[FIX] base: improve last chance for detection of mimetype

Since we return nosniff header, we need to avoid the magic mimetype.

In case of picture in compute field (eg. image_small on product),there are
no mimetype saved in column, and impossible to detect it from name/extention
because url are like: /web/image/product.product/47/image_small.

So before to arbitrary return default_mimetype, we try to detect it from the
content itself.

This commit continue to fix odoo/odoo@13193

openerp/addons/base/ir/ir_http.py

@@ -22,6 +22,7 @@ import openerp
 import openerp.exceptions
 import openerp.models
 from openerp import http
+from openerp.tools.mimetypes import guess_mimetype
 from openerp.http import request, STATIC_CACHE, content_disposition
 from openerp.modules.module import get_resource_path, get_module_path
 from openerp.osv import osv, orm
@@ -295,7 +296,8 @@ class ir_http(osv.AbstractModel):
                 attach_mimetype = env['ir.attachment'].search_read(domain=[('res_model', '=', model), ('res_id', '=', id), ('res_field', '=', field)], fields=['mimetype'], limit=1)
                 mimetype = attach_mimetype and attach_mimetype[0]['mimetype']
             if not mimetype:
-                mimetype = default_mimetype
+                mimetype = guess_mimetype(base64.b64decode(content), default=default_mimetype)
+
         headers += [('Content-Type', mimetype), ('X-Content-Type-Options', 'nosniff')]
 
         # cache
@@ -308,7 +310,6 @@ class ir_http(osv.AbstractModel):
         # content-disposition default name
         if download:
             headers.append(('Content-Disposition', self.content_disposition(filename)))
-
         return (status, headers, content)
 
 

openerp/tools/mimetypes.py

@@ -103,10 +103,11 @@ _Entry = collections.namedtuple('_Entry', ['mimetype', 'signatures', 'discrimina
 _mime_mappings = (
     # pdf
     _Entry('application/pdf', ['%PDF'], []),
-    # jpg, jpeg, png, gif
+    # jpg, jpeg, png, gif, bmp
     _Entry('image/jpeg', ['\xFF\xD8\xFF\xE0', '\xFF\xD8\xFF\xE2', '\xFF\xD8\xFF\xE3', '\xFF\xD8\xFF\xE1'], []),
     _Entry('image/png', ['\x89PNG\r\n\x1A\n'], []),
     _Entry('image/gif', ['GIF87a', 'GIF89a'], []),
+    _Entry('image/bmp', ['BM'], []),
     # OLECF files in general (Word, Excel, PPT, default to word because why not?)
     _Entry('application/msword', ['\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1', '\x0D\x44\x4F\x43'], [
         _check_olecf
@@ -114,7 +115,7 @@ _mime_mappings = (
     # zip, but will include jar, odt, ods, odp, docx, xlsx, pptx, apk
     _Entry('application/zip', ['PK\x03\x04'], [_check_ooxml, _check_open_container_format]),
 )
-def guess_mimetype(bin_data):
+def guess_mimetype(bin_data, default='application/octet-stream'):
     """ Attempts to guess the mime type of the provided binary data, similar
     to but significantly more limited than libmagic
 
@@ -140,7 +141,7 @@ def guess_mimetype(bin_data):
                 # if no discriminant or no discriminant matches, return
                 # primary mime type
                 return entry.mimetype
-    return 'application/octet-stream'
+    return default
 
 
 try: