Add a way to export labels with content matched by the probe

CONFIGURATION.md

@@ -182,9 +182,18 @@ regexp: <regex>,
 [ source_ip_address: <string> ]
 
 # The query sent in the TCP probe and the expected associated response.
-# starttls upgrades TCP connection to TLS.
+# "expect" matches a regular expression;
+# "labels" can define labels which will be exported on metric "probe_expect_info";
+# "send" sends some content;
+# "send" and "labels.value" can contain values matched by "expect" (such as "${1}");
+# "starttls" upgrades TCP connection to TLS.
 query_response:
   [ - [ [ expect: <string> ],
+        [ labels:
+          - [ name: <string>
+              value: <string>
+            ], ...
+        ],
         [ send: <string> ],
         [ starttls: <boolean | default = false> ]
       ], ...

blackbox.yml

@@ -33,6 +33,17 @@ modules:
       query_response:
       - expect: "^SSH-2.0-"
       - send: "SSH-2.0-blackbox-ssh-check"
+  ssh_banner_extract:
+    prober: tcp
+    timeout: 5s
+    tcp:
+      query_response:
+      - expect: "^SSH-2.0-([^ -]+)(?: (.*))?$"
+        labels:
+        - name: ssh_version
+          value: "${1}"
+        - name: ssh_comments
+          value: "${2}"
   irc_banner:
     prober: tcp
     tcp:

config/config.go

@@ -239,10 +239,16 @@ type HeaderMatch struct {
 	AllowMissing bool   `yaml:"allow_missing,omitempty"`
 }
 
+type Label struct {
+	Name  string `yaml:"name,omitempty"`
+	Value string `yaml:"value,omitempty"`
+}
+
 type QueryResponse struct {
-	Expect   Regexp `yaml:"expect,omitempty"`
-	Send     string `yaml:"send,omitempty"`
-	StartTLS bool   `yaml:"starttls,omitempty"`
+	Expect   Regexp  `yaml:"expect,omitempty"`
+	Labels   []Label `yaml:"labels,omitempty"`
+	Send     string  `yaml:"send,omitempty"`
+	StartTLS bool    `yaml:"starttls,omitempty"`
 }
 
 type TCPProbe struct {

prober/tcp.go

@@ -88,6 +88,24 @@ func dialTCP(ctx context.Context, target string, module config.Module, registry
 	return tls.DialWithDialer(dialer, dialProtocol, dialTarget, tlsConfig)
 }
 
+func probeExpectInfo(registry *prometheus.Registry, qr *config.QueryResponse, bytes []byte, match []int) {
+	var names []string
+	var values []string
+	for _, s := range qr.Labels {
+		names = append(names, s.Name)
+		values = append(values, string(qr.Expect.Regexp.Expand(nil, []byte(s.Value), bytes, match)))
+	}
+	metric := prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "probe_expect_info",
+			Help: "Explicit content matched",
+		},
+		names,
+	)
+	registry.MustRegister(metric)
+	metric.WithLabelValues(values...).Set(1)
+}
+
 func ProbeTCP(ctx context.Context, target string, module config.Module, registry *prometheus.Registry, logger log.Logger) bool {
 	probeSSLEarliestCertExpiry := prometheus.NewGauge(sslEarliestCertExpiryGaugeOpts)
 	probeSSLLastChainExpiryTimestampSeconds := prometheus.NewGauge(sslChainExpiryInTimeStampGaugeOpts)
@@ -158,6 +176,9 @@ func ProbeTCP(ctx context.Context, target string, module config.Module, registry
 			}
 			probeFailedDueToRegex.Set(0)
 			send = string(qr.Expect.Regexp.Expand(nil, []byte(send), scanner.Bytes(), match))
+			if qr.Labels != nil {
+				probeExpectInfo(registry, &qr, scanner.Bytes(), match)
+			}
 		}
 		if send != "" {
 			level.Debug(logger).Log("msg", "Sending line", "line", send)

prober/tcp_test.go

@@ -525,8 +525,18 @@ func TestTCPConnectionQueryResponseMatching(t *testing.T) {
 			IPProtocolFallback: true,
 			QueryResponse: []config.QueryResponse{
 				{
-					Expect: config.MustNewRegexp("SSH-2.0-(OpenSSH_6.9p1) Debian-2"),
+					Expect: config.MustNewRegexp("^SSH-2.0-([^ -]+)(?: (.*))?$"),
 					Send:   "CONFIRM ${1}",
+					Labels: []config.Label{
+						{
+							Name:  "ssh_version",
+							Value: "${1}",
+						},
+						{
+							Name:  "ssh_comments",
+							Value: "${2}",
+						},
+					},
 				},
 			},
 		},
@@ -560,6 +570,14 @@ func TestTCPConnectionQueryResponseMatching(t *testing.T) {
 		"probe_failed_due_to_regex": 0,
 	}
 	checkRegistryResults(expectedResults, mfs, t)
+	// Check labels
+	expectedLabels := map[string]map[string]string{
+		"probe_expect_info": {
+			"ssh_version":  "OpenSSH_6.9p1",
+			"ssh_comments": "Debian-2",
+		},
+	}
+	checkRegistryLabels(expectedLabels, mfs, t)
 
 }
 
@@ -683,3 +701,38 @@ func TestPrometheusTimeoutTCP(t *testing.T) {
 	}
 	<-ch
 }
+
+func TestProbeExpectInfo(t *testing.T) {
+	registry := prometheus.NewRegistry()
+	qr := config.QueryResponse{
+		Expect: config.MustNewRegexp("^SSH-2.0-([^ -]+)(?: (.*))?$"),
+		Labels: []config.Label{
+			{
+				Name:  "label1",
+				Value: "got ${1} here",
+			},
+			{
+				Name:  "label2",
+				Value: "${1} on ${2}",
+			},
+		},
+	}
+	bytes := []byte("SSH-2.0-OpenSSH_6.9p1 Debian-2")
+	match := qr.Expect.Regexp.FindSubmatchIndex(bytes)
+
+	probeExpectInfo(registry, &qr, bytes, match)
+
+	mfs, err := registry.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Check labels
+	expectedLabels := map[string]map[string]string{
+		"probe_expect_info": {
+			"label1": "got OpenSSH_6.9p1 here",
+			"label2": "OpenSSH_6.9p1 on Debian-2",
+		},
+	}
+	checkRegistryLabels(expectedLabels, mfs, t)
+
+}