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93c52b01a0
the smtp extension, rfc 4865. also implement in the webmail. the queueing/delivery part hardly required changes: we just set the first delivery time in the future instead of immediately. still have to find the first client that implements it.
531 lines
12 KiB
Go
531 lines
12 KiB
Go
package smtpserver
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import (
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"errors"
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"fmt"
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"net"
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"strconv"
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"strings"
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"time"
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"github.com/mjl-/mox/dns"
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"github.com/mjl-/mox/mox-"
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"github.com/mjl-/mox/smtp"
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)
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// Parser holds the original string and string with ascii a-z upper-cased for easy
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// case-insensitive parsing.
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type parser struct {
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orig string
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upper string
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o int // Offset into orig/upper.
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smtputf8 bool // Whether SMTPUTF8 extension is enabled, making IDNA domains and utf8 localparts valid.
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conn *conn
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utf8LocalpartCode int // If non-zero, error for utf-8 localpart when smtputf8 not enabled.
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}
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// toUpper upper cases bytes that are a-z. strings.ToUpper does too much. and
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// would replace invalid bytes with unicode replacement characters, which would
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// break our requirement that offsets into the original and upper case strings
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// point to the same character.
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func toUpper(s string) string {
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r := []byte(s)
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for i, c := range r {
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if c >= 'a' && c <= 'z' {
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r[i] = c - 0x20
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}
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}
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return string(r)
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}
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func newParser(s string, smtputf8 bool, conn *conn) *parser {
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return &parser{orig: s, upper: toUpper(s), smtputf8: smtputf8, conn: conn}
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}
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func (p *parser) xerrorf(format string, args ...any) {
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// For submission, send the remaining unparsed line. Otherwise, only log it.
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var err error
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errmsg := "bad syntax: " + fmt.Sprintf(format, args...)
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remaining := fmt.Sprintf(" (remaining %q)", p.orig[p.o:])
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if p.conn.account != nil {
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errmsg += remaining
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err = errors.New(errmsg)
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} else {
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err = errors.New(errmsg + remaining)
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}
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// ../rfc/5321:2377
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panic(smtpError{smtp.C501BadParamSyntax, smtp.SeProto5Syntax2, errmsg, err, false, true})
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}
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func (p *parser) xutf8localparterrorf() {
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code := p.utf8LocalpartCode
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if code == 0 {
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code = smtp.C550MailboxUnavail
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}
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// ../rfc/6531:466
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xsmtpUserErrorf(code, smtp.SeMsg6NonASCIIAddrNotPermitted7, "non-ascii address not permitted without smtputf8")
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}
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func (p *parser) empty() bool {
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return p.o == len(p.orig)
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}
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// note: use xend() for check for end of line with remaining white space, to be used by commands.
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func (p *parser) xempty() {
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if p.o != len(p.orig) {
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p.xerrorf("expected end of line")
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}
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}
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// check we are at the end of a command.
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func (p *parser) xend() {
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// For submission, we are strict.
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if p.conn.submission {
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p.xempty()
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}
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// Otherwise we allow trailing white space. ../rfc/5321:1758
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rem := p.remainder()
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for _, c := range rem {
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if c != ' ' && c != '\t' {
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p.xerrorf("trailing data, not white space: %q", rem)
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}
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}
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}
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func (p *parser) hasPrefix(s string) bool {
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return strings.HasPrefix(p.upper[p.o:], s)
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}
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func (p *parser) take(s string) bool {
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if p.hasPrefix(s) {
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p.o += len(s)
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return true
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}
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return false
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}
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func (p *parser) xtake(s string) {
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if !p.take(s) {
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p.xerrorf("expected %q", s)
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}
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}
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func (p *parser) space() bool {
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return p.take(" ")
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}
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func (p *parser) xspace() {
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p.xtake(" ")
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}
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func (p *parser) xtaken(n int) string {
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r := p.orig[p.o : p.o+n]
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p.o += n
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return r
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}
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func (p *parser) remainder() string {
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r := p.orig[p.o:]
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p.o = len(p.orig)
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return r
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}
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func (p *parser) peekchar() rune {
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for _, c := range p.upper[p.o:] {
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return c
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}
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return -1
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}
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func (p *parser) xtakefn1(what string, fn func(c rune, i int) bool) string {
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if p.empty() {
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p.xerrorf("need at least one char for %s", what)
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}
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for i, c := range p.upper[p.o:] {
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if !fn(c, i) {
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if i == 0 {
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p.xerrorf("expected at least one char for %s", what)
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}
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return p.xtaken(i)
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}
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}
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return p.remainder()
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}
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func (p *parser) xtakefn1case(what string, fn func(c rune, i int) bool) string {
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if p.empty() {
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p.xerrorf("need at least one char for %s", what)
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}
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for i, c := range p.orig[p.o:] {
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if !fn(c, i) {
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if i == 0 {
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p.xerrorf("expected at least one char for %s", what)
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}
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return p.xtaken(i)
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}
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}
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return p.remainder()
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}
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func (p *parser) xtakefn(fn func(c rune, i int) bool) string {
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for i, c := range p.upper[p.o:] {
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if !fn(c, i) {
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return p.xtaken(i)
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}
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}
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return p.remainder()
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}
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// xrawReversePath returns the raw string between the <>'s. We cannot parse it
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// immediately, because if this is an IDNA (internationalization) address, we would
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// only see the SMTPUTF8 indicator after having parsed the reverse path here. So we
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// parse the raw data here, and validate it after having seen all parameters.
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// ../rfc/5321:2260
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func (p *parser) xrawReversePath() string {
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p.xtake("<")
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s := p.xtakefn(func(c rune, i int) bool {
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return c != '>'
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})
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p.xtake(">")
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return s
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}
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// xbareReversePath parses a reverse-path without <>, as returned by
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// xrawReversePath. It takes smtputf8 into account.
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// ../rfc/5321:2260
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func (p *parser) xbareReversePath() smtp.Path {
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if p.empty() {
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return smtp.Path{}
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}
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// ../rfc/6531:468
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p.utf8LocalpartCode = smtp.C550MailboxUnavail
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defer func() {
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p.utf8LocalpartCode = 0
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}()
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return p.xbarePath()
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}
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func (p *parser) xforwardPath() smtp.Path {
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// ../rfc/6531:466
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p.utf8LocalpartCode = smtp.C553BadMailbox
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defer func() {
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p.utf8LocalpartCode = 0
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}()
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return p.xpath()
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}
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// ../rfc/5321:2264
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func (p *parser) xpath() smtp.Path {
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o := p.o
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p.xtake("<")
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r := p.xbarePath()
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p.xtake(">")
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if p.o-o > 256 {
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// ../rfc/5321:3495
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p.xerrorf("path longer than 256 octets")
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}
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return r
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}
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func (p *parser) xbarePath() smtp.Path {
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// We parse but ignore any source routing.
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// ../rfc/5321:1081 ../rfc/5321:1430 ../rfc/5321:1925
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if p.take("@") {
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p.xdomain()
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for p.take(",") {
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p.xtake("@")
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p.xdomain()
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}
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p.xtake(":")
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}
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return p.xmailbox()
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}
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// ../rfc/5321:2291
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func (p *parser) xdomain() dns.Domain {
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s := p.xsubdomain()
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for p.take(".") {
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s += "." + p.xsubdomain()
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}
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d, err := dns.ParseDomain(s)
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if err != nil {
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p.xerrorf("parsing domain name %q: %s", s, err)
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}
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if len(s) > 255 {
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// ../rfc/5321:3491
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p.xerrorf("domain longer than 255 octets")
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}
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return d
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}
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// ../rfc/5321:2303
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// ../rfc/5321:2303 ../rfc/6531:411
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func (p *parser) xsubdomain() string {
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return p.xtakefn1("subdomain", func(c rune, i int) bool {
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return c >= '0' && c <= '9' || c >= 'A' && c <= 'Z' || i > 0 && c == '-' || c > 0x7f && p.smtputf8
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})
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}
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// ../rfc/5321:2314
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func (p *parser) xmailbox() smtp.Path {
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localpart := p.xlocalpart()
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p.xtake("@")
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return smtp.Path{Localpart: localpart, IPDomain: p.xipdomain(false)}
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}
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// ../rfc/5321:2307
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func (p *parser) xldhstr() string {
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return p.xtakefn1("ldh-str", func(c rune, i int) bool {
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return c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || i == 0 && c == '-'
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})
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}
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// parse address-literal or domain.
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func (p *parser) xipdomain(isehlo bool) dns.IPDomain {
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// ../rfc/5321:2309
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// ../rfc/5321:2397
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if p.take("[") {
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c := p.peekchar()
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var ipv6 bool
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if !(c >= '0' && c <= '9') {
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addrlit := p.xldhstr()
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p.xtake(":")
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if !strings.EqualFold(addrlit, "IPv6") {
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p.xerrorf("unrecognized address literal %q", addrlit)
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}
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ipv6 = true
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}
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ipaddr := p.xtakefn1("address literal", func(c rune, i int) bool {
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return c != ']'
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})
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p.take("]")
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ip := net.ParseIP(ipaddr)
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if ip == nil {
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p.xerrorf("invalid ip in address: %q", ipaddr)
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}
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isv4 := ip.To4() != nil
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isAllowedSloppyIPv6Submission := func() bool {
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// Mail user agents that submit are relatively likely to use IPs in EHLO and forget
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// that an IPv6 address needs to be tagged as such. We can forgive them. For
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// SMTP servers we are strict.
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return isehlo && p.conn.submission && !mox.Pedantic && ip.To16() != nil
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}
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if ipv6 && isv4 {
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p.xerrorf("ip address is not ipv6")
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} else if !ipv6 && !isv4 && !isAllowedSloppyIPv6Submission() {
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if ip.To16() != nil {
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p.xerrorf("ip address is ipv6, must use syntax [IPv6:...]")
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} else {
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p.xerrorf("ip address is not ipv4")
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}
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}
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return dns.IPDomain{IP: ip}
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}
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return dns.IPDomain{Domain: p.xdomain()}
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}
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// todo: reduce duplication between implementations: ../smtp/address.go:/xlocalpart ../dkim/parser.go:/xlocalpart ../smtpserver/parse.go:/xlocalpart
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func (p *parser) xlocalpart() smtp.Localpart {
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// ../rfc/5321:2316
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var s string
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if p.hasPrefix(`"`) {
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s = p.xquotedString(true)
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} else {
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s = p.xatom(true)
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for p.take(".") {
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s += "." + p.xatom(true)
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}
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}
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// In the wild, some services use large localparts for generated (bounce) addresses.
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if mox.Pedantic && len(s) > 64 || len(s) > 128 {
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// ../rfc/5321:3486
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p.xerrorf("localpart longer than 64 octets")
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}
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return smtp.Localpart(s)
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}
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// ../rfc/5321:2324
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func (p *parser) xquotedString(islocalpart bool) string {
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p.xtake(`"`)
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var s string
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var esc bool
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for {
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c := p.xchar()
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if esc {
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if c >= ' ' && c < 0x7f {
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s += string(c)
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esc = false
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continue
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}
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p.xerrorf("invalid localpart, bad escaped char %c", c)
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}
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if c == '\\' {
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esc = true
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continue
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}
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if c == '"' {
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return s
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}
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// ../rfc/5321:2332 ../rfc/6531:419
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if islocalpart && c > 0x7f && !p.smtputf8 {
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p.xutf8localparterrorf()
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}
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if c >= ' ' && c < 0x7f && c != '\\' && c != '"' || (c > 0x7f && p.smtputf8) {
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s += string(c)
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continue
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}
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p.xerrorf("invalid localpart, invalid character %c", c)
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}
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}
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func (p *parser) xchar() rune {
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// We are careful to track invalid utf-8 properly.
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if p.empty() {
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p.xerrorf("need another character")
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}
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var r rune
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var o int
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for i, c := range p.orig[p.o:] {
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if i > 0 {
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o = i
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break
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}
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r = c
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}
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if o == 0 {
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p.o = len(p.orig)
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} else {
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p.o += o
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}
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return r
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}
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// ../rfc/5321:2320 ../rfc/6531:414
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func (p *parser) xatom(islocalpart bool) string {
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return p.xtakefn1("atom", func(c rune, i int) bool {
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switch c {
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case '!', '#', '$', '%', '&', '\'', '*', '+', '-', '/', '=', '?', '^', '_', '`', '{', '|', '}', '~':
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return true
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}
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if islocalpart && c > 0x7f && !p.smtputf8 {
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p.xutf8localparterrorf()
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}
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return c >= '0' && c <= '9' || c >= 'A' && c <= 'Z' || (c > 0x7f && p.smtputf8)
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})
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}
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// ../rfc/5321:2338
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func (p *parser) xstring() string {
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if p.peekchar() == '"' {
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return p.xquotedString(false)
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}
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return p.xatom(false)
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}
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// ../rfc/5321:2279
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func (p *parser) xparamKeyword() string {
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return p.xtakefn1("parameter keyword", func(c rune, i int) bool {
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return c >= '0' && c <= '9' || c >= 'A' && c <= 'Z' || (i > 0 && c == '-')
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})
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}
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// ../rfc/5321:2281 ../rfc/6531:422
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func (p *parser) xparamValue() string {
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return p.xtakefn1("parameter value", func(c rune, i int) bool {
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return c > ' ' && c < 0x7f && c != '=' || (c > 0x7f && p.smtputf8)
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})
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}
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// for smtp parameters that take a numeric parameter with specified number of
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// digits, eg SIZE=... for MAIL FROM.
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func (p *parser) xnumber(maxDigits int, allowZero bool) int64 {
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s := p.xtakefn1("number", func(c rune, i int) bool {
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return (c >= '1' && c <= '9' || c == '0' && (i > 0 || allowZero)) && i < maxDigits
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})
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v, err := strconv.ParseInt(s, 10, 64)
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if err != nil {
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p.xerrorf("bad number %q: %s", s, err)
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}
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return v
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}
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// parse date-time in UTC form. ../rfc/4865:147 ../rfc/4865-eid2040
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func (p *parser) xdatetimeutc() (time.Time, string) {
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// ../rfc/3339:422
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xdash := func() string {
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p.xtake("-")
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return "-"
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}
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xcolon := func() string {
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p.xtake(":")
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return ":"
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}
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xdigits := func(n int) string {
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s := p.xtakefn1("digits", func(c rune, i int) bool {
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return c >= '0' && c <= '9' && i < n
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})
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if len(s) != n {
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p.xerrorf("parsing date-time: got %d digits, need %d", len(s), n)
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}
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return s
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}
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s := xdigits(4) + xdash() + xdigits(2) + xdash() + xdigits(2)
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if !p.hasPrefix("T") {
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p.xerrorf("expected T for date-time separator")
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}
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s += p.xtaken(1) + xdigits(2) + xcolon() + xdigits(2) + xcolon() + xdigits(2)
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layout := time.RFC3339
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if p.take(".") {
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layout = time.RFC3339Nano
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s += "." + p.xtakefn1("digits", func(c rune, i int) bool {
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return c >= '0' && c <= '9'
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})
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}
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if !p.hasPrefix("Z") {
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p.xerrorf("expected Z for date-time utc timezone")
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}
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s += p.xtaken(1)
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t, err := time.Parse(layout, s)
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if err != nil {
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p.xerrorf("bad utc date-time %q: %s", s, err)
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}
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return t, s
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}
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|
// sasl mechanism, for AUTH command.
|
|
// ../rfc/4422:436
|
|
func (p *parser) xsaslMech() string {
|
|
return p.xtakefn1case("sasl-mech", func(c rune, i int) bool {
|
|
return i < 20 && (c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c == '-' || c == '_')
|
|
})
|
|
}
|
|
|
|
// ../rfc/4954:696 ../rfc/6533:259
|
|
func (p *parser) xtext() string {
|
|
r := ""
|
|
for !p.empty() {
|
|
b := p.orig[p.o]
|
|
if b >= 0x21 && b < 0x7f && b != '+' && b != '=' && b != ' ' {
|
|
r += string(b)
|
|
p.xtaken(1)
|
|
continue
|
|
}
|
|
if b != '+' {
|
|
break
|
|
}
|
|
p.xtaken(1)
|
|
x := p.xtaken(2)
|
|
for _, b := range x {
|
|
if b >= '0' && b <= '9' || b >= 'A' && b <= 'F' {
|
|
continue
|
|
}
|
|
p.xerrorf("parsing xtext: invalid hexadecimal %q", x)
|
|
}
|
|
const hex = "0123456789ABCDEF"
|
|
b = byte(strings.IndexByte(hex, x[0])<<4) | byte(strings.IndexByte(hex, x[1])<<0)
|
|
r += string(rune(b))
|
|
}
|
|
return r
|
|
}
|