__filename__ = "posts.py" __author__ = "Bob Mottram" __credits__ = ['lamia'] __license__ = "AGPL3+" __version__ = "1.0.0" __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; charset=utf-8'} else: bodyDigest=messageContentDigest(messageBodyJsonStr) headers={'(request-target)': f'post {path}','host': toDomain,'date': dateStr,'digest': f'SHA-256={bodyDigest}','content-type': 'application/activity+json; charset=utf-8'} 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; charset=utf-8' 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