TLSeminar: Introduction

cs6501: Understanding and Securing TLS
University of Virginia, Spring 2017
https://tlseminar.github.io/

Transcript

1. TLSeminar: Introduction David  Evans University  of  Virginia tlseminar.github.io 20  January  2017
2. Why  a  whole  seminar  on  TLS? 1
6. Secure  Web  Connections 5 Client (Browser) MightBeEvil.org Server
7. Secure  Web  Connections 6 Client (Browser) MightBeEvil.org Server Image:  https://unsplash.com/@brenomachado
8. Secure  Web  Connections 7 Client (Browser) MightBeEvil.org Server Image:  https://unsplash.com/@brenomachado How  can  we  know: (1)We  are  talking  to  the  intended  server (2)No  one  in  the  middle  can  observe  or  alter  the  content
9. Encryption 8 Encrypt Decrypt Plaintext Ciphertext Plaintext Insecure  Channel Key Key Symmetric  Crypto: channel  encrypted  with  shared  secret  key. Bob MightBeEvil.org Alice Client (Browser) Server
10. Symmetric  Encryption   9 Jefferson’s  Cipher  Wheel (1802) “on  the  periphery  of   each,  and  between   the  black  lines,  put  all   the  letters  of  the   alphabet,  not  in  their   established  order,  but   jumbled,  &  without   order,  so  that  no  two   shall  be  alike.”  
11. Modern  Symmetric  Encryption 10 AES  Round 128  or  more  key  bits ~1017 J needed  for  most  efficient   possible  brute  force  attack Very  inexpensive:  instructions   built  in  to  most  processors
12. Modern  Symmetric  Encryption 11 AES  Round 128  or  more  key  bits ~1017 J needed  for  most  efficient   possible  brute  force  attack Very  inexpensive:  instructions   built  in  to  most  processors
13. Secure  Web  Connections 12 Client (Browser) MightBeEvil.org Server Image:  https://unsplash.com/@brenomachado How  can  we  know: (1)We  are  talking  to  the  intended  server ü No  one  in  the  middle  can  observe  or  alter  the  content
14. Asymmetric  (Public  Key)  Encryption:   Confidentiality 13 Encrypt Decrypt Plaintext Ciphertext Plaintext Bob’s  Public  Key Bob’s  Private  Key Alice Bob Insecure  Channel Asymmetric  Crypto: Alice  obtains  Bob’s  Public  Key,  and  can  send   private  messages  to  Bob.
15. 14 Client Server Hello I’m  “mightbeevil.org”  and   my  public  key  is   Generate   random   () Decrypt  using   Secure  channel  using   Super-­‐Simplified  TLS  Protocol Generates  key  pair: ,  
16. 15 Encrypt Decrypt Plaintext Ciphertext Plaintext Bob’s  Public  Key Bob’s  Private  Key Alice Bob Insecure  Channel Signatures: Bob’s  signs  a  message  with  his  Private  Key;   Alice  verifies  signature  with  Bob’s  Public  Key. Asymmetric  (Public  Key)  Encryption:   Confidentiality Signatures
17. 16 Client Server Hello Sign (“mightbeevil.org”   has  public  key   ) Generate   random   () Decrypt  using   Secure  channel  using   Super-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using  
18. goto fail; 17
19. 18 static  OSStatus SSLVerifySignedServerKeyExchange(SSLContext *ctx,  bool isRsa,  SSLBuffer signedParams, uint8_t  *signature,  UInt16  signatureLen)  { … if  ((err  =  SSLHashSHA1.update(&hashCtx,  &clientRandom))  !=  0) goto fail; if  ((err  =  SSLHashSHA1.update(&hashCtx,  &serverRandom))  !=  0) goto fail; if  ((err  =  SSLHashSHA1.update(&hashCtx,  &signedParams))  !=  0) goto fail; goto fail; if  ((err  =  SSLHashSHA1.final(&hashCtx,  &hashOut))  !=  0) goto fail; err  =  sslRawVerify(ctx,  ctx-­‐>peerPubKey,  dataToSign,  dataToSignLen,  signature,  signatureLen); if(err)  { sslErrorLog("SSLDecodeSignedServerKeyExchange:  sslRawVerify returned  %d\n",  (int)err); goto fail; } fail: SSLFreeBuffer(&signedHashes); SSLFreeBuffer(&hashCtx); return  err; } Apple’s  Implementation (cleaned  up  and  excerpted)
20. 19 Client Server Hello Sign (“mightbeevil.org”   has  public  key   ) Generate   random   () Decrypt  using   Secure  channel  using   Super-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using   How  does  the  server  get  its  certificate?
21. Certificates 20 VarySign.com virginia.edu virginia.edu,   Generates  key  pair: ,   Sign (“virginia.edu”  has  public  key   ) $$$
27. 26 Client Server Hello Sign (“mightbeevil.org”has public  key  is   ) Generate   random   () Decrypt  using   Secure  channel  using   Super-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using   How  does  the  client  (browser)  get   ?
29. 28 Client Server Hello Sign (“mightbeevil.org”has public  key  is   ) Generate   random   () Decrypt  using   Secure  channel  using   Super-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using  
30. 29 Client Server Hello,  Ciphers:  [...,  RSA-­‐1024,  DHE,  …] Sign (“mightbeevil.org”has public  key  is   ), Cipher:  RSA-­‐1024 Generate   random   () Decrypt  using   Secure  channel  using   Slightly  Less-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using   Picks  ciphers  to  use
31. 30 Client Server Hello,  Ciphers:  [...,  RSA-­‐1024,  …] Sign (“mightbeevil.org”has public  key  is   ), Cipher:  DH-­‐E Generate   random   () Decrypt  using   Secure  channel  using   Slightly  Less-­‐Simplified  TLS  Protocol Generates  key  pair: ,   Verify   Certificate   using   Picks  ciphers  to  use
32. Why  Weak  Ciphers  are  Supported? 31 Client Hello,  Ciphers:  [...,  RSA-­‐1024,  …] Sign (“mightbeevil.org”has public  key  is   ), Cipher:  DHE-­‐E Hello,  Ciphers:  [DHE-­‐E,  …]
35. 34 Padding  Oracle  Attacks  (Week  2) Breaking  weak  RSA,  DROWN  attack  (Week  3)  
36. Rest  of  Today 35 1. Organize  Teams 2. Bid  for  Roles (today’s  Blog  team: updated  version  of   first  few  milliseconds) 3.  Talk  about  project 4.  Start  exploring  TLS  connections
37. Seminar  Plan 36
39. Class  Lead  Team • Two  weeks  before:  idea  for  class • One  week  before:  full  plan  for  class,  selected   preparation  materials – Post  for  class  in  Slack • Class:  lead  an  interesting,  engaging,  worthwhile  class – Not  just  presenting  papers  (although  that  should  usually   be  part  of  it) – We  have  2.5  hours  – need  to  plan  accordingly!   • Post-­‐class:  help  blogging  team 38
40. Class  Blogging  Team • Write  a  blog  post  about  class  topic – Incorporate  materials  provided  by  Lead  team – Organize  into  useful  and  effective  web   presentation • Draft  due  by  following  Tuesday • Final  version  ready  by  next  Friday 39
41. Food Team 40
42. Now:  Organize  your  Teams • Management  Structure – Need  to  have  people  willing  to  lead  and  delegate – Can  rotate  throughout  semester – Roles  for  each  week • Create  (public)  Slack  channel – If  you  want  a  team-­‐private  channel  can  do  that  also • Bid  for  T (lead  Class  2:  oracle  padding  attacks) L (blog  Class  1/lead  3:  Drown) S (lead  Class  4:  certificates) 41
44. Project • Teams  of  1-­‐24  people • Do  something  that: – Contributes  useful  to  TLS  ecosystem – Possibilities:  research  project,  contributing  to   open  source  software,  deployment  studies,   alternatives  to  TLS,  measurement  study,  etc. 43
45. Rest  of  Today 44 1. Organize  Teams 2. Bid  for  Roles (today’s  Blog  team: updated  version  of   first  few  milliseconds) 3.  Talk  about  project 4.  Start  exploring  TLS  connections