Slides for my Voxxed LU talk on SSL/TLS.

1. SSL/TLS FOR MORTALS
@mthmuldersmaartenm@infosupport.com

2. WHY BOTHER?
Using SSL/TLS correctly is o en hard to achieve
...and understand!
Crucial for secure connection between systems
Globally deployed (intra-)cloud applications

3. data unit layers
Data
Data
Data
Segments
Packets
Frames
Bits
Application
Network Process to Application
Presentation
Data Representation
and Encryption
Session
Interhost Communication
Transport
End­to­End Connections
and Reliability
Network
Path Determination and
Logical Addressing (IP)
Data Link
Physical Addressing
(MAC and LLC)
Physical
Media, Signal and
Binary Transmission
Host LayersMedia Layers

4. DEMO TIME!
What's the issue?

5. HOW TO PREVENT
THIS?
1. public/private key
encryption
2. signed certificates
3. certificate authorities

6. SSL 1.0
never released
SSL 2.0
1995 - POODLE (2011)
SSL 3.0
1996 - POODLE (2014)
TLS 1.0
1999 - BEAST (2011)
TLS 1.1
2006
TLS 1.2
2008
TLS 1.3
dra

7. PUBLIC/PRIVATE KEY
ENCRYPTION

9. Math time!
p = 11, q = 17 // two prime numbers
modulus = 187 // p * q
e = 3 // random number between 1 and modulus
// find d, so that (d * e) - 1 % (p - 1) * (q - 1) is zero
320 % 160 = 0
(321 - 1) % (10 * 16) = 0
(107 * 3) = 321 → d = 107
Note that d varies with e:
e = 7
// find d, so that (d * e) - 1 % (p - 1) * (q - 1) is zero
1280 % 160 = 0
(1281 - 1) % (10 * 16) = 0
(183 * 7) = 1281 → d = 183

10. Now, what if and are unknown?p q
p = 13 // prime number
q = 23 // prime number
modulus = 299 // p * q
e = 5 // random number between 1 and modulus
// find d, so that (d * e) - 1 % (p - 1) * (q - 1) is zero
1584 % 264 == 0
(1585 - 1) % (12 * 22) = 0
(317 * 5) = 1585 → d = 317
Turns out this is pretty hard!

11. For big enough and , finding those factors will cost an
eternity!
p q
So we can distribute ( p * q ) and even e!

12. d = 107
LET'S ENCRYPT THE LETTER 'G'
G → 7
7e → 73 → 343
343 % 187 → 156
LET'S DECRYPT THE MESSAGE '156'
156107 → 4.6 * 10234
156107 % 187 → 7
7 → G

14. Negotiating a secure
connection
Client Server
1 ClientHello →
2 ← ServerHello
3 ← Certificate
4 ← ServerKeyExchange
5 ← ServerHelloDone
6 ClientKeyExchange →
7 ChangeCipherSpec →
8 Finished →
9 ← ChangeCipherSpec
10 ← Finished

15. DEMO TIME!
No-one is eavesdropping!

16. SIGNED CERTIFICATES

17. Certificate contents
Serial Number
Subject
Validity
Usage
Public Key
Fingerprint
Algorithm
Fingerprint

18. But wait... anyone could create a certificate!
So we also need
Signature
Algorithm
Signature
Issuer
... and a way to sign stuff

20. A is a mathematical relationship between a
message , a private key and a public key .
signature
x sk pk
It consists of two functions:
1. signing function
2. verifying function
t = f (sk, x)
[accept, reject] = g(pk, t, x)
So, given x and t and knowing pk,
we can tell if x is indeed signed by sk.

21. CERTIFICATE
AUTHORITIES

22. An entity that issues digital certificates, certifying the
ownership of a public key by the subject of the certificate.

23. "I can trust you, because I trust John, and John trusts Alice,
and Alice trusts you"
I
John
?
Alice
Who knows who "John" is?
Many "John"'s in todays browsers and operating systems!

24. Top-notch security procedures, including "key ceremonies"
And yet...

25. FAIRYTALE TIME!
Once upon a time, a Dutch certificate
authority named DigiNotar was living
happily and carefree in the town of
Beverwijk.
But on a bad day, evil hurt it...
Real hard.

26. An attacker compromised a webserver of
DigiNotar due to a vulnerability that is
present within the DotNetNuke so ware.
DotNetNuke version 4.8.2.0 is installed on
host winsrv119. This version is affected by a
file upload vulnerability.

27. Due to the weak security of Windows
passwords it must be assumed that the
attacker was able to compromise the
passwords [...] of the accounts found on the
system. On the system, [...] the domain
administrator account [...] is present.

28. The attacker was able to traverse the
infrastructure and obtain access to at least
two CA's that were used to generate
certificates.

29. <!-- intentionally le blank -->

30. Google blacklists 247 certificates in Chromium
Microso removes the DigiNotar root certificate from all
supported Windows-releases *
Mozilla revokes trust in the DigiNotar root certificate in all
supported versions
Apple issued Security Update 2011-005
Update Certificate Revocation Lists (except these are
self-signed)

31. DEMO TIME!
Trust (for what it's worth)

32. TOOLS
curl -v -k <address>
openssl s_client -showcerts -servername
<address> -connect <address>:443

33. Denotes where a can be found: a file that contains
.
is the password to that file.
JVM SETTINGS (1)
-Djavax.net.ssl.trustStore=<file>
truststore
trusted certs
-Djavax.net.ssl.trustStorePassword=...

34. Denotes where a can be found: a file that contains
.
is the password to that file.
JVM SETTINGS (2)
-Djavax.net.ssl.keyStore=<file>
keystore
private keys
-Djavax.net.ssl.keyStorePassword=...

35. Include debug logging for TLS handshake and connections.
JVM SETTINGS (3)
-Djavax.net.debug=all

36. Portecle

37. SO LONG
AND THANKS FOR ALL THE FISH
IMAGE ATTRIBUTIONS
Beverwijk by @ .Gerard Hogervorst Wikimedia Commons