501 lines
11 KiB
Go
501 lines
11 KiB
Go
package dns
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import (
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"fmt"
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"io"
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"strconv"
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"strings"
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)
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// Only used when debugging the parser itself.
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var _DEBUG = true
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// Tokinize a RFC 1035 zone file. The tokenizer will normalize it:
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// * Add ownernames if they are left blank;
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// * Suppress sequences of spaces;
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// * Make each RR fit on one line (NEWLINE is send as last)
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// * Handle comments: ;
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// * Handle braces.
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const (
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// Zonefile
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_EOF = iota // Don't let it start with zero
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_STRING
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_BLANK
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_NEWLINE
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_RRTYPE
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_OWNER
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_CLASS
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_DIRORIGIN // $ORIGIN
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_DIRTTL // $TTL
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_DIRINCLUDE // $INCLUDE
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// Privatekey file
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_VALUE
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_KEY
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_EXPECT_OWNER_DIR // Ownername
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_EXPECT_OWNER_BL // Whitespace after the ownername
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_EXPECT_ANY // Expect rrtype, ttl or class
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_EXPECT_ANY_NOCLASS // Expect rrtype or ttl
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_EXPECT_ANY_NOCLASS_BL // The Whitespace after _EXPECT_ANY_NOCLASS
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_EXPECT_ANY_NOTTL // Expect rrtype or class
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_EXPECT_ANY_NOTTL_BL // Whitespace after _EXPECT_ANY_NOTTL
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_EXPECT_RRTYPE // Expect rrtype
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_EXPECT_RRTYPE_BL // Whitespace BEFORE rrtype
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_EXPECT_RDATA // The first element of the rdata
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_EXPECT_DIRTTL_BL // Space after directive $TTL
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_EXPECT_DIRTTL // Directive $TTL
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)
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// ParseError contains the parse error and the location in the io.Reader
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// where the error occured.
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type ParseError struct {
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err string
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lex lex
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}
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func (e *ParseError) Error() string {
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va := strconv.Itoa(e.lex.value)
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s := e.err + ": `" + e.lex.token + "' (value: " + va + ") at line: " +
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strconv.Itoa(e.lex.line) + " and column: " +
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strconv.Itoa(e.lex.column)
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return s
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}
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type lex struct {
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token string // Text of the token
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err string // Error text when the lexer detects it. Not used by the grammar
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value int // Value: _STRING, _BLANK, etc.
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line int // Line in the file
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column int // Column in the fil
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}
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type Token struct {
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Rr RR // the scanned resource record
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Error *ParseError // when an error occured, this is the specifics
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}
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// NewRR parses the string s and returns the RR contained in there. If the string
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// contains more than one RR, only the first is returned. If an error is detected
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// that error is returned.
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// If the class is not specified, the IN class is assumed. If the TTL is not
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// specified DefaultTtl is assumed.
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func NewRR(s string) (RR, error) {
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t := make(chan Token)
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if s[len(s)-1] != '\n' { // We need a closing newline
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t = ParseZone(strings.NewReader(s + "\n"))
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} else {
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t = ParseZone(strings.NewReader(s))
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}
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r := <-t
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if r.Error != nil {
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return nil, r.Error
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}
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return r.Rr, nil
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}
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// ParseZone reads a RFC 1035 zone from r. It returns each parsed RR or on error
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// on the returned channel. The channel t is closed by ParseZone when the end of r is reached.
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func ParseZone(r io.Reader) chan Token {
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t := make(chan Token)
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go parseZone(r, t)
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return t
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}
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func parseZone(r io.Reader, t chan Token) {
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defer close(t)
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c := make(chan lex)
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// Start the lexer
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go zlexer(r, c)
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// 5 possible beginnings of a line, _ is a space
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// 1. _OWNER _ _RRTYPE -> class/ttl omitted
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// 2. _OWNER _ _STRING _ _RRTYPE -> class omitted
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// 3. _OWNER _ _STRING _ _CLASS _ _RRTYPE -> ttl/class
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// 4. _OWNER _ _CLASS _ _RRTYPE -> ttl omitted
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// 5. _OWNER _ _CLASS _ _STRING _ _RRTYPE -> class/ttl (reversed)
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// After detecting these, we know the _RRTYPE so we can jump to functions
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// handling the rdata for each of these types.
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st := _EXPECT_OWNER_DIR
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var h RR_Header
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var ok bool
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var defttl uint32 = DefaultTtl
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for l := range c {
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if _DEBUG {
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fmt.Printf("[%v]\n", l)
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}
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// Lexer spotted an error already
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if l.err != "" {
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t <- Token{Error: &ParseError{l.err, l}}
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return
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}
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switch st {
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case _EXPECT_OWNER_DIR:
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// We can also expect a directive, like $TTL or $ORIGIN
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h.Ttl = defttl
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h.Class = ClassINET
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switch l.value {
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case _NEWLINE: // Empty line
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st = _EXPECT_OWNER_DIR
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case _OWNER:
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h.Name = l.token
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st = _EXPECT_OWNER_BL
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case _DIRTTL:
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st = _EXPECT_DIRTTL_BL
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default:
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t <- Token{Error: &ParseError{"Error at the start", l}}
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return
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}
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case _EXPECT_DIRTTL_BL:
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if l.value != _BLANK {
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t <- Token{Error: &ParseError{"No blank after $-directive", l}}
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return
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}
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st = _EXPECT_DIRTTL
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case _EXPECT_DIRTTL:
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if l.value != _STRING {
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t <- Token{Error: &ParseError{"Expecting $TTL value, not this...", l}}
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return
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}
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if ttl, ok := stringToTtl(l, t); !ok {
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return
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} else {
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defttl = ttl
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}
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st = _EXPECT_OWNER_DIR
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case _EXPECT_OWNER_BL:
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if l.value != _BLANK {
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t <- Token{Error: &ParseError{"No blank after owner", l}}
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return
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}
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st = _EXPECT_ANY
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case _EXPECT_ANY:
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switch l.value {
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case _RRTYPE:
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h.Rrtype, _ = Str_rr[strings.ToUpper(l.token)]
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st = _EXPECT_RDATA
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case _CLASS:
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h.Class, ok = Str_class[strings.ToUpper(l.token)]
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if !ok {
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t <- Token{Error: &ParseError{"Unknown class", l}}
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return
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}
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st = _EXPECT_ANY_NOCLASS_BL
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case _STRING: // TTL is this case
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if ttl, ok := stringToTtl(l, t); !ok {
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return
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} else {
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h.Ttl = ttl
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}
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st = _EXPECT_ANY_NOTTL_BL
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default:
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t <- Token{Error: &ParseError{"Expecting RR type, TTL or class, not this...", l}}
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return
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}
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case _EXPECT_ANY_NOCLASS_BL:
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if l.value != _BLANK {
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t <- Token{Error: &ParseError{"No blank before NOCLASS", l}}
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return
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}
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st = _EXPECT_ANY_NOCLASS
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case _EXPECT_ANY_NOTTL_BL:
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if l.value != _BLANK {
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t <- Token{Error: &ParseError{"No blank before NOTTL", l}}
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return
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}
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st = _EXPECT_ANY_NOTTL
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case _EXPECT_ANY_NOTTL:
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switch l.value {
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case _CLASS:
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h.Class, ok = Str_class[strings.ToUpper(l.token)]
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if !ok {
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t <- Token{Error: &ParseError{"Unknown class", l}}
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return
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}
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st = _EXPECT_RRTYPE_BL
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case _RRTYPE:
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h.Rrtype, _ = Str_rr[strings.ToUpper(l.token)]
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st = _EXPECT_RDATA
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}
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case _EXPECT_ANY_NOCLASS:
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switch l.value {
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case _STRING: // TTL
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if ttl, ok := stringToTtl(l, t); !ok {
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return
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} else {
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h.Ttl = ttl
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}
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st = _EXPECT_RRTYPE_BL
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case _RRTYPE:
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h.Rrtype, _ = Str_rr[strings.ToUpper(l.token)]
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st = _EXPECT_RDATA
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default:
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t <- Token{Error: &ParseError{"Expecting RR type or TTL, not this...", l}}
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return
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}
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case _EXPECT_RRTYPE_BL:
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if l.value != _BLANK {
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t <- Token{Error: &ParseError{"No blank after", l}}
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return
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}
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st = _EXPECT_RRTYPE
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case _EXPECT_RRTYPE:
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if l.value != _RRTYPE {
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t <- Token{Error: &ParseError{"Unknown RR type", l}}
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return
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}
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h.Rrtype, _ = Str_rr[strings.ToUpper(l.token)]
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st = _EXPECT_RDATA
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case _EXPECT_RDATA:
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// I could save my token here...? l
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r, e := setRR(h, c)
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if e != nil {
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// If e.lex is nil than we have encounter a unknown RR type
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// in that case we substitute our current lex token
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if e.lex.token == "" && e.lex.value == 0 {
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e.lex = l // Uh, dirty
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}
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t <- Token{Error: e}
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return
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}
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t <- Token{Rr: r}
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st = _EXPECT_OWNER_DIR
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}
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}
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}
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func (l lex) String() string {
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switch l.value {
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case _STRING:
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return "S:" + l.token + "$"
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case _BLANK:
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return "_"
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case _NEWLINE:
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return "|\n"
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case _RRTYPE:
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return "R:" + l.token + "$"
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case _OWNER:
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return "O:" + l.token + "$"
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case _CLASS:
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return "C:" + l.token + "$"
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case _DIRTTL:
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return "T:" + l.token + "$"
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}
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return ""
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}
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// zlexer scans the sourcefile and returns tokens on the channel c.
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func zlexer(r io.Reader, c chan lex) {
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var l lex
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defer close(c)
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quote := false
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escape := false
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space := false
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commt := false
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rrtype := false
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owner := true
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brace := 0
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p, q := 0, 0
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buf := make([]byte, 4096)
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n, err := r.Read(buf)
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for err != io.EOF {
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l.column = 0
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l.line = 0
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switch buf[q] {
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case ' ', '\t':
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escape = false
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if commt {
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p++
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break
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}
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if p == q {
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//l.value = _BLANK
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//l.token = " "
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} else if owner {
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// If we have a string and its the first, make it an owner
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l.value = _OWNER
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println(p, q)
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l.token = string(buf[p:q])
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// escape $... start with a \ not a $, so this will work
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if l.token == "$TTL" {
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l.value = _DIRTTL
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}
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if l.token == "$ORIGIN" {
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l.value = _DIRORIGIN
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}
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c <- l
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p = q + 1
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} else {
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l.value = _STRING
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l.token = string(buf[p:q])
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if !rrtype {
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if _, ok := Str_rr[strings.ToUpper(l.token)]; ok {
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l.value = _RRTYPE
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rrtype = true
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}
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if _, ok := Str_class[strings.ToUpper(l.token)]; ok {
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l.value = _CLASS
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}
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}
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c <- l
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p = q + 1
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}
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if !space && !commt {
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l.value = _BLANK
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l.token = " "
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c <- l
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p = q + 1
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}
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if space || commt {
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p++
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}
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owner = false
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space = true
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println("upping", p, q)
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case ';':
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if escape {
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escape = false
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break
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}
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if quote {
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// Inside quoted text we allow ;
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break
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}
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p++
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commt = true
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case '\n':
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// Hmmm, escape newline
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escape = false
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if commt {
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// Reset a comment
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commt = false
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rrtype = false
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p++
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// If not in a brace this ends the comment AND the RR
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if brace == 0 {
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owner = true
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l.value = _NEWLINE
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l.token = "\n"
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c <- l
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p = q + 1
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}
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break
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}
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if p != q {
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l.value = _STRING
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l.token = string(buf[p:q])
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if !rrtype {
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if _, ok := Str_rr[strings.ToUpper(l.token)]; ok {
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l.value = _RRTYPE
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rrtype = true
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}
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}
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c <- l
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p = q + 1
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}
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if brace > 0 {
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l.value = _BLANK
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p++
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if !space {
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c <- l
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p = q + 1
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}
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} else {
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l.value = _NEWLINE
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l.token = "\n"
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c <- l
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p = q + 1
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}
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if l.value == _BLANK {
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space = true
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}
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p = q + 1
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println("hallo")
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commt = false
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rrtype = false
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owner = true
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case '\\':
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if commt {
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p++
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break
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}
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if escape {
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escape = false
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break
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}
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escape = true
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case '"':
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if commt {
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p++
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break
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}
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if escape {
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escape = false
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break
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}
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quote = !quote
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case '(':
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if commt {
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p++
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break
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}
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if escape {
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escape = false
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break
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}
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brace++
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case ')':
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if commt {
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p++
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break
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}
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if escape {
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escape = false
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break
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}
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brace--
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if brace < 0 {
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l.err = "Extra closing brace"
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c <- l
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p = q + 1
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return
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}
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default:
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if commt {
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p++
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break
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}
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escape = false
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space = false
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}
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// tok, err = r.ReadByte() read extra bytes
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q++
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if q > n {
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break
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}
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}
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println("We crashen gewoon hier", p, q)
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// It this need anymore???
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/*
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if p != q {
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// Send remainder
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l.token = string(buf[p:q])
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l.value = _STRING
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c <- l
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}
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*/
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}
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func stringToTtl(l lex, t chan Token) (uint32, bool) {
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if ttl, ok := strconv.Atoi(l.token); ok != nil {
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t <- Token{Error: &ParseError{"Not a TTL", l}}
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return 0, false
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} else {
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return uint32(ttl), true
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}
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panic("not reached")
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}
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