Spec SAS verification and the common key verification framework

Reference implementations:
* 94f664e725
* https://github.com/matrix-org/matrix-react-sdk/pull/2461
* https://github.com/matrix-org/matrix-js-sdk/pull/818
* https://github.com/matrix-org/matrix-react-sdk/pull/2596
* https://github.com/matrix-org/matrix-js-sdk/pull/837

Proposals:
* [MSC1717](https://github.com/matrix-org/matrix-doc/pull/1717)
* [MSC1267](https://github.com/matrix-org/matrix-doc/issues/1267)

No alterations to either proposal have been made intentionally here.

scripts/templating/matrix_templates/sections.py

@@ -18,6 +18,7 @@ import inspect
 import json
 import os
 import logging
+import re
 
 
 logger = logging.getLogger(__name__)
@@ -225,3 +226,19 @@ class MatrixSections(Sections):
                 examples=swagger_def['examples'],
                 title_kind=subtitle_title_char)
         return rendered
+
+    def render_sas_emoji_table(self):
+        emoji = self.units.get("sas_emoji")
+        rendered = ".. csv-table::\n"
+        rendered += "  :header: \"Number\", \"Emoji\", \"Unicode\", \"Description\"\n"
+        rendered += "  :widths: 10, 10, 15, 20\n"
+        rendered += "\n"
+        for row in emoji:
+            rendered += "  %d, \"%s\", \"``%s``\", \"%s\"\n" % (
+                row['number'],
+                row['emoji'],
+                row['unicode'],
+                row['description'],
+            )
+        rendered += "\n"
+        return rendered

scripts/templating/matrix_templates/units.py

@@ -59,6 +59,8 @@ TARGETS = os.path.join(matrix_doc_dir, "specification/targets.yaml")
 ROOM_EVENT = "core-event-schema/room_event.yaml"
 STATE_EVENT = "core-event-schema/state_event.yaml"
 
+SAS_EMOJI_JSON = os.path.join(matrix_doc_dir, "data-definitions/sas-emoji.json")
+
 logger = logging.getLogger(__name__)
 
 # a yaml Loader which loads mappings into OrderedDicts instead of regular
@@ -1088,3 +1090,21 @@ class MatrixUnits(Units):
             "string": git_version,
             "revision": git_commit
         }
+
+    def load_sas_emoji(self):
+        with open(SAS_EMOJI_JSON, 'r', encoding='utf-8') as sas_json:
+            emoji = json.load(sas_json)
+
+            # Verify the emoji matches the unicode
+            for c in emoji:
+                e = c['emoji']
+                logger.info("Checking emoji %s (%s)", e, c['description'])
+                u = re.sub(r'U\+([0-9a-fA-F]+)', lambda m: chr(int(m.group(1), 16)), c['unicode'])
+                if e != u:
+                    raise Exception("Emoji %s should be %s not %s" % (
+                        c['description'],
+                        repr(e),
+                        c['unicode'],
+                    ))
+
+            return emoji