) == 0 {
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return false
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}
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for _, line := range headerLines {
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if (bytes.IndexByte(line, ':') == -1) && (len(bytes.TrimSpace(line)) > 0) {
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return false
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}
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}
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return true
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}
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func splitHeaderBody(b []byte) ([]byte, []byte, error) {
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br := bufio.NewReader(bytes.NewReader(b))
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var header []byte
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for {
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b, err := br.ReadBytes('\n')
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if err != nil {
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if !errors.Is(err, io.EOF) {
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panic(err)
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}
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break
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}
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header = append(header, b...)
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if len(bytes.TrimSpace(b)) == 0 {
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break
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}
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}
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body, err := io.ReadAll(br)
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if err != nil && !errors.Is(err, io.EOF) {
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return nil, nil, err
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}
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return header, body, nil
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}
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