mirror of https://gitlab.com/bashrc2/epicyon
266 lines
10 KiB
Python
266 lines
10 KiB
Python
__filename__ = "posts.py"
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__author__ = "Bob Mottram"
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__credits__ = ['lamia']
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__license__ = "AGPL3+"
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__version__ = "1.2.0"
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__maintainer__ = "Bob Mottram"
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__email__ = "bob@freedombone.net"
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__status__ = "Production"
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# see https://tools.ietf.org/html/draft-cavage-http-signatures-06
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives.serialization import load_pem_private_key
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from cryptography.hazmat.primitives.serialization import load_pem_public_key
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from cryptography.hazmat.primitives.asymmetric import padding
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from cryptography.hazmat.primitives import hashes
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import base64
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from time import gmtime, strftime
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import datetime
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from utils import getFullDomain
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def _getSHA256(msg: str):
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digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
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digest.update(msg)
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return digest.finalize()
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def messageContentDigest(messageBodyJsonStr: str) -> str:
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msg = messageBodyJsonStr.encode('utf-8')
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return base64.b64encode(_getSHA256(msg)).decode('utf-8')
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def signPostHeaders(dateStr: str, privateKeyPem: str,
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nickname: str,
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domain: str, port: int,
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toDomain: str, toPort: int,
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path: str,
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httpPrefix: str,
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messageBodyJsonStr: str) -> str:
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"""Returns a raw signature string that can be plugged into a header and
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used to verify the authenticity of an HTTP transmission.
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"""
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domain = getFullDomain(domain, port)
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toDomain = getFullDomain(toDomain, toPort)
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if not dateStr:
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dateStr = strftime("%a, %d %b %Y %H:%M:%S %Z", gmtime())
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keyID = httpPrefix + '://' + domain + '/users/' + nickname + '#main-key'
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if not messageBodyJsonStr:
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headers = {
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'(request-target)': f'post {path}',
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'host': toDomain,
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'date': dateStr,
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'content-type': 'application/json'
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}
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else:
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bodyDigest = messageContentDigest(messageBodyJsonStr)
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contentLength = len(messageBodyJsonStr)
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headers = {
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'(request-target)': f'post {path}',
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'host': toDomain,
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'date': dateStr,
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'digest': f'SHA-256={bodyDigest}',
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'content-type': 'application/activity+json',
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'content-length': str(contentLength)
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}
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key = load_pem_private_key(privateKeyPem.encode('utf-8'),
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None, backend=default_backend())
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# headers.update({
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# '(request-target)': f'post {path}',
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# })
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# build a digest for signing
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signedHeaderKeys = headers.keys()
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signedHeaderText = ''
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for headerKey in signedHeaderKeys:
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signedHeaderText += f'{headerKey}: {headers[headerKey]}\n'
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signedHeaderText = signedHeaderText.strip()
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headerDigest = _getSHA256(signedHeaderText.encode('ascii'))
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# Sign the digest
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rawSignature = key.sign(headerDigest,
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padding.PKCS1v15(), hashes.SHA256())
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signature = base64.b64encode(rawSignature).decode('ascii')
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# Put it into a valid HTTP signature format
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signatureDict = {
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'keyId': keyID,
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'algorithm': 'rsa-sha256',
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'headers': ' '.join(signedHeaderKeys),
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'signature': signature
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}
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signatureHeader = ','.join(
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[f'{k}="{v}"' for k, v in signatureDict.items()])
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return signatureHeader
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def createSignedHeader(privateKeyPem: str, nickname: str,
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domain: str, port: int,
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toDomain: str, toPort: int,
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path: str, httpPrefix: str, withDigest: bool,
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messageBodyJsonStr: str) -> {}:
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"""Note that the domain is the destination, not the sender
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"""
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contentType = 'application/activity+json'
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headerDomain = getFullDomain(toDomain, toPort)
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dateStr = strftime("%a, %d %b %Y %H:%M:%S %Z", gmtime())
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if not withDigest:
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headers = {
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'(request-target)': f'post {path}',
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'host': headerDomain,
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'date': dateStr
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}
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signatureHeader = \
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signPostHeaders(dateStr, privateKeyPem, nickname,
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domain, port, toDomain, toPort,
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path, httpPrefix, None)
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else:
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bodyDigest = messageContentDigest(messageBodyJsonStr)
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contentLength = len(messageBodyJsonStr)
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headers = {
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'(request-target)': f'post {path}',
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'host': headerDomain,
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'date': dateStr,
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'digest': f'SHA-256={bodyDigest}',
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'content-length': str(contentLength),
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'content-type': contentType
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}
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signatureHeader = \
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signPostHeaders(dateStr, privateKeyPem, nickname,
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domain, port,
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toDomain, toPort,
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path, httpPrefix, messageBodyJsonStr)
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headers['signature'] = signatureHeader
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return headers
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def _verifyRecentSignature(signedDateStr: str) -> bool:
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"""Checks whether the given time taken from the header is within
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12 hours of the current time
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"""
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currDate = datetime.datetime.utcnow()
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dateFormat = "%a, %d %b %Y %H:%M:%S %Z"
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signedDate = datetime.datetime.strptime(signedDateStr, dateFormat)
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timeDiffSec = (currDate - signedDate).seconds
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# 12 hours tollerance
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if timeDiffSec > 43200:
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print('WARN: Header signed too long ago: ' + signedDateStr)
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print(str(timeDiffSec / (60 * 60)) + ' hours')
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return False
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if timeDiffSec < 0:
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print('WARN: Header signed in the future! ' + signedDateStr)
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print(str(timeDiffSec / (60 * 60)) + ' hours')
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return False
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return True
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def verifyPostHeaders(httpPrefix: str, publicKeyPem: str, headers: dict,
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path: str, GETmethod: bool,
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messageBodyDigest: str,
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messageBodyJsonStr: str, debug: bool) -> bool:
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"""Returns true or false depending on if the key that we plugged in here
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validates against the headers, method, and path.
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publicKeyPem - the public key from an rsa key pair
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headers - should be a dictionary of request headers
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path - the relative url that was requested from this site
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GETmethod - GET or POST
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messageBodyJsonStr - the received request body (used for digest)
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"""
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if GETmethod:
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method = 'GET'
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else:
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method = 'POST'
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if debug:
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print('DEBUG: verifyPostHeaders ' + method)
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pubkey = load_pem_public_key(publicKeyPem.encode('utf-8'),
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backend=default_backend())
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# Build a dictionary of the signature values
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signatureHeader = headers['signature']
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signatureDict = {
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k: v[1:-1]
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for k, v in [i.split('=', 1) for i in signatureHeader.split(',')]
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}
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# Unpack the signed headers and set values based on current headers and
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# body (if a digest was included)
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signedHeaderList = []
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for signedHeader in signatureDict['headers'].split(' '):
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if debug:
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print('DEBUG: verifyPostHeaders signedHeader=' + signedHeader)
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if signedHeader == '(request-target)':
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appendStr = f'(request-target): {method.lower()} {path}'
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signedHeaderList.append(appendStr)
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elif signedHeader == 'digest':
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if messageBodyDigest:
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bodyDigest = messageBodyDigest
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else:
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bodyDigest = messageContentDigest(messageBodyJsonStr)
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signedHeaderList.append(f'digest: SHA-256={bodyDigest}')
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elif signedHeader == 'content-length':
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if headers.get(signedHeader):
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appendStr = f'content-length: {headers[signedHeader]}'
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signedHeaderList.append(appendStr)
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else:
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if headers.get('Content-Length'):
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contentLength = headers['Content-Length']
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signedHeaderList.append(f'content-length: {contentLength}')
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else:
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if headers.get('Content-length'):
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contentLength = headers['Content-length']
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appendStr = f'content-length: {contentLength}'
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signedHeaderList.append(appendStr)
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else:
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if debug:
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print('DEBUG: verifyPostHeaders ' + signedHeader +
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' not found in ' + str(headers))
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else:
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if headers.get(signedHeader):
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if signedHeader == 'date':
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if not _verifyRecentSignature(headers[signedHeader]):
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if debug:
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print('DEBUG: ' +
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'verifyPostHeaders date is not recent ' +
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headers[signedHeader])
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return False
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signedHeaderList.append(
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f'{signedHeader}: {headers[signedHeader]}')
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else:
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signedHeaderCap = signedHeader.capitalize()
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if signedHeaderCap == 'Date':
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if not _verifyRecentSignature(headers[signedHeaderCap]):
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if debug:
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print('DEBUG: ' +
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'verifyPostHeaders date is not recent ' +
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headers[signedHeader])
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return False
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if headers.get(signedHeaderCap):
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signedHeaderList.append(
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f'{signedHeader}: {headers[signedHeaderCap]}')
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if debug:
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print('DEBUG: signedHeaderList: ' + str(signedHeaderList))
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# Now we have our header data digest
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signedHeaderText = '\n'.join(signedHeaderList)
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headerDigest = _getSHA256(signedHeaderText.encode('ascii'))
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# Get the signature, verify with public key, return result
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signature = base64.b64decode(signatureDict['signature'])
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try:
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pubkey.verify(
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signature,
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headerDigest,
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padding.PKCS1v15(),
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hashes.SHA256())
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return True
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except BaseException:
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if debug:
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print('DEBUG: verifyPostHeaders pkcs1_15 verify failure')
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return False
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