294 lines
9.8 KiB
Python
294 lines
9.8 KiB
Python
import base64
|
|
import json
|
|
from typing import Dict, List, Literal, TypedDict
|
|
from urllib.parse import urlparse
|
|
|
|
import httpx
|
|
from cryptography.hazmat.primitives import hashes
|
|
from django.http import HttpRequest
|
|
from django.utils import timezone
|
|
from django.utils.http import http_date, parse_http_date
|
|
from OpenSSL import crypto
|
|
from pyld import jsonld
|
|
|
|
from core.ld import format_date
|
|
|
|
|
|
class VerificationError(BaseException):
|
|
"""
|
|
There was an error with verifying the signature
|
|
"""
|
|
|
|
pass
|
|
|
|
|
|
class VerificationFormatError(VerificationError):
|
|
"""
|
|
There was an error with the format of the signature (not if it is valid)
|
|
"""
|
|
|
|
pass
|
|
|
|
|
|
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: str) -> "HttpSignatureDetails":
|
|
bits = {}
|
|
for item in signature.split(","):
|
|
name, value = item.split("=", 1)
|
|
value = value.strip('"')
|
|
bits[name.lower()] = value
|
|
signature_details: HttpSignatureDetails = {
|
|
"headers": bits["headers"].split(),
|
|
"signature": base64.b64decode(bits["signature"]),
|
|
"algorithm": bits["algorithm"],
|
|
"keyid": bits["keyid"],
|
|
}
|
|
return signature_details
|
|
|
|
@classmethod
|
|
def compile_signature(cls, details: "HttpSignatureDetails") -> str:
|
|
value = f'keyId="{details["keyid"]}",headers="'
|
|
value += " ".join(h.lower() for h in details["headers"])
|
|
value += '",signature="'
|
|
value += base64.b64encode(details["signature"]).decode("ascii")
|
|
value += f'",algorithm="{details["algorithm"]}"'
|
|
return value
|
|
|
|
@classmethod
|
|
def verify_signature(
|
|
cls,
|
|
signature: bytes,
|
|
cleartext: str,
|
|
public_key: str,
|
|
):
|
|
x509 = crypto.X509()
|
|
x509.set_pubkey(
|
|
crypto.load_publickey(
|
|
crypto.FILETYPE_PEM,
|
|
public_key.encode("ascii"),
|
|
)
|
|
)
|
|
try:
|
|
crypto.verify(x509, signature, cleartext.encode("ascii"), "sha256")
|
|
except crypto.Error:
|
|
raise VerificationError("Signature mismatch")
|
|
|
|
@classmethod
|
|
def verify_request(cls, request, public_key, skip_date=False):
|
|
"""
|
|
Verifies that the request has a valid signature for its body
|
|
"""
|
|
# Verify body digest
|
|
if "HTTP_DIGEST" in request.META:
|
|
expected_digest = HttpSignature.calculate_digest(request.body)
|
|
if request.META["HTTP_DIGEST"] != expected_digest:
|
|
print("Wrong digest")
|
|
raise VerificationFormatError("Digest is incorrect")
|
|
# Verify date header
|
|
if "HTTP_DATE" in request.META and not skip_date:
|
|
header_date = parse_http_date(request.META["HTTP_DATE"])
|
|
if abs(timezone.now().timestamp() - header_date) > 60:
|
|
print(
|
|
f"Date mismatch - they sent {header_date}, now is {timezone.now().timestamp()}"
|
|
)
|
|
raise VerificationFormatError("Date is too far away")
|
|
# Get the signature details
|
|
if "HTTP_SIGNATURE" not in request.META:
|
|
raise VerificationFormatError("No signature header present")
|
|
signature_details = cls.parse_signature(request.META["HTTP_SIGNATURE"])
|
|
# Reject unknown algorithms
|
|
if signature_details["algorithm"] != "rsa-sha256":
|
|
raise VerificationFormatError("Unknown signature algorithm")
|
|
# Create the signature payload
|
|
headers_string = cls.headers_from_request(request, signature_details["headers"])
|
|
cls.verify_signature(
|
|
signature_details["signature"],
|
|
headers_string,
|
|
public_key,
|
|
)
|
|
|
|
@classmethod
|
|
async def signed_request(
|
|
self,
|
|
uri: str,
|
|
body: Dict,
|
|
private_key: str,
|
|
key_id: str,
|
|
content_type: str = "application/json",
|
|
method: Literal["post"] = "post",
|
|
):
|
|
"""
|
|
Performs an async request to the given path, with a document, signed
|
|
as an identity.
|
|
"""
|
|
uri_parts = urlparse(uri)
|
|
date_string = http_date()
|
|
body_bytes = json.dumps(body).encode("utf8")
|
|
headers = {
|
|
"(request-target)": f"{method} {uri_parts.path}",
|
|
"Host": uri_parts.hostname,
|
|
"Date": date_string,
|
|
"Digest": self.calculate_digest(body_bytes),
|
|
"Content-Type": content_type,
|
|
}
|
|
signed_string = "\n".join(
|
|
f"{name.lower()}: {value}" for name, value in headers.items()
|
|
)
|
|
pkey = crypto.load_privatekey(
|
|
crypto.FILETYPE_PEM,
|
|
private_key.encode("ascii"),
|
|
)
|
|
signature = crypto.sign(
|
|
pkey,
|
|
signed_string.encode("ascii"),
|
|
"sha256",
|
|
)
|
|
headers["Signature"] = self.compile_signature(
|
|
{
|
|
"keyid": key_id,
|
|
"headers": list(headers.keys()),
|
|
"signature": signature,
|
|
"algorithm": "rsa-sha256",
|
|
}
|
|
)
|
|
del headers["(request-target)"]
|
|
async with httpx.AsyncClient() as client:
|
|
print(f"Calling {method} {uri}")
|
|
response = await client.request(
|
|
method,
|
|
uri,
|
|
headers=headers,
|
|
content=body_bytes,
|
|
)
|
|
if response.status_code >= 400:
|
|
raise ValueError(
|
|
f"Request error: {response.status_code} {response.content}"
|
|
)
|
|
return response
|
|
|
|
|
|
class HttpSignatureDetails(TypedDict):
|
|
algorithm: str
|
|
headers: List[str]
|
|
signature: bytes
|
|
keyid: str
|
|
|
|
|
|
class LDSignature:
|
|
"""
|
|
Creates and verifies signatures of JSON-LD documents
|
|
"""
|
|
|
|
@classmethod
|
|
def verify_signature(cls, document: Dict, public_key: str) -> None:
|
|
"""
|
|
Verifies a document
|
|
"""
|
|
try:
|
|
# Strip out the signature from the incoming document
|
|
signature = document.pop("signature")
|
|
# Create the options document
|
|
options = {
|
|
"@context": "https://w3id.org/identity/v1",
|
|
"creator": signature["creator"],
|
|
"created": signature["created"],
|
|
}
|
|
except KeyError:
|
|
raise VerificationFormatError("Invalid signature section")
|
|
if signature["type"].lower() != "rsasignature2017":
|
|
raise VerificationFormatError("Unknown signature type")
|
|
# Get the normalised hash of each document
|
|
final_hash = cls.normalized_hash(options) + cls.normalized_hash(document)
|
|
# Verify the signature
|
|
x509 = crypto.X509()
|
|
x509.set_pubkey(
|
|
crypto.load_publickey(
|
|
crypto.FILETYPE_PEM,
|
|
public_key.encode("ascii"),
|
|
)
|
|
)
|
|
try:
|
|
crypto.verify(
|
|
x509,
|
|
base64.b64decode(signature["signatureValue"]),
|
|
final_hash,
|
|
"sha256",
|
|
)
|
|
except crypto.Error:
|
|
raise VerificationError("Signature mismatch")
|
|
|
|
@classmethod
|
|
def create_signature(
|
|
cls, document: Dict, private_key: str, key_id: str
|
|
) -> Dict[str, str]:
|
|
"""
|
|
Creates the signature for a document
|
|
"""
|
|
# Create the options document
|
|
options: Dict[str, str] = {
|
|
"@context": "https://w3id.org/identity/v1",
|
|
"creator": key_id,
|
|
"created": format_date(timezone.now()),
|
|
}
|
|
# Get the normalised hash of each document
|
|
final_hash = cls.normalized_hash(options) + cls.normalized_hash(document)
|
|
# Create the signature
|
|
pkey = crypto.load_privatekey(
|
|
crypto.FILETYPE_PEM,
|
|
private_key.encode("ascii"),
|
|
)
|
|
signature = base64.b64encode(crypto.sign(pkey, final_hash, "sha256"))
|
|
# Add it to the options document along with other bits
|
|
options["signatureValue"] = signature.decode("ascii")
|
|
options["type"] = "RsaSignature2017"
|
|
return options
|
|
|
|
@classmethod
|
|
def normalized_hash(cls, document) -> bytes:
|
|
"""
|
|
Takes a JSON-LD document and create a hash of its URDNA2015 form,
|
|
in the same way that Mastodon does internally.
|
|
|
|
Reference: https://socialhub.activitypub.rocks/t/making-sense-of-rsasignature2017/347
|
|
"""
|
|
norm_form = jsonld.normalize(
|
|
document,
|
|
{"algorithm": "URDNA2015", "format": "application/n-quads"},
|
|
)
|
|
digest = hashes.Hash(hashes.SHA256())
|
|
digest.update(norm_form.encode("utf8"))
|
|
return digest.finalize().hex().encode("ascii")
|