facebook-json: add fb_json_str_escape() to properly escape messages

Fixes issues such as losing messages that include a quote character.

Only escapes the minimum needed to work - control characters,
backslashes and quotes. UTF-8 chars are still valid json, so they are
sent as-is.

3 files changed, 40 insertions, 1 deletions

diff --git a/facebook/facebook-api.c b/facebook/facebook-api.c
index a96175f..6c7fc1d 100644
--- a/facebook/facebook-api.c
+++ b/facebook/facebook-api.c
@@ -956,6 +956,7 @@ void fb_api_message(fb_api_t *api, fb_id_t id, gboolean thread,
 {
     guint64      msgid;
     const gchar *tpfx;
+    gchar       *escaped;
 
     g_return_if_fail(api != NULL);
     g_return_if_fail(msg != NULL);
@@ -963,12 +964,16 @@ void fb_api_message(fb_api_t *api, fb_id_t id, gboolean thread,
     msgid = FB_API_MSGID(g_get_real_time() / 1000, g_random_int());
     tpfx  = thread ? "tfbid_" : "";
 
+    escaped = fb_json_str_escape(msg);
+
     fb_api_publish(api, "/send_message2", "{"
             "\"body\":\"%s\","
             "\"to\":\"%s%" FB_ID_FORMAT "\","
             "\"sender_fbid\":\"%" FB_ID_FORMAT "\","
             "\"msgid\":%" G_GUINT64_FORMAT
-        "}", msg, tpfx, id, api->uid, msgid);
+        "}", escaped, tpfx, id, api->uid, msgid);
+
+    g_free(escaped);
 }
 
 /**
diff --git a/facebook/facebook-json.c b/facebook/facebook-json.c
index 6d26289..70f0b39 100644
--- a/facebook/facebook-json.c
+++ b/facebook/facebook-json.c
@@ -314,3 +314,35 @@ gboolean fb_json_str_chk(const json_value *json, const gchar *name,
     *val = jv->u.string.ptr;
     return TRUE;
 }
+
+/**
+ * Backslash-escapes a string to make it safe for json. The returned string
+ * should be freed with #g_free() when no longer needed.
+ *
+ * @param str The string to escape.
+ *
+ * @return The resulting string, or NULL on error.
+ **/
+gchar *fb_json_str_escape(const gchar *str)
+{
+    GString *out;
+    guint    i;
+
+    g_return_val_if_fail(str != NULL, NULL);
+
+    /* let's overallocate a bit */
+    out = g_string_sized_new(strlen(str) * 2);
+
+    for (i = 0; str[i] != '\0'; i++) {
+        if ((str[i] > 0) && (str[i] < 0x20)) {
+            g_string_append_printf(out, "\\u%04x", str[i]);
+            continue;
+        }
+        if ((str[i] == '"') || (str[i] == '\\')) {
+            g_string_append_c(out, '\\');
+        }
+        g_string_append_c(out, str[i]);
+    }
+
+    return g_string_free(out, FALSE);
+}
diff --git a/facebook/facebook-json.h b/facebook/facebook-json.h
index 1720137..9fecbab 100644
--- a/facebook/facebook-json.h
+++ b/facebook/facebook-json.h
@@ -71,4 +71,6 @@ const gchar *fb_json_str(const json_value *json, const gchar *name);
 gboolean fb_json_str_chk(const json_value *json, const gchar *name,
                          const gchar **val);
 
+gchar *fb_json_str_escape(const gchar *str);
+
 #endif /* _FACEBOOK_JSON_H */