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import base64
from typing import List, TypedDict
from cryptography.hazmat.primitives import hashes
from django.http import HttpRequest
class HttpSignature:
"""
Allows for calculation and verification of HTTP signatures
"""
@classmethod
def calculate_digest(cls, data, algorithm="sha-256") -> str:
"""
Calculates the digest header value for a given HTTP body
"""
if algorithm == "sha-256":
digest = hashes.Hash(hashes.SHA256())
digest.update(data)
return "SHA-256=" + base64.b64encode(digest.finalize()).decode("ascii")
else:
raise ValueError(f"Unknown digest algorithm {algorithm}")
@classmethod
def headers_from_request(cls, request: HttpRequest, header_names: List[str]) -> str:
"""
Creates the to-be-signed header payload from a Django request"""
headers = {}
for header_name in header_names:
if header_name == "(request-target)":
value = f"post {request.path}"
elif header_name == "content-type":
value = request.META["CONTENT_TYPE"]
else:
value = request.META[f"HTTP_{header_name.upper()}"]
headers[header_name] = value
return "\n".join(f"{name.lower()}: {value}" for name, value in headers.items())
@classmethod
def parse_signature(cls, signature) -> "SignatureDetails":
bits = {}
for item in signature.split(","):
name, value = item.split("=", 1)
value = value.strip('"')
bits[name.lower()] = value
signature_details: SignatureDetails = {
"headers": bits["headers"].split(),
"signature": base64.b64decode(bits["signature"]),
"algorithm": bits["algorithm"],
"keyid": bits["keyid"],
}
return signature_details
class SignatureDetails(TypedDict):
algorithm: str
headers: List[str]
signature: bytes
keyid: str
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