Expose version information via REST API

/v1/data/system/version will return information similar to:

Version: 0.9.3-dev
Build Commit: c5171ed5-dirty
Build Timestamp: 2018-10-07T02:12:58Z
Build Hostname: JOHNDOE-M-9130

Signed-off-by: repenno <rapenno@gmail.com>
Signed-off-by: Torin Sandall <torinsandall@gmail.com>

server/server.go

@@ -7,6 +7,7 @@ package server
 import (
 	"bytes"
 	"context"
+	"crypto/tls"
 	"encoding/json"
 	"fmt"
 	"html/template"
@@ -21,8 +22,6 @@ import (
 	"sync"
 	"time"
 
-	"crypto/tls"
-
 	"net/url"
 
 	"github.com/gorilla/mux"
@@ -132,6 +131,7 @@ func New() *Server {
 	router.Handle("/metrics", promhttp.HandlerFor(promRegistry, promhttp.HandlerOpts{})).Methods(http.MethodGet)
 	s.registerHandler(router, 0, "/data/{path:.+}", http.MethodPost, promhttp.InstrumentHandlerDuration(v0DataDur, http.HandlerFunc(s.v0DataPost)))
 	s.registerHandler(router, 0, "/data", http.MethodPost, promhttp.InstrumentHandlerDuration(v0DataDur, http.HandlerFunc(s.v0DataPost)))
+	s.registerHandler(router, 1, "/data/system/version", http.MethodGet, promhttp.InstrumentHandlerDuration(v1DataDur, http.HandlerFunc(s.v1VersionGet)))
 	s.registerHandler(router, 1, "/data/system/diagnostics", http.MethodGet, promhttp.InstrumentHandlerDuration(v1DataDur, http.HandlerFunc(s.v1DiagnosticsGet)))
 	s.registerHandler(router, 1, "/data/{path:.+}", http.MethodDelete, promhttp.InstrumentHandlerDuration(v1DataDur, http.HandlerFunc(s.v1DataDelete)))
 	s.registerHandler(router, 1, "/data/{path:.+}", http.MethodPut, promhttp.InstrumentHandlerDuration(v1DataDur, http.HandlerFunc(s.v1DataPut)))
@@ -605,6 +605,46 @@ func (s *Server) v1DiagnosticsGet(w http.ResponseWriter, r *http.Request) {
 	writer.JSON(w, 200, resp, pretty)
 }
 
+func (s *Server) v1VersionGet(w http.ResponseWriter, r *http.Request) {
+
+	code := 200
+
+	opaVersion := `
+{
+  "result": {
+    "Version": "{{.Version}}",
+    "BuildCommit": "{{.BuildCommit}}",
+    "BuildTimestamp": "{{.BuildTimestamp}}",
+    "BuildHostname": "{{.BuildHostname}}"
+  }
+}
+	`
+	tmpl, err := template.New("").Parse(opaVersion)
+	if err != nil {
+		panic(err)
+	}
+
+	var buf bytes.Buffer
+
+	err = tmpl.Execute(&buf, struct {
+		Version        string
+		BuildCommit    string
+		BuildTimestamp string
+		BuildHostname  string
+	}{
+		Version:        version.Version,
+		BuildCommit:    version.Vcs,
+		BuildTimestamp: version.Timestamp,
+		BuildHostname:  version.Hostname,
+	})
+
+	jsonBytes := buf.Bytes()
+
+	headers := w.Header()
+	headers.Add("Content-Type", "application/json")
+	writer.Bytes(w, code, jsonBytes)
+}
+
 func (s *Server) v1CompilePost(w http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
 	pretty := getBoolParam(r.URL, types.ParamPrettyV1, true)

server/server_test.go

@@ -15,6 +15,7 @@ import (
 	"net/http/httptest"
 	"net/http/httputil"
 	"reflect"
+	"regexp"
 	"strings"
 	"testing"
 	"time"
@@ -1207,6 +1208,25 @@ func TestIndexGetCompileError(t *testing.T) {
 	}
 }
 
+func TestVersionGet(t *testing.T) {
+
+	f := newFixture(t)
+
+	get := newReqV1(http.MethodGet, "/data/system/version", "")
+	f.server.Handler.ServeHTTP(f.recorder, get)
+	if f.recorder.Code != 200 {
+		t.Fatalf("Expected 200 OK but got %v", f.recorder)
+		return
+	}
+
+	page := f.recorder.Body.String()
+	var re = regexp.MustCompile(`[\s\S]*Version\b[\s\S]*BuildCommit\b[\s\S]*BuildTimestamp\b[\s\S]*BuildHostname\b`)
+	if !re.MatchString(page) {
+		t.Errorf("Expected page to contain 'version' but got: %v", page)
+		return
+	}
+}
+
 func TestPoliciesPutV1(t *testing.T) {
 	f := newFixture(t)
 	req := newReqV1(http.MethodPut, "/policies/1", testMod)