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epicyon/httpsig.py

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Python
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__filename__ = "posts.py"
__author__ = "Bob Mottram"
__credits__ = ['lamia']
__license__ = "AGPL3+"
__version__ = "0.0.1"
__maintainer__ = "Bob Mottram"
__email__ = "bob@freedombone.net"
__status__ = "Production"
# see https://tools.ietf.org/html/draft-cavage-http-signatures-06
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA256
#from Crypto.Signature import PKCS1_v1_5
from Crypto.Signature import pkcs1_15
from requests.auth import AuthBase
import base64
import json
from time import gmtime, strftime
import datetime
from pprint import pprint
def messageContentDigest(messageBodyJsonStr: str) -> str:
return base64.b64encode(SHA256.new(messageBodyJsonStr.encode('utf-8')).digest()).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.
"""
if port:
if port!=80 and port!=443:
if ':' not in domain:
domain=domain+':'+str(port)
if toPort:
if toPort!=80 and toPort!=443:
if ':' not in toDomain:
toDomain=toDomain+':'+str(port)
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)
headers={'(request-target)': f'post {path}','host': toDomain,'date': dateStr,'digest': f'SHA-256={bodyDigest}','content-type': 'application/activity+json'}
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'
#print(f'*********************signing: headerKey: {headerKey}: {headers[headerKey]}')
signedHeaderText = signedHeaderText.strip()
#print('******************************Send: signedHeaderText: '+signedHeaderText)
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=toDomain
if toPort:
if toPort!=80 and toPort!=443:
if ':' not in headerDomain:
headerDomain=headerDomain+':'+str(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)
#print('***************************Send (request-target): post '+path)
#print('***************************Send host: '+headerDomain)
#print('***************************Send date: '+dateStr)
#print('***************************Send digest: '+bodyDigest)
#print('***************************Send Content-type: '+contentType)
#print('***************************Send messageBodyJsonStr: '+messageBodyJsonStr)
headers = {'(request-target)': f'post {path}','host': headerDomain,'date': dateStr,'digest': f'SHA-256={bodyDigest}','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()
signedDate=datetime.datetime.strptime(signedDateStr,"%a, %d %b %Y %H:%M:%S %Z")
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) -> 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'
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(',')]
}
#print('********************signatureHeader: '+str(signatureHeader))
#print('********************signatureDict: '+str(signatureDict))
# 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 signedHeader == '(request-target)':
signedHeaderList.append(
f'(request-target): {method.lower()} {path}')
#print('***************************Verify (request-target): '+method.lower()+' '+path)
elif signedHeader == 'digest':
if messageBodyDigest:
bodyDigest=messageBodyDigest
else:
bodyDigest = messageContentDigest(messageBodyJsonStr)
signedHeaderList.append(f'digest: SHA-256={bodyDigest}')
#print('***************************Verify digest: SHA-256='+bodyDigest)
#print('***************************Verify messageBodyJsonStr: '+messageBodyJsonStr)
else:
if headers.get(signedHeader):
if signedHeader=='date':
if not verifyRecentSignature(headers[signedHeader]):
return False
#print('***************************Verify '+signedHeader+': '+headers[signedHeader])
signedHeaderList.append(
f'{signedHeader}: {headers[signedHeader]}')
else:
signedHeaderCap=signedHeader.capitalize()
if signedHeaderCap=='Date':
if not verifyRecentSignature(headers[signedHeaderCap]):
return False
#print('***************************Verify '+signedHeaderCap+': '+headers[signedHeaderCap])
if headers.get(signedHeaderCap):
signedHeaderList.append(
f'{signedHeader}: {headers[signedHeaderCap]}')
#print('***********************signedHeaderList: ')
#pprint(signedHeaderList)
# Now we have our header data digest
signedHeaderText = '\n'.join(signedHeaderList)
#print('***********************Verify: signedHeaderText: '+signedHeaderText)
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):
return False
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