#!/usr/bin/python
# -*- coding: utf-8 -*-     

import time
import datetime
import base64
import argparse
import errno
from certtools import *

NAGIOS_OK = 0
NAGIOS_WARN = 1
NAGIOS_CRIT = 2
NAGIOS_UNKNOWN = 3

parser = argparse.ArgumentParser(description="")
parser.add_argument('--audit', action='store_true', help="run lightweight auditor verifying consistency in STH")
parser.add_argument('--build-sth', action='store_true', help="get all entries and construct STH")
parser.add_argument('--baseurl', required=True, help="Base URL for CT log")
parser.add_argument('--sthfile',
                    required=True,
                    metavar='file',
                    help="File containing current STH")
parser.add_argument('--keyfile',
                    metavar='file',
                    required=True,
                    help="File containing current STH")

class UTC(datetime.tzinfo):
    def utcoffset(self, dt):
      return datetime.timedelta(hours=0)
    def dst(self, dt):
        return datetime.timedelta(0)

def reduce_layer(layer):
    new_layer = []
    while len(layer) > 1:
        e1 = layer.pop(0)
        e2 = layer.pop(0)
        new_layer.append(internal_hash((e1,e2)))
    return new_layer

def reduce_tree(entries, layers):
    if len(entries) == 0 and layers is []:
        return [[hashlib.sha256().digest()]]
  
    layer_idx = 0
    layers[layer_idx] += entries

    while len(layers[layer_idx]) > 1:
        if len(layers) == layer_idx + 1:
            layers.append([])

        layers[layer_idx + 1] += reduce_layer(layers[layer_idx]) 
        layer_idx += 1
    return layers

def reduce_subtree_to_root(layers):
    while len(layers) > 1:
        if len(layers[1]) == 0:
            layers[1] = layers[0]
        else:
            layers[1] += next_merkle_layer(layers[0])
        del layers[0]

    if len(layers[0]) > 1:
        return next_merkle_layer(layers[0])
    return layers[0]

def get_and_verify_sth(url, key):
    try:
        sth =  get_sth(url)
    except:
        print time.strftime('%H:%M:%S') + " ERROR: Failed to retrieve STH from " + url
        sys.exit(NAGIOS_CRIT)

    # Check signature on the STH
    try:
        check_sth_signature(url, sth, key)
        # write_file("plausible-sth.json", tmp_sth)
    except:
        error_str = time.strftime('%H:%M:%S') + " ERROR: Could not verify signature from " + url
        print error_str
        sys.exit(NAGIOS_CRIT)
    return sth

def fetch_all_sth():
    sths = {}
    for base_url in base_urls:
        # Fetch STH
        try:
            sths[base_url] =  get_sth(base_url)
        except:
            sths[base_url] = None
            error_str = time.strftime('%H:%M:%S') + " ERROR: Failed to retrieve STH from " + base_url
            print error_str
            errors.append(error_str)
            continue

        # Check signature on the STH
        try:
            check_sth_signature(base_url, sths[base_url], logkeys[base_url])
        except:
            error_str = time.strftime('%H:%M:%S') + " ERROR: Could not verify signature from " + base_url
            print error_str
            errors.append(error_str)
            continue

        # Add timing info 
        # try:
        #     if base_url not in timings:
        #         timings[base_url] = {"last":sths[base_url]["timestamp"], "longest":0}
        #     else:
        #         then = datetime.datetime.fromtimestamp(int(timings[base_url]["last"])/1000)
        #         now = datetime.datetime.fromtimestamp(int(sths[base_url]["timestamp"])/1000)
        #         tdelta = now - then

        #         timings[base_url]["last"] = sths[base_url]["timestamp"]

        #         if tdelta.total_seconds() > timings[base_url]["longest"]:
        #             timings[base_url]["longest"] = tdelta.total_seconds()

        # except Exception, err:
        #     print Exception, err
        #     print time.strftime('%H:%M:%S') + "ERROR: Failed to set TIME info for STH"

    return sths

def verify_progress(url, old, new):
    if old and new:
        if new["tree_size"] == old["tree_size"]:
            if old["sha256_root_hash"] != new["sha256_root_hash"]:
                print time.strftime('%H:%M:%S') + " CRITICAL: root hash is different for same tree size in " + url
                sys.exit(NAGIOS_CRIT)

        elif new["tree_size"] < old["tree_size"]:
            print time.strftime('%H:%M:%S') + " CRITICAL: new tree smaller than previous tree (%d < %d)" % \
              (new["tree_size"], old["tree_size"])
            sys.exit(NAGIOS_WARN)
    if new:
        age = time.time() - new["timestamp"]/1000
        sth_time = datetime.datetime.fromtimestamp(new['timestamp'] / 1000, UTC()).strftime("%Y-%m-%d %H:%M:%S")
        roothash = new['sha256_root_hash']
        if age > 24 * 3600:
            print time.strftime('%H:%M:%S') + " CRITICAL: %s is older than 24h: %s UTC" % (url, sth_time)
            sys.exit(NAGIOS_CRIT)
        elif age > 12 * 3600:
            print time.strftime('%H:%M:%S') + " WARNING: %s is older than 12h: %s UTC" % (url, sth_time)
            sys.exit(NAGIOS_WARN)
        elif age > 6 * 3600:
            print time.strftime('%H:%M:%S') + " WARNING: %s is older than 6h: %s UTC" % (url, sth_time)
            sys.exit(NAGIOS_WARN)

def verify_consistency(url, old, new):
    if old and new:
        try:
            if old["tree_size"]!= new["tree_size"]:
                consistency_proof = get_consistency_proof(url, old["tree_size"], new["tree_size"])
                decoded_consistency_proof = []
                for item in consistency_proof:
                    decoded_consistency_proof.append(base64.b64decode(item))
                res = verify_consistency_proof(decoded_consistency_proof, old["tree_size"], new["tree_size"], old["sha256_root_hash"])
                
                if old["sha256_root_hash"] != str(base64.b64encode(res[0])):
                    print time.strftime('%H:%M:%S') + " Verification of old hash failed! " + old["sha256_root_hash"] + str(base64.b64encode(res[0]))
                    sys.exit(NAGIOS_CRIT)
                    # errors.append(time.strftime('%H:%M:%S') + " ERROR: Failed to verify consistency for " + url + ", tree size " + old[url]["tree_size"])
                elif new[url]["sha256_root_hash"] != str(base64.b64encode(res[1])):
                    print time.strftime('%H:%M:%S') + " Verification of new hash failed! " + new["sha256_root_hash"] + str(base64.b64encode(res[1]))
                    sys.exit(NAGIOS_CRIT)
                    # errors.append(time.strftime('%H:%M:%S') + " ERROR: Failed to verify consistency for " + url + ", tree size " + new[url]["tree_size"])
                else:
                    print time.strftime("%H:%M:%S") + " New STH from " + url + ", timestamp: " + \
                        str(new["timestamp"]) + ", size: " + str(new["tree_size"]) + "...OK."

        except:
          print time.strftime('%H:%M:%S') + " ERROR: Could not verify consistency for " + url
          sys.exit(NAGIOS_CRIT)

def verify_inclusion_all(url, old, new):
    if old and new:
        try:
            if old["tree_size"]!= new["tree_size"]:
                entries = get_entries(url, old["tree_size"], new["tree_size"] -1)["entries"]
                success = True
                for i in entries:
                    h = get_leaf_hash(base64.b64decode(i["leaf_input"]))
                    if not verify_inclusion_by_hash(url, h):
                        success = False

                if not success:
                    # print time.strftime("%H:%M:%S") + " Verifying inclusion for " + str(len(entries)) + " new entries in " + url + " ...OK"
                # else:
                    print time.strftime('%H:%M:%S') + " ERROR: Failed to prove inclusion of all new entries in " + url
                    sys.exit(NAGIOS_CRIT)
                    # errors.append(time.strftime('%H:%M:%S') + " ERROR: Failed to prove inclusion of all new entries in " + url)
        except:
            print time.strftime('%H:%M:%S') + " ERROR: Failed to prove inclusion of all new entries in " + url
            # errors.append(time.strftime('%H:%M:%S') + " ERROR: Failed to prove inclusion of all new entries in " + url)
            sys.exit(NAGIOS_CRIT)

def fetch_and_build_tree(old_sth, base_url):
    sth = old_sth[base_url]
    subtree = [[]]
    idx = 0

    res_strings = [""]

    print time.strftime('%H:%M:%S') + " Getting all entries from " + base_url
    while idx < sth["tree_size"]:
        pre_size = idx
        entries = get_entries(base_url, idx, sth["tree_size"]-1)["entries"]
        
        new_leafs = []
        for item in entries:
            new_leafs.append(get_leaf_hash(base64.b64decode(item["leaf_input"])))
        idx += len(new_leafs)
        print time.strftime('%H:%M:%S') + " Got entries " + str(pre_size) + " to " + str(idx) + " from " + base_url
        subtree = reduce_tree(new_leafs, subtree)

    root = base64.b64encode(reduce_subtree_to_root(subtree)[0])

    if root == sth["sha256_root_hash"]:
        print time.strftime('%H:%M:%S') + " Verifying root hashes for " + base_url + "...OK."
        res_strings.append("STH for " + base_url + " built successfully.")
    else:
        print time.strftime('%H:%M:%S') + " ERROR: Failed to verify root hashes! STH root: " + sth["sha256_root_hash"] + ", Tree root: " + root
        res_strings.append(time.strftime('%H:%M:%S') + " " + base_url + " Failed! STH root: " + sth["sha256_root_hash"] + " Calculated root: " + root)
        errors.append(time.strftime('%H:%M:%S') + " ERROR: Failed to verify root hash for " + base_url + ", tre size " + sth["tree_size"])

    for item in res_strings:
        print item + "\n"

def verify_inclusion_by_hash(base_url, leaf_hash):
    try: 
        tmp_sth = get_sth(base_url)
        proof = get_proof_by_hash(base_url, leaf_hash, tmp_sth["tree_size"])

        decoded_inclusion_proof = []
        for item in proof["audit_path"]:
            decoded_inclusion_proof.append(base64.b64decode(item))
        
        root = base64.b64encode(verify_inclusion_proof(decoded_inclusion_proof, proof["leaf_index"], tmp_sth["tree_size"], leaf_hash))

        if tmp_sth["sha256_root_hash"] == root:
            # print "Verifying inclusion for entry " + str(proof["leaf_index"]) + " in " + base_url + "...OK."
            return True
        else:
            print time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(proof["leaf_index"]) + " in " + base_url
            errors.append(time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(proof["leaf_index"]) + " in " + base_url)
            return False
    except:
        print time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for hashed entry in " + base_url
        errors.append(time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for hashed entry in " + base_url)
        return False

def verify_inclusion_by_index(base_url, index):
    try: 
        tmp_sth = get_sth(base_url)
        proof = get_proof_by_index(base_url, index, tmp_sth["tree_size"])

        decoded_inclusion_proof = []
        for item in proof["audit_path"]:
            decoded_inclusion_proof.append(base64.b64decode(item))

        root = base64.b64encode(verify_inclusion_proof(decoded_inclusion_proof, index, tmp_sth["tree_size"], get_leaf_hash(base64.b64decode(proof["leaf_input"]))))

        if tmp_sth["sha256_root_hash"] == root:
            print time.strftime('%H:%M:%S') + " Verifying inclusion for entry " + str(index) + " in " + base_url + "...OK."
        else:
            print time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(index) + " in " + base_url
            errors.append(time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(index) + " in " + base_url)
    except:
        print time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(index) + " in " + base_url
        errors.append(time.strftime('%H:%M:%S') + " ERROR: Could not prove inclusion for entry " + str(index) + " in " + base_url)

def get_proof_by_index(baseurl, index, tree_size):
    try:
        params = urllib.urlencode({"leaf_index":index,
                                   "tree_size":tree_size})
        result = \
          urlopen(baseurl + "ct/v1/get-entry-and-proof?" + params).read()
        return json.loads(result)
    except urllib2.HTTPError, e:
        print "ERROR:", e.read()
        sys.exit(0)

def get_all_roots(base_url):
    # print "Fetching roots from " + base_url
    result = urlopen(base_url + "ct/v1/get-roots").read()
    certs = json.loads(result)["certificates"]
    print time.strftime('%H:%M:%S') + " Received " + str(len(certs)) + " certs from " + base_url

    for accepted_cert in certs:
        subject = get_cert_info(base64.decodestring(accepted_cert))["subject"]
        issuer = get_cert_info(base64.decodestring(accepted_cert))["issuer"]
        if subject == issuer:
            root_cert = base64.decodestring(accepted_cert)
            print get_cert_info(root_cert)["subject"]

def read_sth(fn):
    try:
        f = open(fn)
    except IOError, e:
        if e.errno == errno.ENOENT:
            return None
        raise e
    return json.loads(f.read())

def write_file(fn, sth):
    tempname = fn + ".new"
    open(tempname, 'w').write(json.dumps(sth))
    mv_file(tempname, fn)


def main(args):
    try:
        log_key = get_public_key_from_file(args.keyfile)
    except:
        print time.strftime('%H:%M:%S') + " ERROR: Failed to load keyfile " + args.keyfile
        sys.exit(NAGIOS_WARN)

    old_sth = read_sth(args.sthfile)
    new_sth =  get_and_verify_sth(args.baseurl, log_key)
    write_file(args.sthfile, new_sth)

    verify_progress(args.baseurl, old_sth, new_sth)

    verify_consistency(args.baseurl, old_sth, new_sth)

    verify_inclusion_all(args.baseurl, old_sth, new_sth)

    print "Everything OK from " + args.baseurl 
    sys.exit(NAGIOS_OK)


if __name__ == '__main__':
    main(parser.parse_args())