Present expiration information about previous certificates in TOFU warning messages.
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av98.py
20
av98.py
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@ -706,9 +706,11 @@ Slow internet connection? Use 'set timeout' to be more patient.""")
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# If so, check for a match
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if cached_certs:
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max_count = 0
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most_frequent_cert = None
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for cached_fingerprint, first, last, count in cached_certs:
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if count > max_count:
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max_count = count
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most_frequent_cert = cached_fingerprint
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if fingerprint == cached_fingerprint:
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# Matched!
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self._debug("TOFU: Accepting previously seen ({} times) certificate {}".format(count, fingerprint))
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@ -719,12 +721,27 @@ Slow internet connection? Use 'set timeout' to be more patient.""")
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self.db_conn.commit()
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break
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else:
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if _HAS_CRYPTOGRAPHY:
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# Load the most frequently seen certificate to see if it has
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# expired
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certdir = os.path.join(self.config_dir, "cert_cache")
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with open(os.path.join(certdir, most_frequent_cert+".crt"), "rb") as fp:
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previous_cert = fp.read()
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previous_cert = x509.load_der_x509_certificate(previous_cert, _BACKEND)
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previous_ttl = previous_cert.not_valid_after - now
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print(previous_ttl)
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self._debug("TOFU: Unrecognised certificate {}! Raising the alarm...".format(fingerprint))
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print("****************************************")
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print("[SECURITY WARNING] Unrecognised certificate!")
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print("The certificate presented for {} ({}) has never been seen before.".format(host, address))
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print("A different certificate has previously been seen {} times.".format(max_count))
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print("This MIGHT be a Man-in-the-Middle attack.")
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print("A different certificate has previously been seen {} times.".format(max_count))
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if _HAS_CRYPTOGRAPHY:
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if previous_ttl < datetime.timedelta():
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print("That certificate has expired, which reduces suspicion somewhat.")
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else:
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print("That certificate is still valid for: {}".format(previous_ttl))
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print("****************************************")
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print("Attempt to verify the new certificate fingerprint out-of-band:")
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print(fingerprint)
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@ -734,7 +751,6 @@ Slow internet connection? Use 'set timeout' to be more patient.""")
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VALUES (?, ?, ?, ?, ?, ?)""",
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(host, address, fingerprint, now, now, 1))
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self.db_conn.commit()
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certdir = os.path.join(self.config_dir, "cert_cache")
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with open(os.path.join(certdir, fingerprint+".crt"), "wb") as fp:
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fp.write(cert)
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else:
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