TUN-2748: Insecure randomness vulnerability in github.com/miekg/dns

vendor/github.com/miekg/dns/scan.go

@@ -134,7 +134,7 @@ func ReadRR(r io.Reader, file string) (RR, error) {
 }
 
 // ParseZone reads a RFC 1035 style zonefile from r. It returns
-// *Tokens on the returned channel, each consisting of either a
+// Tokens on the returned channel, each consisting of either a
 // parsed RR and optional comment or a nil RR and an error. The
 // channel is closed by ParseZone when the end of r is reached.
 //
@@ -143,7 +143,8 @@ func ReadRR(r io.Reader, file string) (RR, error) {
 // origin, as if the file would start with an $ORIGIN directive.
 //
 // The directives $INCLUDE, $ORIGIN, $TTL and $GENERATE are all
-// supported.
+// supported. Note that $GENERATE's range support up to a maximum of
+// of 65535 steps.
 //
 // Basic usage pattern when reading from a string (z) containing the
 // zone data:
@@ -203,6 +204,7 @@ func parseZone(r io.Reader, origin, file string, t chan *Token) {
 //
 // The directives $INCLUDE, $ORIGIN, $TTL and $GENERATE are all
 // supported. Although $INCLUDE is disabled by default.
+// Note that $GENERATE's range support up to a maximum of 65535 steps.
 //
 // Basic usage pattern when reading from a string (z) containing the
 // zone data:
@@ -246,6 +248,7 @@ type ZoneParser struct {
 	includeDepth uint8
 
 	includeAllowed bool
+	generateDisallowed bool
 }
 
 // NewZoneParser returns an RFC 1035 style zonefile parser that reads
@@ -503,9 +506,8 @@ func (zp *ZoneParser) Next() (RR, bool) {
 				return zp.setParseError("expecting $TTL value, not this...", l)
 			}
 
-			if e := slurpRemainder(zp.c, zp.file); e != nil {
-				zp.parseErr = e
-				return nil, false
+			if err := slurpRemainder(zp.c); err != nil {
+				return zp.setParseError(err.err, err.lex)
 			}
 
 			ttl, ok := stringToTTL(l.token)
@@ -527,9 +529,8 @@ func (zp *ZoneParser) Next() (RR, bool) {
 				return zp.setParseError("expecting $ORIGIN value, not this...", l)
 			}
 
-			if e := slurpRemainder(zp.c, zp.file); e != nil {
-				zp.parseErr = e
-				return nil, false
+			if err := slurpRemainder(zp.c); err != nil {
+				return zp.setParseError(err.err, err.lex)
 			}
 
 			name, ok := toAbsoluteName(l.token, zp.origin)
@@ -547,6 +548,9 @@ func (zp *ZoneParser) Next() (RR, bool) {
 
 			st = zExpectDirGenerate
 		case zExpectDirGenerate:
+			if zp.generateDisallowed {
+				return zp.setParseError("nested $GENERATE directive not allowed", l)
+			}
 			if l.value != zString {
 				return zp.setParseError("expecting $GENERATE value, not this...", l)
 			}
@@ -650,19 +654,44 @@ func (zp *ZoneParser) Next() (RR, bool) {
 
 			st = zExpectRdata
 		case zExpectRdata:
-			r, e := setRR(*h, zp.c, zp.origin, zp.file)
-			if e != nil {
-				// If e.lex is nil than we have encounter a unknown RR type
-				// in that case we substitute our current lex token
-				if e.lex.token == "" && e.lex.value == 0 {
-					e.lex = l // Uh, dirty
-				}
-
-				zp.parseErr = e
-				return nil, false
+			var rr RR
+			if newFn, ok := TypeToRR[h.Rrtype]; ok && canParseAsRR(h.Rrtype) {
+				rr = newFn()
+				*rr.Header() = *h
+			} else {
+				rr = &RFC3597{Hdr: *h}
 			}
 
-			return r, true
+			_, isPrivate := rr.(*PrivateRR)
+			if !isPrivate && zp.c.Peek().token == "" {
+				// This is a dynamic update rr.
+
+				// TODO(tmthrgd): Previously slurpRemainder was only called
+				// for certain RR types, which may have been important.
+				if err := slurpRemainder(zp.c); err != nil {
+					return zp.setParseError(err.err, err.lex)
+				}
+
+				return rr, true
+			} else if l.value == zNewline {
+				return zp.setParseError("unexpected newline", l)
+			}
+
+			if err := rr.parse(zp.c, zp.origin); err != nil {
+				// err is a concrete *ParseError without the file field set.
+				// The setParseError call below will construct a new
+				// *ParseError with file set to zp.file.
+
+				// If err.lex is nil than we have encounter an unknown RR type
+				// in that case we substitute our current lex token.
+				if err.lex == (lex{}) {
+					return zp.setParseError(err.err, l)
+				}
+
+				return zp.setParseError(err.err, err.lex)
+			}
+
+			return rr, true
 		}
 	}
 
@@ -671,6 +700,18 @@ func (zp *ZoneParser) Next() (RR, bool) {
 	return nil, false
 }
 
+// canParseAsRR returns true if the record type can be parsed as a
+// concrete RR. It blacklists certain record types that must be parsed
+// according to RFC 3597 because they lack a presentation format.
+func canParseAsRR(rrtype uint16) bool {
+	switch rrtype {
+	case TypeANY, TypeNULL, TypeOPT, TypeTSIG:
+		return false
+	default:
+		return true
+	}
+}
+
 type zlexer struct {
 	br io.ByteReader
 
@@ -682,7 +723,8 @@ type zlexer struct {
 	comBuf  string
 	comment string
 
-	l lex
+	l       lex
+	cachedL *lex
 
 	brace  int
 	quote  bool
@@ -748,13 +790,37 @@ func (zl *zlexer) readByte() (byte, bool) {
 	return c, true
 }
 
+func (zl *zlexer) Peek() lex {
+	if zl.nextL {
+		return zl.l
+	}
+
+	l, ok := zl.Next()
+	if !ok {
+		return l
+	}
+
+	if zl.nextL {
+		// Cache l. Next returns zl.cachedL then zl.l.
+		zl.cachedL = &l
+	} else {
+		// In this case l == zl.l, so we just tell Next to return zl.l.
+		zl.nextL = true
+	}
+
+	return l
+}
+
 func (zl *zlexer) Next() (lex, bool) {
 	l := &zl.l
-	if zl.nextL {
+	switch {
+	case zl.cachedL != nil:
+		l, zl.cachedL = zl.cachedL, nil
+		return *l, true
+	case zl.nextL:
 		zl.nextL = false
 		return *l, true
-	}
-	if l.err {
+	case l.err:
 		// Parsing errors should be sticky.
 		return lex{value: zEOF}, false
 	}
@@ -908,6 +974,11 @@ func (zl *zlexer) Next() (lex, bool) {
 				// was inside braces and we delayed adding it until now.
 				com[comi] = ' ' // convert newline to space
 				comi++
+				if comi >= len(com) {
+					l.token = "comment length insufficient for parsing"
+					l.err = true
+					return *l, true
+				}
 			}
 
 			com[comi] = ';'
@@ -1302,18 +1373,18 @@ func locCheckEast(token string, longitude uint32) (uint32, bool) {
 }
 
 // "Eat" the rest of the "line"
-func slurpRemainder(c *zlexer, f string) *ParseError {
+func slurpRemainder(c *zlexer) *ParseError {
 	l, _ := c.Next()
 	switch l.value {
 	case zBlank:
 		l, _ = c.Next()
 		if l.value != zNewline && l.value != zEOF {
-			return &ParseError{f, "garbage after rdata", l}
+			return &ParseError{"", "garbage after rdata", l}
 		}
 	case zNewline:
 	case zEOF:
 	default:
-		return &ParseError{f, "garbage after rdata", l}
+		return &ParseError{"", "garbage after rdata", l}
 	}
 	return nil
 }