Added header User Agent decoding (prebid#1268)

* Added header User Agent decoding

* Added header User Agent decoding: unit tests

* Added header User Agent decoding: unit tests

* Added check UA is encoded to avoid `+` converted to space

Co-authored-by: Veronika Solovei <veronika.solovei@xandr.com>

endpoints/openrtb2/video_auction.go

@@ -8,12 +8,13 @@ import (
 	"io"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"strconv"
 	"strings"
 	"time"
 
 	"github.com/buger/jsonparser"
-	jsonpatch "github.com/evanphx/json-patch"
+	"github.com/evanphx/json-patch"
 	"github.com/gofrs/uuid"
 	"github.com/prebid/prebid-server/errortypes"
 
@@ -617,7 +618,18 @@ func (deps *endpointDeps) parseVideoRequest(request []byte, headers http.Header)
 
 	//if Device.UA is not present in request body, init it with user-agent from request header if it's present
 	if req.Device.UA == "" {
-		req.Device.UA = headers.Get("User-Agent")
+		ua := headers.Get("User-Agent")
+
+		//Check UA is encoded. Without it the `+` character would get changed to a space if not actually encoded
+		if strings.ContainsAny(ua, "%") {
+			var err error
+			req.Device.UA, err = url.QueryUnescape(ua)
+			if err != nil {
+				req.Device.UA = ua
+			}
+		} else {
+			req.Device.UA = ua
+		}
 	}
 
 	errL, podErrors := deps.validateVideoRequest(req)

endpoints/openrtb2/video_auction_test.go

@@ -927,6 +927,49 @@ func TestParseVideoRequestWithoutUserAgentAndEmptyHeader(t *testing.T) {
 
 }
 
+func TestParseVideoRequestWithEncodedUserAgentInHeader(t *testing.T) {
+	ex := &mockExchangeVideo{}
+	reqData, err := ioutil.ReadFile("sample-requests/video/video_valid_sample_without_device_user_agent.json")
+	if err != nil {
+		t.Fatalf("Failed to fetch a valid request: %v", err)
+	}
+
+	uaEncoded := "Mozilla%2F5.0%20%28Macintosh%3B%20Intel%20Mac%20OS%20X%2010_14_6%29%20AppleWebKit%2F537.36%20%28KHTML%2C%20like%20Gecko%29%20Chrome%2F78.0.3904.87%20Safari%2F537.36"
+	uaDecoded := "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36"
+
+	headers := http.Header{}
+	headers.Add("User-Agent", uaEncoded)
+
+	deps := mockDeps(t, ex)
+	req, valErr, podErr := deps.parseVideoRequest(reqData, headers)
+
+	assert.Equal(t, uaDecoded, req.Device.UA, "Device.ua should be taken from request header")
+	assert.Equal(t, []error(nil), valErr, "No validation errors should be returned")
+	assert.Equal(t, make([]PodError, 0), podErr, "No pod errors should be returned")
+
+}
+
+func TestParseVideoRequestWithDecodedUserAgentInHeader(t *testing.T) {
+	ex := &mockExchangeVideo{}
+	reqData, err := ioutil.ReadFile("sample-requests/video/video_valid_sample_without_device_user_agent.json")
+	if err != nil {
+		t.Fatalf("Failed to fetch a valid request: %v", err)
+	}
+
+	uaDecoded := "Mozilla/5.0+(Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36"
+
+	headers := http.Header{}
+	headers.Add("User-Agent", uaDecoded)
+
+	deps := mockDeps(t, ex)
+	req, valErr, podErr := deps.parseVideoRequest(reqData, headers)
+
+	assert.Equal(t, uaDecoded, req.Device.UA, "Device.ua should be taken from request header")
+	assert.Equal(t, []error(nil), valErr, "No validation errors should be returned")
+	assert.Equal(t, make([]PodError, 0), podErr, "No pod errors should be returned")
+
+}
+
 func TestHandleErrorDebugLog(t *testing.T) {
 	vo := analytics.VideoObject{
 		Status: 200,