zulip/zerver/lib/camo.py

from django.conf import settings
import codecs
import hashlib
import hmac

def generate_camo_url(url: str) -> str:
    encoded_url = url.encode("utf-8")
    encoded_camo_key = settings.CAMO_KEY.encode("utf-8")
    digest = hmac.new(encoded_camo_key, encoded_url, hashlib.sha1).hexdigest()
    hex_encoded_url = codecs.encode(encoded_url, "hex")  # type: ignore # https://github.com/python/typeshed/issues/300
    return "%s/%s" % (digest, hex_encoded_url.decode("utf-8"))

# Encodes the provided URL using the same algorithm used by the camo
# caching https image proxy
def get_camo_url(url: str) -> str:
    # Only encode the url if Camo is enabled
    if settings.CAMO_URI == '':
        return url
    return "%s%s" % (settings.CAMO_URI, generate_camo_url(url))

def is_camo_url_valid(digest: str, url: str) -> bool:
    camo_url = generate_camo_url(url)
    camo_url_digest = camo_url.split('/')[0]
    return camo_url_digest == digest