goc_marek/go_S-MIME
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Added parsing of mime messages needed to verify signed messages.

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InfiniteLoopSpace 2018-11-14 15:00:02 +01:00
parent 896ad654c8
commit 6604a9bc8c
2 changed files with 363 additions and 0 deletions
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286
mime/mime.go Normal file
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//Package MIME implemets parsing of MIME and MIME/multipart messages
//needed to verfiy multipart/signed messages
package mime
import (
"bytes"
"errors"
"fmt"
"strings"
"unicode"
gomime "mime"
)
//A MIME message
type MIME struct {
headerFld Lines
interm Line
body Lines
}
//Returns the header of the message
func (m *MIME) Header() []byte {
return m.headerFld.bytes(nil)
}
//Sets the body of the message
func (m *MIME) SetBody(body []byte) {
m.body = ParseLines((body))
}
//Gets the body of the message
func (m *MIME) Body() []byte {
return m.body.bytes(nil)
}
//Gets the full message
func (m *MIME) Full() []byte {
var sep []byte
sep = append(sep, m.interm.Line...)
sep = append(sep, m.interm.endOfLine...)
return append(append(m.Header(), sep...), m.Body()...)
}
//Adds a header field to the header of the message
func (m *MIME) AddHeaderField(key, value []byte) {
var field []byte
field = append(field, key...)
field = append(field, []byte(": ")...)
field = append(field, value...)
newField := Line{field, []byte("\n")}
m.headerFld = append(m.headerFld, newField)
}
//Removes a header fild from the header of the message
func (m *MIME) DeleteHeaderField(key []byte) {
for i := len(m.headerFld) - 1; i >= 0; i-- {
colonInd := bytes.Index(m.headerFld[i].Line, []byte(":"))
k := m.headerFld[i].Line[:colonInd]
if bytes.Equal(bytes.ToLower(k), bytes.ToLower(key)) {
m.headerFld = append(m.headerFld[:i], m.headerFld[i+1:]...)
}
}
}
//Gets the header field with the given key
func (m *MIME) GetHeaderField(key []byte) (values [][]byte) {
for i := range m.headerFld {
colonInd := bytes.Index(m.headerFld[i].Line, []byte(":"))
if colonInd < 1 {
fmt.Printf("%q\n", (m.headerFld[i].Line))
}
k := m.headerFld[i].Line[:colonInd]
if bytes.Equal(bytes.ToLower(k), bytes.ToLower(key)) {
if colonInd+2 < len(m.headerFld[i].Line) {
values = append(values, m.headerFld[i].Line[colonInd+2:])
}
}
}
return
}
//Sets the header field with the given key
func (m *MIME) SetHeaderField(key, value []byte) {
m.DeleteHeaderField(key)
var field []byte
field = append(field, key...)
field = append(field, []byte(": ")...)
field = append(field, value...)
newField := Line{field, []byte("\n")}
m.headerFld = append(m.headerFld, newField)
}
//Parses the mediatype of the message
func (m *MIME) ParseMediaType() (mediatype string, params map[string]string, err error) {
contentType := m.GetHeaderField([]byte("Content-Type"))
if len(contentType) != 1 {
err = errors.New("Multiple or no Content-Type field")
return
}
mediatype, params, err = gomime.ParseMediaType(string(m.GetHeaderField([]byte("Content-Type"))[0]))
return
}
//Get the parts of a multipart Message
func (m *MIME) MultipartGetParts() (parts []Lines, err error) {
mediaType, params, err := m.ParseMediaType()
if !strings.HasPrefix(mediaType, "multipart/") {
err = errors.New("Message is not multipart")
return
}
boundary := params["boundary"]
if boundary == "" {
err = errors.New("Mulitpart message has no boundary")
return
}
var boundaryIndex []int
for i := range m.body {
if strings.HasPrefix(string(m.body[i].Line), "--"+boundary) {
boundaryIndex = append(boundaryIndex, i)
}
if strings.HasPrefix(string(m.body[i].Line), "--"+boundary+"--") {
break
}
}
for i := 0; i < len(boundaryIndex)-1; i++ {
part := make([]Line, boundaryIndex[i+1]-(boundaryIndex[i]+1))
copy(part, m.body[boundaryIndex[i]+1:boundaryIndex[i+1]])
parts = append(parts, part) //m.body[boundaryIndex[i]+1:boundaryIndex[i+1]])
}
for i := range parts {
parts[i][len(parts[i])-1] = Line{parts[i][len(parts[i])-1].Line, nil}
}
return
}
var (
CRLF = []byte("\r\n")
CR = []byte("\r")
LF = []byte("\n")
SPACE = []byte(" ")[0]
HTAB = []byte("\t")[0]
)
//Parses a MIME message
func Parse(raw []byte) (m MIME) {
rawLines := ParseLines(raw)
return parseMIME(rawLines)
}
func parseMIME(rawLines Lines) (m MIME) {
var headerField Line
for i := range rawLines {
if len(rawLines[i].Line) > 0 && isContinuedLine(rawLines[i].Line) && i > 0 && !isEmpty(rawLines[i].Line) {
headerField.Line = append(headerField.Line, headerField.endOfLine...)
headerField.Line = append(headerField.Line, rawLines[i].Line...)
headerField.endOfLine = rawLines[i].endOfLine
} else {
if i > 0 {
m.headerFld = append(m.headerFld, headerField)
}
//Next headerField
headerField = rawLines[i]
}
// Empty line seprates header and body
if isEmpty(rawLines[i].Line) {
m.interm = rawLines[i]
m.body = rawLines[i+1:]
break
}
}
return
}
//Line of a MIME message
type Line struct {
Line []byte
endOfLine []byte
}
//Multiple lines, needed for body and header
type Lines []Line
//Parsing linebreaks
func ParseLines(raw []byte) (lines Lines) {
oneLine := Line{raw, nil}
lines = Lines{oneLine}
lines = lines.splitLine(CRLF)
lines = lines.splitLine(CR)
lines = lines.splitLine(LF)
return
}
func (l Lines) splitLine(sep []byte) (newL Lines) {
newL = Lines{}
for _, line := range l {
split := bytes.Split(line.Line, sep)
if len(split) > 1 {
for i := 0; i < len(split)-1; i++ {
newL = append(newL, Line{split[i], sep})
}
newL = append(newL, Line{split[len(split)-1], nil})
} else {
newL = append(newL, line)
}
}
return
}
//Gives the bytes of the Lines with given linebreak. (e.g. for signed S/MIME use Bytes(mime.CRLF))
func (l Lines) Bytes(sep []byte) (raw []byte) {
return l.bytes(sep)
}
func (l Lines) bytes(sep []byte) (raw []byte) {
for i := range l {
raw = append(raw, l[i].Line...)
if len(l[i].endOfLine) != 0 && sep != nil {
raw = append(raw, sep...)
} else {
raw = append(raw, l[i].endOfLine...)
}
}
return raw
}
//Header field folding https://tools.ietf.org/html/rfc822#section-3.1.1
func isEmpty(s []byte) bool {
return len(bytes.TrimSpace(s)) == 0
}
func isContinuedLine(s []byte) bool {
if !(s[0] != ' ' && s[0] != '\t') {
return true
}
if unicode.IsSpace(bytes.Runes(s[:2])[0]) {
fmt.Println("Continued Line with unicode space found.")
return true
}
return false
}

77
mime/mime_test.go Normal file
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package mime
import (
"bytes"
"strings"
"testing"
)
func TestParsing(t *testing.T) {
mail := Parse([]byte(sampleMsg))
full := mail.Full()
if !bytes.Equal(full, []byte(sampleMsg)) {
t.Error("Parsing mail changes the content!")
}
mediaType, _, err := mail.ParseMediaType()
if err != nil {
t.Error(err)
}
if strings.Compare(mediaType, "multipart/signed") != 0 {
t.Error("Mediatype parsed not corretly!")
}
parts, err := mail.MultipartGetParts()
if err != nil {
t.Error(err)
}
for i := range parts {
if !bytes.Equal(parts[i].Bytes(nil), msgParts[i]) {
t.Fatal("Parts not corretly parsed")
}
}
}
//3.4.3.3. Sample multipart/signed Message https://tools.ietf.org/html/rfc5751#section-3.4
const sampleMsg = `Content-Type: multipart/signed;
protocol="application/pkcs7-signature";
micalg=sha1; boundary=boundary42
--boundary42
Content-Type: text/plain
This is a clear-signed message.
--boundary42
Content-Type: application/pkcs7-signature; name=smime.p7s
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7s
ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4VQpfyF467GhIGfHfYT6
4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756tbB9HGTrfvbnj
n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4
7GhIGfHfYT64VQbnj756
--boundary42--`
var msgParts = [][]byte{[]byte(part1), []byte(part2)}
const part1 = `Content-Type: text/plain
This is a clear-signed message.
`
const part2 = `Content-Type: application/pkcs7-signature; name=smime.p7s
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7s
ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4VQpfyF467GhIGfHfYT6
4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756tbB9HGTrfvbnj
n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4
7GhIGfHfYT64VQbnj756
`