epicyon/httpsig.py

259 lines
9.7 KiB
Python

__filename__ = "posts.py"
__author__ = "Bob Mottram"
__credits__ = ['lamia']
__license__ = "AGPL3+"
__version__ = "1.1.0"
__maintainer__ = "Bob Mottram"
__email__ = "bob@freedombone.net"
__status__ = "Production"
# see https://tools.ietf.org/html/draft-cavage-http-signatures-06
try:
from Cryptodome.PublicKey import RSA
from Cryptodome.Hash import SHA256
from Cryptodome.Signature import pkcs1_15
except ImportError:
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA256
# from Crypto.Signature import PKCS1_v1_5
from Crypto.Signature import pkcs1_15
import base64
from time import gmtime, strftime
import datetime
from utils import getFullDomain
def messageContentDigest(messageBodyJsonStr: str) -> str:
msg = messageBodyJsonStr.encode('utf-8')
digestStr = SHA256.new(msg).digest()
return base64.b64encode(digestStr).decode('utf-8')
def signPostHeaders(dateStr: str, privateKeyPem: str,
nickname: str,
domain: str, port: int,
toDomain: str, toPort: int,
path: str,
httpPrefix: str,
messageBodyJsonStr: str) -> str:
"""Returns a raw signature string that can be plugged into a header and
used to verify the authenticity of an HTTP transmission.
"""
domain = getFullDomain(domain, port)
toDomain = getFullDomain(toDomain, toPort)
if not dateStr:
dateStr = strftime("%a, %d %b %Y %H:%M:%S %Z", gmtime())
keyID = httpPrefix + '://' + domain + '/users/' + nickname + '#main-key'
if not messageBodyJsonStr:
headers = {
'(request-target)': f'post {path}',
'host': toDomain,
'date': dateStr,
'content-type': 'application/json'
}
else:
bodyDigest = messageContentDigest(messageBodyJsonStr)
contentLength = len(messageBodyJsonStr)
headers = {
'(request-target)': f'post {path}',
'host': toDomain,
'date': dateStr,
'digest': f'SHA-256={bodyDigest}',
'content-type': 'application/activity+json',
'content-length': str(contentLength)
}
privateKeyPem = RSA.import_key(privateKeyPem)
# headers.update({
# '(request-target)': f'post {path}',
# })
# build a digest for signing
signedHeaderKeys = headers.keys()
signedHeaderText = ''
for headerKey in signedHeaderKeys:
signedHeaderText += f'{headerKey}: {headers[headerKey]}\n'
signedHeaderText = signedHeaderText.strip()
headerDigest = SHA256.new(signedHeaderText.encode('ascii'))
# Sign the digest
rawSignature = pkcs1_15.new(privateKeyPem).sign(headerDigest)
signature = base64.b64encode(rawSignature).decode('ascii')
# Put it into a valid HTTP signature format
signatureDict = {
'keyId': keyID,
'algorithm': 'rsa-sha256',
'headers': ' '.join(signedHeaderKeys),
'signature': signature
}
signatureHeader = ','.join(
[f'{k}="{v}"' for k, v in signatureDict.items()])
return signatureHeader
def createSignedHeader(privateKeyPem: str, nickname: str,
domain: str, port: int,
toDomain: str, toPort: int,
path: str, httpPrefix: str, withDigest: bool,
messageBodyJsonStr: str) -> {}:
"""Note that the domain is the destination, not the sender
"""
contentType = 'application/activity+json'
headerDomain = getFullDomain(toDomain, toPort)
dateStr = strftime("%a, %d %b %Y %H:%M:%S %Z", gmtime())
if not withDigest:
headers = {
'(request-target)': f'post {path}',
'host': headerDomain,
'date': dateStr
}
signatureHeader = \
signPostHeaders(dateStr, privateKeyPem, nickname,
domain, port, toDomain, toPort,
path, httpPrefix, None)
else:
bodyDigest = messageContentDigest(messageBodyJsonStr)
contentLength = len(messageBodyJsonStr)
headers = {
'(request-target)': f'post {path}',
'host': headerDomain,
'date': dateStr,
'digest': f'SHA-256={bodyDigest}',
'content-length': str(contentLength),
'content-type': contentType
}
signatureHeader = \
signPostHeaders(dateStr, privateKeyPem, nickname,
domain, port,
toDomain, toPort,
path, httpPrefix, messageBodyJsonStr)
headers['signature'] = signatureHeader
return headers
def _verifyRecentSignature(signedDateStr: str) -> bool:
"""Checks whether the given time taken from the header is within
12 hours of the current time
"""
currDate = datetime.datetime.utcnow()
dateFormat = "%a, %d %b %Y %H:%M:%S %Z"
signedDate = datetime.datetime.strptime(signedDateStr, dateFormat)
timeDiffSec = (currDate - signedDate).seconds
# 12 hours tollerance
if timeDiffSec > 43200:
print('WARN: Header signed too long ago: ' + signedDateStr)
print(str(timeDiffSec / (60 * 60)) + ' hours')
return False
if timeDiffSec < 0:
print('WARN: Header signed in the future! ' + signedDateStr)
print(str(timeDiffSec / (60 * 60)) + ' hours')
return False
return True
def verifyPostHeaders(httpPrefix: str, publicKeyPem: str, headers: dict,
path: str, GETmethod: bool,
messageBodyDigest: str,
messageBodyJsonStr: str, debug: bool) -> bool:
"""Returns true or false depending on if the key that we plugged in here
validates against the headers, method, and path.
publicKeyPem - the public key from an rsa key pair
headers - should be a dictionary of request headers
path - the relative url that was requested from this site
GETmethod - GET or POST
messageBodyJsonStr - the received request body (used for digest)
"""
if GETmethod:
method = 'GET'
else:
method = 'POST'
if debug:
print('DEBUG: verifyPostHeaders ' + method)
publicKeyPem = RSA.import_key(publicKeyPem)
# Build a dictionary of the signature values
signatureHeader = headers['signature']
signatureDict = {
k: v[1:-1]
for k, v in [i.split('=', 1) for i in signatureHeader.split(',')]
}
# Unpack the signed headers and set values based on current headers and
# body (if a digest was included)
signedHeaderList = []
for signedHeader in signatureDict['headers'].split(' '):
if debug:
print('DEBUG: verifyPostHeaders signedHeader=' + signedHeader)
if signedHeader == '(request-target)':
appendStr = f'(request-target): {method.lower()} {path}'
signedHeaderList.append(appendStr)
elif signedHeader == 'digest':
if messageBodyDigest:
bodyDigest = messageBodyDigest
else:
bodyDigest = messageContentDigest(messageBodyJsonStr)
signedHeaderList.append(f'digest: SHA-256={bodyDigest}')
elif signedHeader == 'content-length':
if headers.get(signedHeader):
appendStr = f'content-length: {headers[signedHeader]}'
signedHeaderList.append(appendStr)
else:
if headers.get('Content-Length'):
contentLength = headers['Content-Length']
signedHeaderList.append(f'content-length: {contentLength}')
else:
if headers.get('Content-length'):
contentLength = headers['Content-length']
appendStr = f'content-length: {contentLength}'
signedHeaderList.append(appendStr)
else:
if debug:
print('DEBUG: verifyPostHeaders ' + signedHeader +
' not found in ' + str(headers))
else:
if headers.get(signedHeader):
if signedHeader == 'date':
if not _verifyRecentSignature(headers[signedHeader]):
if debug:
print('DEBUG: ' +
'verifyPostHeaders date is not recent ' +
headers[signedHeader])
return False
signedHeaderList.append(
f'{signedHeader}: {headers[signedHeader]}')
else:
signedHeaderCap = signedHeader.capitalize()
if signedHeaderCap == 'Date':
if not _verifyRecentSignature(headers[signedHeaderCap]):
if debug:
print('DEBUG: ' +
'verifyPostHeaders date is not recent ' +
headers[signedHeader])
return False
if headers.get(signedHeaderCap):
signedHeaderList.append(
f'{signedHeader}: {headers[signedHeaderCap]}')
if debug:
print('DEBUG: signedHeaderList: ' + str(signedHeaderList))
# Now we have our header data digest
signedHeaderText = '\n'.join(signedHeaderList)
headerDigest = SHA256.new(signedHeaderText.encode('ascii'))
# Get the signature, verify with public key, return result
signature = base64.b64decode(signatureDict['signature'])
try:
pkcs1_15.new(publicKeyPem).verify(headerDigest, signature)
return True
except (ValueError, TypeError):
if debug:
print('DEBUG: verifyPostHeaders pkcs1_15 verify failure')
return False