Sync with mattermost 3.1.0

vendor/github.com/mattermost/platform/model/incoming_webhook.go

@@ -4,13 +4,15 @@
 package model
 
 import (
+	"bytes"
 	"encoding/json"
 	"io"
+	"regexp"
+	"strings"
 )
 
 const (
 	DEFAULT_WEBHOOK_USERNAME = "webhook"
-	DEFAULT_WEBHOOK_ICON     = "/static/images/webhook_icon.jpg"
 )
 
 type IncomingWebhook struct {
@@ -125,13 +127,136 @@ func (o *IncomingWebhook) PreUpdate() {
 	o.UpdateAt = GetMillis()
 }
 
-func IncomingWebhookRequestFromJson(data io.Reader) *IncomingWebhookRequest {
-	decoder := json.NewDecoder(data)
+// escapeControlCharsFromPayload escapes control chars (\n, \t) from a byte slice.
+// Context:
+// JSON strings are not supposed to contain control characters such as \n, \t,
+// ... but some incoming webhooks might still send invalid JSON and we want to
+// try to handle that. An example invalid JSON string from an incoming webhook
+// might look like this (strings for both "text" and "fallback" attributes are
+// invalid JSON strings because they contain unescaped newlines and tabs):
+//  `{
+//    "text": "this is a test
+//						 that contains a newline and tabs",
+//    "attachments": [
+//      {
+//        "fallback": "Required plain-text summary of the attachment
+//										that contains a newline and tabs",
+//        "color": "#36a64f",
+//  			...
+//        "text": "Optional text that appears within the attachment
+//								 that contains a newline and tabs",
+//  			...
+//        "thumb_url": "http://example.com/path/to/thumb.png"
+//      }
+//    ]
+//  }`
+// This function will search for `"key": "value"` pairs, and escape \n, \t
+// from the value.
+func escapeControlCharsFromPayload(by []byte) []byte {
+	// we'll search for `"text": "..."` or `"fallback": "..."`, ...
+	keys := "text|fallback|pretext|author_name|title|value"
+
+	// the regexp reads like this:
+	// (?s): this flag let . match \n (default is false)
+	// "(keys)": we search for the keys defined above
+	// \s*:\s*: followed by 0..n spaces/tabs, a colon then 0..n spaces/tabs
+	// ": a double-quote
+	// (\\"|[^"])*: any number of times the `\"` string or any char but a double-quote
+	// ": a double-quote
+	r := `(?s)"(` + keys + `)"\s*:\s*"(\\"|[^"])*"`
+	re := regexp.MustCompile(r)
+
+	// the function that will escape \n and \t on the regexp matches
+	repl := func(b []byte) []byte {
+		if bytes.Contains(b, []byte("\n")) {
+			b = bytes.Replace(b, []byte("\n"), []byte("\\n"), -1)
+		}
+		if bytes.Contains(b, []byte("\t")) {
+			b = bytes.Replace(b, []byte("\t"), []byte("\\t"), -1)
+		}
+
+		return b
+	}
+
+	return re.ReplaceAllFunc(by, repl)
+}
+
+func decodeIncomingWebhookRequest(by []byte) (*IncomingWebhookRequest, error) {
+	decoder := json.NewDecoder(bytes.NewReader(by))
 	var o IncomingWebhookRequest
 	err := decoder.Decode(&o)
 	if err == nil {
-		return &o
+		return &o, nil
 	} else {
-		return nil
+		return nil, err
 	}
 }
+
+// To mention @channel via a webhook in Slack, the message should contain
+// <!channel>, as explained at the bottom of this article:
+// https://get.slack.help/hc/en-us/articles/202009646-Making-announcements
+func expandAnnouncement(text string) string {
+	c1 := "<!channel>"
+	c2 := "@channel"
+	if strings.Contains(text, c1) {
+		return strings.Replace(text, c1, c2, -1)
+	}
+	return text
+}
+
+// Expand announcements in incoming webhooks from Slack. Those announcements
+// can be found in the text attribute, or in the pretext, text, title and value
+// attributes of the attachment structure. The Slack attachment structure is
+// documented here: https://api.slack.com/docs/attachments
+func expandAnnouncements(i *IncomingWebhookRequest) {
+	i.Text = expandAnnouncement(i.Text)
+
+	if i.Attachments != nil {
+		attachments := i.Attachments.([]interface{})
+		for _, attachment := range attachments {
+			a := attachment.(map[string]interface{})
+
+			if a["pretext"] != nil {
+				a["pretext"] = expandAnnouncement(a["pretext"].(string))
+			}
+
+			if a["text"] != nil {
+				a["text"] = expandAnnouncement(a["text"].(string))
+			}
+
+			if a["title"] != nil {
+				a["title"] = expandAnnouncement(a["title"].(string))
+			}
+
+			if a["fields"] != nil {
+				fields := a["fields"].([]interface{})
+				for _, field := range fields {
+					f := field.(map[string]interface{})
+					if f["value"] != nil {
+						f["value"] = expandAnnouncement(f["value"].(string))
+					}
+				}
+			}
+		}
+	}
+}
+
+func IncomingWebhookRequestFromJson(data io.Reader) *IncomingWebhookRequest {
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(data)
+	by := buf.Bytes()
+
+	// Try to decode the JSON data. Only if it fails, try to escape control
+	// characters from the strings contained in the JSON data.
+	o, err := decodeIncomingWebhookRequest(by)
+	if err != nil {
+		o, err = decodeIncomingWebhookRequest(escapeControlCharsFromPayload(by))
+		if err != nil {
+			return nil
+		}
+	}
+
+	expandAnnouncements(o)
+
+	return o
+}