Add fuzzing infrastructure (#1118)

Fix file/fuzz.go build and docs in Makefile.fuzz
Each plugin can add a fuzz.go to join the fuzzing craze.
pkg/fuzz/do.go could be made a lot smarter, but is probably good enough
for starters.

$ make -f Makefile.fuzz <plugin>

will build with go-fuzz-build and then execute a go-fuzz run. Each
plugin's fuzz run uses a per-plugin directory to store the fuzz data.

1 files changed, 48 insertions, 0 deletions

diff --git a/plugin/file/fuzz.go b/plugin/file/fuzz.go
new file mode 100644
index 000000000..6be92fb70
--- /dev/null
+++ b/plugin/file/fuzz.go
@@ -0,0 +1,48 @@
+package file
+
+import (
+	"strings"
+
+	"github.com/coredns/coredns/plugin/pkg/fuzz"
+	"github.com/coredns/coredns/plugin/test"
+)
+
+// Fuzz fuzzes file.
+func Fuzz(data []byte) int {
+	name := "miek.nl."
+	zone, _ := Parse(strings.NewReader(fuzzMiekNL), name, "stdin", 0)
+	f := File{Next: test.ErrorHandler(), Zones: Zones{Z: map[string]*Zone{name: zone}, Names: []string{name}}}
+
+	return fuzz.Do(f, data)
+}
+
+const fuzzMiekNL = `
+$TTL    30M
+$ORIGIN miek.nl.
+@       IN      SOA     linode.atoom.net. miek.miek.nl. (
+                             1282630057 ; Serial
+                             4H         ; Refresh
+                             1H         ; Retry
+                             7D         ; Expire
+                             4H )       ; Negative Cache TTL
+                IN      NS      linode.atoom.net.
+                IN      NS      ns-ext.nlnetlabs.nl.
+                IN      NS      omval.tednet.nl.
+                IN      NS      ext.ns.whyscream.net.
+
+                IN      MX      1  aspmx.l.google.com.
+                IN      MX      5  alt1.aspmx.l.google.com.
+                IN      MX      5  alt2.aspmx.l.google.com.
+                IN      MX      10 aspmx2.googlemail.com.
+                IN      MX      10 aspmx3.googlemail.com.
+
+		IN      A       139.162.196.78
+		IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+
+a               IN      A       139.162.196.78
+                IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+www             IN      CNAME   a
+archive         IN      CNAME   a
+
+srv		IN	SRV     10 10 8080 a.miek.nl.
+mx		IN	MX      10 a.miek.nl.`