package dns import ( "bytes" "fmt" "io" "strconv" "strings" ) // Parse the $GENERATE statement as used in BIND9 zones. // See http://www.zytrax.com/books/dns/ch8/generate.html for instance. // We are called after '$GENERATE '. After which we expect: // * the range (12-24/2) // * lhs (ownername) // * [[ttl][class]] // * type // * rhs (rdata) // But we are lazy here, only the range is parsed *all* occurrences // of $ after that are interpreted. func (zp *ZoneParser) generate(l lex) (RR, bool) { token := l.token step := int64(1) if i := strings.IndexByte(token, '/'); i >= 0 { if i+1 == len(token) { return zp.setParseError("bad step in $GENERATE range", l) } s, err := strconv.ParseInt(token[i+1:], 10, 64) if err != nil || s <= 0 { return zp.setParseError("bad step in $GENERATE range", l) } step = s token = token[:i] } startStr, endStr, ok := strings.Cut(token, "-") if !ok { return zp.setParseError("bad start-stop in $GENERATE range", l) } start, err := strconv.ParseInt(startStr, 10, 64) if err != nil { return zp.setParseError("bad start in $GENERATE range", l) } end, err := strconv.ParseInt(endStr, 10, 64) if err != nil { return zp.setParseError("bad stop in $GENERATE range", l) } if end < 0 || start < 0 || end < start || (end-start)/step > 65535 { return zp.setParseError("bad range in $GENERATE range", l) } // _BLANK l, ok = zp.c.Next() if !ok || l.value != zBlank { return zp.setParseError("garbage after $GENERATE range", l) } // Create a complete new string, which we then parse again. var s string for l, ok := zp.c.Next(); ok; l, ok = zp.c.Next() { if l.err { return zp.setParseError("bad data in $GENERATE directive", l) } if l.value == zNewline { break } s += l.token } r := &generateReader{ s: s, cur: start, start: start, end: end, step: step, file: zp.file, lex: &l, } zp.sub = NewZoneParser(r, zp.origin, zp.file) zp.sub.includeDepth, zp.sub.includeAllowed = zp.includeDepth, zp.includeAllowed zp.sub.generateDisallowed = true zp.sub.SetDefaultTTL(defaultTtl) return zp.subNext() } type generateReader struct { s string si int cur int64 start int64 end int64 step int64 mod bytes.Buffer escape bool eof bool file string lex *lex } func (r *generateReader) parseError(msg string, end int) *ParseError { r.eof = true // Make errors sticky. l := *r.lex l.token = r.s[r.si-1 : end] l.column += r.si // l.column starts one zBLANK before r.s return &ParseError{r.file, msg, l} } func (r *generateReader) Read(p []byte) (int, error) { // NewZLexer, through NewZoneParser, should use ReadByte and // not end up here. panic("not implemented") } func (r *generateReader) ReadByte() (byte, error) { if r.eof { return 0, io.EOF } if r.mod.Len() > 0 { return r.mod.ReadByte() } if r.si >= len(r.s) { r.si = 0 r.cur += r.step r.eof = r.cur > r.end || r.cur < 0 return '\n', nil } si := r.si r.si++ switch r.s[si] { case '\\': if r.escape { r.escape = false return '\\', nil } r.escape = true return r.ReadByte() case '$': if r.escape { r.escape = false return '$', nil } mod := "%d" if si >= len(r.s)-1 { // End of the string fmt.Fprintf(&r.mod, mod, r.cur) return r.mod.ReadByte() } if r.s[si+1] == '$' { r.si++ return '$', nil } var offset int64 // Search for { and } if r.s[si+1] == '{' { // Modifier block sep := strings.Index(r.s[si+2:], "}") if sep < 0 { return 0, r.parseError("bad modifier in $GENERATE", len(r.s)) } var errMsg string mod, offset, errMsg = modToPrintf(r.s[si+2 : si+2+sep]) if errMsg != "" { return 0, r.parseError(errMsg, si+3+sep) } if r.start+offset < 0 || r.end+offset > 1<<31-1 { return 0, r.parseError("bad offset in $GENERATE", si+3+sep) } r.si += 2 + sep // Jump to it } fmt.Fprintf(&r.mod, mod, r.cur+offset) return r.mod.ReadByte() default: if r.escape { // Pretty useless here r.escape = false return r.ReadByte() } return r.s[si], nil } } // Convert a $GENERATE modifier 0,0,d to something Printf can deal with. func modToPrintf(s string) (string, int64, string) { // Modifier is { offset [ ,width [ ,base ] ] } - provide default // values for optional width and type, if necessary. offStr, s, ok0 := strings.Cut(s, ",") widthStr, s, ok1 := strings.Cut(s, ",") base, _, ok2 := strings.Cut(s, ",") if !ok0 { widthStr = "0" } if !ok1 { base = "d" } if ok2 { return "", 0, "bad modifier in $GENERATE" } switch base { case "o", "d", "x", "X": default: return "", 0, "bad base in $GENERATE" } offset, err := strconv.ParseInt(offStr, 10, 64) if err != nil { return "", 0, "bad offset in $GENERATE" } width, err := strconv.ParseUint(widthStr, 10, 8) if err != nil { return "", 0, "bad width in $GENERATE" } if width == 0 { return "%" + base, offset, "" } return "%0" + widthStr + base, offset, "" }