Merge pull request #225 from projectdiscovery/bugfix-recursive-cname

limit cname recursion
projectdiscovery · Sep 2, 2024 · e9a62fb · e9a62fb
2 parents 86a5a5a + c262211
commit e9a62fb
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Showing 2 changed files with 19 additions and 1 deletion.
diff --git a/client.go b/client.go
@@ -22,7 +22,15 @@ import (
 	sliceutil "github.com/projectdiscovery/utils/slice"
 )
 
-var ErrRetriesExceeded = errors.New("could not resolve, max retries exceeded")
+var ()
+
+var (
+	// DefaultMaxPerCNAMEFollows is the default number of times a CNAME can be followed within a trace
+	DefaultMaxPerCNAMEFollows = 32
+
+	// ErrRetriesExceeded is the error returned when the max retries are exceeded
+	ErrRetriesExceeded = errors.New("could not resolve, max retries exceeded")
+)
 
 var internalRangeCheckerInstance *internalRangeChecker
 
@@ -64,6 +72,10 @@ func NewWithOptions(options Options) (*Client, error) {
 		knownHosts, _ = hostsfile.ParseDefault()
 	}
 
+	if options.MaxPerCNAMEFollows == 0 {
+		options.MaxPerCNAMEFollows = DefaultMaxPerCNAMEFollows
+	}
+
 	httpClient := doh.NewHttpClientWithTimeout(options.Timeout)
 
 	client := Client{
@@ -480,6 +492,7 @@ func (c *Client) Trace(host string, requestType uint16, maxrecursion int) (*Trac
 	msg.SetQuestion(host, requestType)
 	servers := RootDNSServersIPv4
 	seenNS := make(map[string]struct{})
+	seenCName := make(map[string]int)
 	for i := 1; i < maxrecursion; i++ {
 		msg.SetQuestion(host, requestType)
 		dnsdatas, err := c.QueryParallel(host, requestType, servers)
@@ -542,6 +555,10 @@ func (c *Client) Trace(host string, requestType uint16, maxrecursion int) (*Trac
 
 		// follow cname if any
 		if nextCname != "" {
+			seenCName[nextCname]++
+			if seenCName[nextCname] > c.options.MaxPerCNAMEFollows {
+				break
+			}
 			host = nextCname
 		}
 	}

diff --git a/options.go b/options.go
@@ -20,6 +20,7 @@ type Options struct {
 	LocalAddrIP           net.IP
 	LocalAddrPort         uint16
 	ConnectionPoolThreads int
+	MaxPerCNAMEFollows    int
 }
 
 // Returns a net.Addr of a UDP or TCP type depending on whats required