[FIX] http,web,website_*: return the correct Content-Type for images

* = website_profile, website_slides

Before this commit, the returned Content-Type was not always correct, for
example if the image tool was changing the format, which happens when given
a BMP (converted to PNG), or other types being converted to JPEG.

The previous method `force_contenttype` was too specific and it wasn't available
in every controller. It didn't even need to be a controller method because it
didn't use self.

Now we create a generic helper to ease updating headers.
The Content-Type is only updated when it is safe to do. It is especially unsafe
for example for SVG files.

task-1958000
PR: #31811

addons/web/controllers/main.py

@@ -971,11 +971,6 @@ class Binary(http.Controller):
         addons_path = http.addons_manifest['web']['addons_path']
         return open(os.path.join(addons_path, 'web', 'static', 'src', 'img', image), 'rb').read()
 
-    def force_contenttype(self, headers, contenttype='image/png'):
-        dictheaders = dict(headers)
-        dictheaders['Content-Type'] = contenttype
-        return list(dictheaders.items())
-
     @http.route(['/web/content',
         '/web/content/<string:xmlid>',
         '/web/content/<string:xmlid>/<string:filename>',
@@ -1034,14 +1029,13 @@ class Binary(http.Controller):
             return request.env['ir.http']._response_by_status(status, headers, image_base64)
         if not image_base64:
             image_base64 = base64.b64encode(self.placeholder(image=placeholder))
-            headers = self.force_contenttype(headers, contenttype='image/png')
             if not (width or height):
                 width, height = odoo.tools.image_guess_size_from_field_name(field)
 
         image_base64 = image_process(image_base64, (width, height), crop=crop)
 
         content = base64.b64decode(image_base64)
-        headers.append(('Content-Length', len(content)))
+        headers = http.set_safe_image_headers(headers, content)
         response = request.make_response(content, headers)
         response.status_code = status
         return response

addons/website_profile/controllers/main.py

@@ -98,7 +98,7 @@ class WebsiteProfile(http.Controller):
         image_base64 = tools.image_process(image_base64, (width, height), crop=crop)
 
         content = base64.b64decode(image_base64)
-        headers.append(('Content-Length', len(content)))
+        headers = http.set_safe_image_headers(headers, content)
         response = request.make_response(content, headers)
         response.status_code = status
         return response

addons/website_slides/controllers/main.py

@@ -531,7 +531,7 @@ class WebsiteSlides(WebsiteProfile):
         image_base64 = tools.image_process(image_base64, (width, height), crop=crop)
 
         content = base64.b64decode(image_base64)
-        headers.append(('Content-Length', len(content)))
+        headers = http.set_safe_image_headers(headers, content)
         response = request.make_response(content, headers)
         response.status_code = status
         return response

odoo/http.py

@@ -50,6 +50,7 @@ from .service.server import memory_info
 from .service import security, model as service_model
 from .tools.func import lazy_property
 from .tools import ustr, consteq, frozendict, pycompat, unique, date_utils
+from .tools.mimetypes import guess_mimetype
 
 from .modules.module import module_manifest
 
@@ -1617,5 +1618,39 @@ def content_disposition(filename):
 
     return "attachment; filename*=UTF-8''%s" % escaped
 
+
+def set_safe_image_headers(headers, content):
+    """Return new headers based on `headers` but with `Content-Length` and
+    `Content-Type` set appropriately depending on the given `content` only if it
+    is safe to do."""
+    content_type = guess_mimetype(content)
+    safe_types = ['image/jpeg', 'image/png', 'image/gif', 'image/x-icon']
+    if content_type in safe_types:
+        headers = set_header_field(headers, 'Content-Type', content_type)
+    set_header_field(headers, 'Content-Length', len(content))
+    return headers
+
+
+def set_header_field(headers, name, value):
+    """ Return new headers based on `headers` but with `value` set for the
+    header field `name`.
+
+    :param headers: the existing headers
+    :type headers: list of tuples (name, value)
+
+    :param name: the header field name
+    :type name: string
+
+    :param value: the value to set for the `name` header
+    :type value: string
+
+    :return: the updated headers
+    :rtype: list of tuples (name, value)
+    """
+    dictheaders = dict(headers)
+    dictheaders[name] = value
+    return list(dictheaders.items())
+
+
 #  main wsgi handler
 root = Root()