1package message

2

3import (

4 "fmt"

5 "strings"

6

7 "github.com/mjl-/mox/dns"

8)

9

10// ../rfc/8601:577

11

12// Authentication-Results header, see RFC 8601.

13type AuthResults struct {

14 Hostname string

15 // Optional version of Authentication-Results header, assumed "1" when absent,

16 // which is common.

17 Version string

18 Comment string // If not empty, header comment without "()", added after Hostname.

19 Methods []AuthMethod // Can be empty, in case of "none".

20}

21

22// ../rfc/8601:598

23

24// AuthMethod is a result for one authentication method.

25//

26// Example encoding in the header: "spf=pass smtp.mailfrom=example.net".

27type AuthMethod struct {

28 // E.g. "dkim", "spf", "iprev", "auth".

29 Method string

30 Version string // For optional method version. "1" is implied when missing, which is common.

31 Result string // Each method has a set of known values, e.g. "pass", "temperror", etc.

32 Comment string // Optional, message header comment.

33 Reason string // Optional.

34 Props []AuthProp

35}

36

37// ../rfc/8601:606

38

39// AuthProp describes properties for an authentication method.

40// Each method has a set of known properties.

41// Encoded in the header as "type.property=value", e.g. "smtp.mailfrom=example.net"

42// for spf.

43type AuthProp struct {

44 // Valid values maintained at https://www.iana.org/assignments/email-auth/email-auth.xhtml

45 Type string

46 Property string

47 Value string

48 // Whether value is address-like (localpart@domain, or domain). Or another value,

49 // which is subject to escaping.

50 IsAddrLike bool

51 Comment string // If not empty, header comment without "()", added after Value.

52}

53

54// MakeAuthProp is a convenient way to make an AuthProp.

55func MakeAuthProp(typ, property, value string, isAddrLike bool, Comment string) AuthProp {

56 return AuthProp{typ, property, value, isAddrLike, Comment}

57}

58

59// todo future: we could store fields as dns.Domain, and when we encode as non-ascii also add the ascii version as a comment.

60

61// Header returns an Authentication-Results header, possibly spanning multiple

62// lines, always ending in crlf.

63func (h AuthResults) Header() string {

64 // Escaping of values: ../rfc/8601:684 ../rfc/2045:661

65

66 optComment := func(s string) string {

67 if s != "" {

68 return " (" + s + ")"

69 }

70 return s

71 }

72

73 w := &HeaderWriter{}

74 w.Add("", "Authentication-Results:"+optComment(h.Comment)+" "+value(h.Hostname, false)+";")

75 for i, m := range h.Methods {

76 w.Newline()

77

78 tokens := []string{}

79 addf := func(format string, args ...any) {

80 s := fmt.Sprintf(format, args...)

81 tokens = append(tokens, s)

82 }

83 addf("%s=%s", m.Method, m.Result)

84 if m.Comment != "" && (m.Reason != "" || len(m.Props) > 0) {

85 addf("(%s)", m.Comment)

86 }

87 if m.Reason != "" {

88 addf("reason=%s", value(m.Reason, false))

89 }

90 for _, p := range m.Props {

91 v := value(p.Value, p.IsAddrLike)

92 addf("%s.%s=%s%s", p.Type, p.Property, v, optComment(p.Comment))

93 }

94 for j, t := range tokens {

95 var sep string

96 if j > 0 {

97 sep = " "

98 }

99 if j == len(tokens)-1 && i < len(h.Methods)-1 {

100 t += ";"

101 }

102 w.Add(sep, t)

103 }

104 }

105 return w.String()

106}

107

108func value(s string, isAddrLike bool) string {

109 quote := s == ""

110 for _, c := range s {

111 // utf-8 does not have to be quoted. ../rfc/6532:242

112 // Characters outside of tokens do. ../rfc/2045:661

113 if c <= ' ' || c == 0x7f || (c == '@' && !isAddrLike) || strings.ContainsRune(`()<>,;:\\"/[]?= `, c) {

114 quote = true

115 break

116 }

117 }

118 if !quote {

119 return s

120 }

121 r := `"`

122 for _, c := range s {

123 if c == '"' || c == '\\' {

124 r += "\\"

125 }

126 r += string(c)

127 }

128 r += `"`

129 return r

130}

131

132// ParseAuthResults parses a Authentication-Results header value.

133//

134// Comments are not populated in the returned AuthResults.

135// Both crlf and lf line-endings are accepted. The input string must end with

136// either crlf or lf.

137func ParseAuthResults(s string) (ar AuthResults, err error) {

138 // ../rfc/8601:577

139 lower := make([]byte, len(s))

140 for i, c := range []byte(s) {

141 if c >= 'A' && c <= 'Z' {

142 c += 'a' - 'A'

143 }

144 lower[i] = c

145 }

146 p := &parser{s: s, lower: string(lower)}

147 defer p.recover(&err)

148

149 p.cfws()

150 ar.Hostname = p.xvalue()

151 p.cfws()

152 ar.Version = p.digits()

153 p.cfws()

154 for {

155 p.xtake(";")

156 p.cfws()

157 // Yahoo has ";" at the end of the header value, incorrect.

158 if !Pedantic && p.end() {

159 break

160 }

161 method := p.xkeyword(false)

162 p.cfws()

163 if method == "none" {

164 if len(ar.Methods) == 0 {

165 p.xerrorf("missing results")

166 }

167 if !p.end() {

168 p.xerrorf(`data after "none" result`)

169 }

170 return

171 }

172 ar.Methods = append(ar.Methods, p.xresinfo(method))

173 p.cfws()

174 if p.end() {

175 break

176 }

177 }

178 return

179}

180

181type parser struct {

182 s string

183 lower string // Like s, but with ascii characters lower-cased (utf-8 offsets preserved).

184 o int

185}

186

187type parseError struct{ err error }

188

189func (p *parser) recover(err *error) {

190 x := recover()

191 if x == nil {

192 return

193 }

194 perr, ok := x.(parseError)

195 if ok {

196 *err = perr.err

197 return

198 }

199 panic(x)

200}

201

202func (p *parser) xerrorf(format string, args ...any) {

203 panic(parseError{fmt.Errorf(format, args...)})

204}

205

206func (p *parser) end() bool {

207 return p.s[p.o:] == "\r\n" || p.s[p.o:] == "\n"

208}

209

210// ../rfc/5322:599

211func (p *parser) cfws() {

212 p.fws()

213 for p.prefix("(") {

214 p.xcomment()

215 }

216 p.fws()

217}

218

219func (p *parser) fws() {

220 for p.take(" ") || p.take("\t") {

221 }

222 opts := []string{"\n ", "\n\t", "\r\n ", "\r\n\t"}

223 for _, o := range opts {

224 if p.take(o) {

225 break

226 }

227 }

228 for p.take(" ") || p.take("\t") {

229 }

230}

231

232func (p *parser) xcomment() {

233 p.xtake("(")

234 p.fws()

235 for !p.take(")") {

236 if p.empty() {

237 p.xerrorf("unexpected end in comment")

238 }

239 if p.prefix("(") {

240 p.xcomment()

241 p.fws()

242 continue

243 }

244 p.take(`\`)

245 if c := p.s[p.o]; c > ' ' && c < 0x7f {

246 p.o++

247 } else {

248 p.xerrorf("bad character %c in comment", c)

249 }

250 p.fws()

251 }

252}

253

254func (p *parser) prefix(s string) bool {

255 return strings.HasPrefix(p.lower[p.o:], s)

256}

257

258func (p *parser) xvalue() string {

259 if p.prefix(`"`) {

260 return p.xquotedString()

261 }

262 return p.xtakefn1("value token", func(c rune, i int) bool {

263 // ../rfc/2045:661

264 // todo: token cannot contain utf-8? not updated in ../rfc/6532. however, we also use it for the localpart & domain parsing, so we'll allow it.

265 return c > ' ' && !strings.ContainsRune(`()<>@,;:\\"/[]?= `, c)

266 })

267}

268

269func (p *parser) xchar() rune {

270 // We are careful to track invalid utf-8 properly.

271 if p.empty() {

272 p.xerrorf("need another character")

273 }

274 var r rune

275 var o int

276 for i, c := range p.s[p.o:] {

277 if i > 0 {

278 o = i

279 break

280 }

281 r = c

282 }

283 if o == 0 {

284 p.o = len(p.s)

285 } else {

286 p.o += o

287 }

288 return r

289}

290

291func (p *parser) xquotedString() string {

292 p.xtake(`"`)

293 var s string

294 var esc bool

295 for {

296 c := p.xchar()

297 if esc {

298 if c >= ' ' && c < 0x7f {

299 s += string(c)

300 esc = false

301 continue

302 }

303 p.xerrorf("bad escaped char %c in quoted string", c)

304 }

305 if c == '\\' {

306 esc = true

307 continue

308 }

309 if c == '"' {

310 return s

311 }

312 if c >= ' ' && c != '\\' && c != '"' {

313 s += string(c)

314 continue

315 }

316 p.xerrorf("invalid quoted string, invalid character %c", c)

317 }

318}

319

320func (p *parser) digits() string {

321 o := p.o

322 for o < len(p.s) && p.s[o] >= '0' && p.s[o] <= '9' {

323 o++

324 }

325 p.o = o

326 return p.s[o:p.o]

327}

328

329func (p *parser) xdigits() string {

330 s := p.digits()

331 if s == "" {

332 p.xerrorf("expected digits, remaining %q", p.s[p.o:])

333 }

334 return s

335}

336

337func (p *parser) xtake(s string) {

338 if !p.prefix(s) {

339 p.xerrorf("expected %q, remaining %q", s, p.s[p.o:])

340 }

341 p.o += len(s)

342}

343

344func (p *parser) empty() bool {

345 return p.o >= len(p.s)

346}

347

348func (p *parser) take(s string) bool {

349 if p.prefix(s) {

350 p.o += len(s)

351 return true

352 }

353 return false

354}

355

356func (p *parser) xtakefn1(what string, fn func(c rune, i int) bool) string {

357 if p.empty() {

358 p.xerrorf("need at least one char for %s", what)

359 }

360 for i, c := range p.s[p.o:] {

361 if !fn(c, i) {

362 if i == 0 {

363 p.xerrorf("expected at least one char for %s, remaining %q", what, p.s[p.o:])

364 }

365 s := p.s[p.o : p.o+i]

366 p.o += i

367 return s

368 }

369 }

370 s := p.s[p.o:]

371 p.o = len(p.s)

372 return s

373}

374

375// ../rfc/5321:2287

376func (p *parser) xkeyword(isResult bool) string {

377 s := strings.ToLower(p.xtakefn1("keyword", func(c rune, i int) bool {

378 // Yahoo sends results like "dkim=perm_fail".

379 return c >= 'a' && c <= 'z' || c >= '0' && c <= '9' || c == '-' || isResult && !Pedantic && c == '_'

380 }))

381 if s == "-" {

382 p.xerrorf("missing keyword")

383 } else if strings.HasSuffix(s, "-") {

384 p.o--

385 s = s[:len(s)-1]

386 }

387 return s

388}

389

390func (p *parser) xmethodspec(methodKeyword string) (string, string, string) {

391 p.cfws()

392 var methodDigits string

393 if p.take("/") {

394 methodDigits = p.xdigits()

395 p.cfws()

396 }

397 p.xtake("=")

398 p.cfws()

399 result := p.xkeyword(true)

400 return methodKeyword, methodDigits, result

401}

402

403func (p *parser) xpropspec() (ap AuthProp) {

404 ap.Type = p.xkeyword(false)

405 p.cfws()

406 p.xtake(".")

407 p.cfws()

408 if p.take("mailfrom") {

409 ap.Property = "mailfrom"

410 } else if p.take("rcptto") {

411 ap.Property = "rcptto"

412 } else {

413 ap.Property = p.xkeyword(false)

414 }

415 p.cfws()

416 p.xtake("=")

417 ap.IsAddrLike, ap.Value = p.xpvalue()

418 return

419}

420

421// method keyword has been parsed, method-version not yet.

422func (p *parser) xresinfo(methodKeyword string) (am AuthMethod) {

423 p.cfws()

424 am.Method, am.Version, am.Result = p.xmethodspec(methodKeyword)

425 p.cfws()

426 if p.take("reason") {

427 p.cfws()

428 p.xtake("=")

429 p.cfws()

430 am.Reason = p.xvalue()

431 }

432 p.cfws()

433 for !p.prefix(";") && !p.end() {

434 am.Props = append(am.Props, p.xpropspec())

435 p.cfws()

436 }

437 return

438}

439

440// todo: could keep track whether this is a localpart.

441func (p *parser) xpvalue() (bool, string) {

442 p.cfws()

443 if p.take("@") {

444 // Bare domain.

445 dom, _ := p.xdomain()

446 return true, "@" + dom

447 }

448 s := p.xvalue()

449 if p.take("@") {

450 dom, _ := p.xdomain()

451 s += "@" + dom

452 return true, s

453 }

454 return false, s

455}

456

457// ../rfc/5321:2291

458func (p *parser) xdomain() (string, dns.Domain) {

459 s := p.xsubdomain()

460 for p.take(".") {

461 s += "." + p.xsubdomain()

462 }

463 d, err := dns.ParseDomain(s)

464 if err != nil {

465 p.xerrorf("parsing domain name %q: %s", s, err)

466 }

467 if len(s) > 255 {

468 // ../rfc/5321:3491

469 p.xerrorf("domain longer than 255 octets")

470 }

471 return s, d

472}

473

474// ../rfc/5321:2303

475// ../rfc/5321:2303 ../rfc/6531:411

476func (p *parser) xsubdomain() string {

477 return p.xtakefn1("subdomain", func(c rune, i int) bool {

478 return c >= '0' && c <= '9' || c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || i > 0 && c == '-' || c > 0x7f

479 })

480}

481