epicyon/httpsig.py

400 lines
16 KiB
Python

__filename__ = "httpsig.py"
__author__ = "Bob Mottram"
__credits__ = ['lamia']
__license__ = "AGPL3+"
__version__ = "1.2.0"
__maintainer__ = "Bob Mottram"
__email__ = "bob@freedombone.net"
__status__ = "Production"
# see https://tools.ietf.org/html/draft-cavage-http-signatures-06
#
# This might change in future
# see https://tools.ietf.org/html/draft-ietf-httpbis-message-signatures-01
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.serialization import load_pem_private_key
from cryptography.hazmat.primitives.serialization import load_pem_public_key
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import utils as hazutils
import calendar
import base64
from time import gmtime, strftime
import datetime
from utils import getFullDomain
from utils import getSHA256
def messageContentDigest(messageBodyJsonStr: str) -> str:
msg = messageBodyJsonStr.encode('utf-8')
hashResult = getSHA256(msg)
return base64.b64encode(hashResult).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)
}
key = load_pem_private_key(privateKeyPem.encode('utf-8'),
None, backend=default_backend())
# 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()
# signedHeaderText.encode('ascii') matches
headerDigest = getSHA256(signedHeaderText.encode('ascii'))
# print('headerDigest2: ' + str(headerDigest))
# Sign the digest
rawSignature = key.sign(headerDigest,
padding.PKCS1v15(),
hazutils.Prehashed(hashes.SHA256()))
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 signPostHeadersNew(dateStr: str, privateKeyPem: str,
nickname: str,
domain: str, port: int,
toDomain: str, toPort: int,
path: str,
httpPrefix: str,
messageBodyJsonStr: str,
algorithm: str) -> (str, str):
"""Returns a raw signature strings that can be plugged into a header
as "Signature-Input" and "Signature"
used to verify the authenticity of an HTTP transmission.
See https://tools.ietf.org/html/draft-ietf-httpbis-message-signatures-01
"""
domain = getFullDomain(domain, port)
toDomain = getFullDomain(toDomain, toPort)
timeFormat = "%a, %d %b %Y %H:%M:%S %Z"
if not dateStr:
currTime = gmtime()
secondsSinceEpoch = int(calendar.timegm(currTime))
dateStr = strftime(timeFormat, currTime)
else:
currTime = datetime.datetime.strptime(dateStr, timeFormat)
secondsSinceEpoch = int(currTime.timestamp())
keyID = httpPrefix + '://' + domain + '/users/' + nickname + '#main-key'
if not messageBodyJsonStr:
headers = {
'*request-target': f'post {path}',
'*created': str(secondsSinceEpoch),
'host': toDomain,
'date': dateStr,
'content-type': 'application/json'
}
else:
bodyDigest = messageContentDigest(messageBodyJsonStr)
contentLength = len(messageBodyJsonStr)
headers = {
'*request-target': f'post {path}',
'*created': str(secondsSinceEpoch),
'host': toDomain,
'date': dateStr,
'digest': f'SHA-256={bodyDigest}',
'content-type': 'application/activity+json',
'content-length': str(contentLength)
}
key = load_pem_private_key(privateKeyPem.encode('utf-8'),
None, backend=default_backend())
# build a digest for signing
signedHeaderKeys = headers.keys()
signedHeaderText = ''
for headerKey in signedHeaderKeys:
signedHeaderText += f'{headerKey}: {headers[headerKey]}\n'
signedHeaderText = signedHeaderText.strip()
headerDigest = getSHA256(signedHeaderText.encode('ascii'))
# Sign the digest. Potentially other signing algorithms can be added here.
signature = ''
if algorithm == 'rsa-sha256':
rawSignature = key.sign(headerDigest,
padding.PKCS1v15(),
hazutils.Prehashed(hashes.SHA256()))
signature = base64.b64encode(rawSignature).decode('ascii')
sigKey = 'sig1'
# Put it into a valid HTTP signature format
signatureInputDict = {
'keyId': keyID,
}
signatureIndexHeader = '; '.join(
[f'{k}="{v}"' for k, v in signatureInputDict.items()])
signatureIndexHeader += '; alg=hs2019'
signatureIndexHeader += '; created=' + str(secondsSinceEpoch)
signatureIndexHeader += \
'; ' + sigKey + '=(' + ', '.join(signedHeaderKeys) + ')'
signatureDict = {
sigKey: signature
}
signatureHeader = '; '.join(
[f'{k}=:{v}:' for k, v in signatureDict.items()])
return signatureIndexHeader, 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,
noRecencyCheck=False) -> 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)
pubkey = load_pem_public_key(publicKeyPem.encode('utf-8'),
backend=default_backend())
# Build a dictionary of the signature values
if headers.get('Signature-Input'):
signatureHeader = headers['Signature-Input']
fieldSep2 = ','
# split the signature input into separate fields
signatureDict = {
k.strip(): v.strip()
for k, v in [i.split('=', 1) for i in signatureHeader.split(';')]
}
requestTargetKey = None
requestTargetStr = None
for k, v in signatureDict.items():
if v.startswith('('):
requestTargetKey = k
requestTargetStr = v[1:-1]
break
if not requestTargetKey:
return False
signatureDict[requestTargetKey] = requestTargetStr
else:
requestTargetKey = 'headers'
signatureHeader = headers['signature']
fieldSep2 = ' '
# split the signature input into separate fields
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[requestTargetKey].split(fieldSep2):
signedHeader = signedHeader.strip()
if debug:
print('DEBUG: verifyPostHeaders signedHeader=' + signedHeader)
if signedHeader == '(request-target)':
# original Mastodon http signature
appendStr = f'(request-target): {method.lower()} {path}'
signedHeaderList.append(appendStr)
elif '*request-target' in signedHeader:
# https://tools.ietf.org/html/
# draft-ietf-httpbis-message-signatures-01
appendStr = f'*request-target: {method.lower()} {path}'
# remove ()
# if appendStr.startswith('('):
# appendStr = appendStr.split('(')[1]
# if ')' in appendStr:
# appendStr = appendStr.split(')')[0]
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' and not noRecencyCheck:
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 = getSHA256(signedHeaderText.encode('ascii'))
# Get the signature, verify with public key, return result
signature = None
if headers.get('Signature-Input') and headers.get('Signature'):
# https://tools.ietf.org/html/
# draft-ietf-httpbis-message-signatures-01
headersSig = headers['Signature']
# remove sig1=:
if requestTargetKey + '=:' in headersSig:
headersSig = headersSig.split(requestTargetKey + '=:')[1]
headersSig = headersSig[:len(headersSig)-1]
signature = base64.b64decode(headersSig)
else:
# Original Mastodon signature
signature = base64.b64decode(signatureDict['signature'])
try:
pubkey.verify(
signature,
headerDigest,
padding.PKCS1v15(),
hazutils.Prehashed(hashes.SHA256()))
return True
except BaseException:
if debug:
print('DEBUG: verifyPostHeaders pkcs1_15 verify failure')
return False