Novel Instruction Set Architecture Based Side Channels in popular SSL/TLS Implementations

NOVEL SIDE CHANNELS IN POPULAR SSL/TLS IMPLEMENTATIONS BASED ON INSTRUCTION SET ARCHITECTURE

By : Vaishali Garg

1

BACKGROUND 2

PADDING ORACLE ATTACK

¢ Against CBC-mode encryption with PKCS#5 padding

¢ Oracle exists which on receipt of ciphertext, decrypts it & replies whether the padding is correct or not

¢ Using this oracle, data can be decrypted without knowing the key 3

Vaudenay’s Attack

May 2002

PADDING ORACLE ATTACK REVIVED

4

Aug 2012

Dec 2014

Jan 2010

Oct 2014

ATTACKS BASED ON PACKET COMPRESSION SIZE

5

Sep 2012

July 2013 (Revival of CRIME)

SIDE CHANNEL ATTACKS

¢  Information gained from physical implementation of a cryptosystem

�  Through some observable attributes of an online communication

¢  Example : �  Packet Arrival & Departure time or an error message �  Packet Size �  Power Usage

6

RESEARCH DIRECTION

¢ Side-channel attacks keep on reviving

¢ Such multiple side channels may exist

¢ To determine novel side channels in various open source SSL libraries such as OpenSSL and wolfSSL

7

PADDING ORACLE ATTACK 8


9

http://www.bank.com/login.php?message= b2a72189df804632a55a15d599a1693e6e62a997052847fd

b2a72189df804632

IV

a55a15d599a1693e

Block 1

6e62a997052847fd

Block 2

https://www.bank.com/login.php?message=transfer10x06x06x06x06x06x06

3-DES, AES, RSA etc.


10

6e 62 a9 97 05 28 47 fd

Decrypt

??

?? ?? ?? ?? ?? ?? ?? 01

Intermediate block

Previous block

Plaintext block

IV

?? ?? ?? ?? ?? ?? ?? ??

00 00 00 00 00 00 00

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ??

?? 00 00 00 00 00 00 00

??

Decrypt

Block 1 Block 2

Valid padding check


11

Incorrect padding Correct padding

Response time - more Response time - less

Further decryption takes place

No Further decryption

6e 62 a9 97 05 28 47 fd

Decrypt

??

?? ?? ?? ?? ?? ?? ?? 01

Intermediate block

Previous block

Plaintext block

IV

?? ?? ?? ?? ?? ?? ?? ??

00 00 00 00 00 00 00

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ??

?? 00 00 00 00 00 00 00

??

Decrypt

means, A XOR B = 0x01

?? XOR ?? = 01


12

Block 1 Block 2 Brute force

¢  Brute Force the Last Byte – from 0x00-0xff

13

The Oracle

00 00 00 00 00 00 00

6e 62 a9 97 05 28 47 fd

00 C1

C2

64 32 1b b8 0a aa 08 39

P2

Incorrect padding, immediate server response

Error 404 : Server not found :(

The Oracle

00 00 00 00 00 00 00

6e 62 a9 97 05 28 47 fd

39 C1

C2

64 32 1b b8 0a aa 08 01

P2

Correct padding, server response takes some time

Error 404 : Server not found :(

01

39


14

Server Response

Server Response Time

(same in all cases)

(different for valid padding case)

PADDING ORACLE ATTACK So, C2’ xor C1 = 0x01

C2’ xor 0x39 = 0x01 implies, C2’ = (0x39) xor (0x01)

C2’ = 0x38 (intermediate byte of C2) ---- (1)

6e 62 a9 97 05 28 47 fd

Decrypt

?? ?? ?? ?? ?? ?? ?? 01

IV

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

39

00 00 00 00 00 00 00

00 00 00 00 00 00 00 39

Decrypt

means, C2’ XOR C1 = 0x01

?? XOR 39 = 01

C1 = a55a15d599a1673e ---(2) C2 = 6e62a997052847fd

15

From CBC Decryption P2 = (Intermediate byte of C2) xor (C1) P2 = (0x38) xor (0x3e) P2 = 0x06

Hence, Plaintext is successfully obtained

C1 C2

Big Question

16

Are these the only side channels? Or Can there be other instruction set architecture based side channels?

17

EXAMPLES ¢  Some instructions are executed more often for valid

padding

¢  Example : �  CPU cycles �  Memory Accesses

18

CONTRIBUTION

¢ Explored Novel Side Channels on OpenSSL & wolfSSL �  Based on Instruction Set Architecture �  Examples : CPU cycles, Memory Accesses etc.

¢ Successful decryption of cipher text using aforementioned side channels �  Change in the value of the attributes �  Clearly Observable for correct plaintext value �  Decipher all bytes

19

OPENSSL 20

OPENSSL �  Full featured open source toolkit �  Implements SSL(v2/v3) & TLS protocols(v1) �  Support for various cryptographic functions �  Used id Open Source Projects like TOR, IPSEC Tools, APT package

manager

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Source : http://arstechnica.com/security/2014/04/critical-crypto-bug-in-openssl-opens-two-thirds-of-the-web-to-eavesdropping/

RESEARCH APPROACH 22

Research Approach

255 ciphertext variants

Attributes Data

128-bit AES encryption

Ciphertext

GEM5 simulator

AES decryption static binary

Statistical Analysis

User

Actual System 23

GEM5 SIMULATOR ¢  Computer system simulation platform ¢  Supports various ISAs : Alpha, ARM, MIPS, Power, SPARC,

and x86 ¢  Two modes :

�  System Emulation : ¢  Used for running individual applications or set of applications ¢  Used if you want do research on a particular application

�  Full System Emulation : ¢  Used For booting OS ¢  Used if you want to do research on how does the OS effects our

application or devices ¢  Stats for Instruction Set Architecture related attributes

such as : �  Instructions committed �  Integer register reads & writes �  ALU accesses �  Arithmetic operations completed & many more… 24

IMPLEMENTATION AND EVALUATION

25

OPENSSL

OpenSSL

Desktop Mobile Stock

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PERL (CPAN)

00000000000000000000000000000000 dc95342e176fe8f26e62a997052847fd

00000000000000000000000000000001 dc95342e176fe8f26e62a997052847fd

00000000000000000000000000000002 dc95342e176fe8f26e62a997052847fd

000000000000000000000000000000ff dc95342e176fe8f26e62a997052847fd

Attack Approach – On AES-128 bit

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Plaintext : zmx4wker02g6HELLOHOWSUqA (24 bytes) zmx4wker02g6HELLOHOWSUqAx08x08x08x08x08x08x08x08x08(32 bytes)

Ciphertext : 52cb50912065ac52a55a15d599a16930dc95342e176fe8f26e62a997052847fd (32 bytes)

GEM5 simulator

128-bit AES decryption static

binary

OPENSSL RESULTS 28

OPENSSL RESULTS ¢ For Last Byte

29

205471

205472

205473

205474

205475

205476

205477

00.lo

g 06

.log

0c.lo

g 12

.log

18.lo

g 1e

.log

24.lo

g 2a

.log

30.lo

g 36

.log

3c.lo

g 42

.log

48.lo

g 4e

.log

54.lo

g 5a

.log

60.lo

g 66

.log

6c.lo

g 72

.log

78.lo

g 7e

.log

84.lo

g 8a

.log

90.lo

g 96

.log

9c.lo

g a2

.log

a8.lo

g ae

.log

b4.lo

g ba

.log

c0.lo

g c6

.log

cc.lo

g d2

.log

d8.lo

g de

.log

e4.lo

g ea

.log

f0.lo

g f6

.log

fc.lo

g

No.

of

Inte

ger

Mul

tipl

icat

ions

Last Byte

Integer Multiplications At last byte = 0x39

OPENSSL RESULTS

¢ For Second Last Byte

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98594000 98595000 98596000 98597000 98598000 98599000 98600000 98601000 98602000

00.lo

g 06

.log

0c.lo

g 12

.log

18.lo

g 1e

.log

24.lo

g 2a

.log

30.lo

g 36

.log

3c.lo

g 42

.log

48.lo

g 4e

.log

54.lo

g 5a

.log

60.lo

g 66

.log

6c.lo

g 72

.log

78.lo

g 7e

.log

84.lo

g 8a

.log

90.lo

g 96

.log

9c.lo

g a2

.log

a8.lo

g ae

.log

b4.lo

g ba

.log

c0.lo

g c6

.log

cc.lo

g d2

.log

d8.lo

g de

.log

e4.lo

g ea

.log

f0.lo

g f6

.log

fc.lo

g

No.

of

Inte

ger

Reg

iste

r R

eads

Second Last Byte

Integer Register Reads At second last byte = 0x63

REASON FOR VARIATION

31

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16

WOLFSSL 32

WOLFSSL

�  Lightweight embedded SSL library (20 times smaller than OpenSSL)

�  Small footprint size(30-100kB) & low runtime memory usage(3-36kB)

�  Targeted for embedded devices, RTOS & environments facing constraints in computational resources

�  Major uses in MySQL, wireless sensors used in power grids etc.

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Various Projects using wolfSSL Products

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00000000000000000000000000000000 5145ea93c3b647860c13228d8dc1e90c

Attack Approach – On AES–128 bit

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Plaintext : POST/gp/redirect/indi.htmlCookie:token=wdH (42 bytes) POST/gp/redirect/indi.htmlCookie:token=wdHx06x06x06x06x06x06(48 bytes)

Ciphertext : c5421b878c2d36a052f45796ad1bdea11d501312a305f586369cd8e19136db095145ea93c3b647860c13228d8dc1e90c (48 bytes)

GEM5 simulator

128-bit AES decryption static

binary

00000000000000000000000000000001 5145ea93c3b647860c13228d8dc1e90c

00000000000000000000000000000002 5145ea93c3b647860c13228d8dc1e90c

000000000000000000000000000000ff 5145ea93c3b647860c13228d8dc1e90c

WOLFSSL RESULTS ¢ For Last Byte

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448100000

448120000

448140000

448160000

448180000

448200000

00.lo

g 07

.log

0e.lo

g 15

.log

1c.lo

g 23

.log

2a.lo

g 31

.log

38.lo

g 3f

.log

46.lo

g 4d

.log

54.lo

g 5b

.log

62.lo

g 69

.log

70.lo

g 77

.log

7e.lo

g 85

.log

8c.lo

g 93

.log

9a.lo

g a1

.log

a8.lo

g af

.log

b6.lo

g bd

.log

c4.lo

g cb

.log

d2.lo

g d9

.log

e0.lo

g e7

.log

ee.lo

g f5

.log

fc.lo

g

No.

of

Inte

ger

Reg

iste

r R

ead

s

Last Byte

Integer Register Reads At a value where plaintext

byte becomes 0x00

POODLE ATTACK

37

POODLE ATTACK

¢ Attacker’s interest is in secret token or cookie

CSRF Attack 38

POODLE ATTACK ¢ An encrypted post request looks as follows : ¢ An attacker can control both the request path & the request

body ¢ Hence, he can generate requests such that following two

conditions hold : a)  The padding fills an entire block (encrypted into Cn). b)  The cookies’ first as of yet unknown byte appears as the final byte

in an earlier block (encrypted into Ci).

POST /path Cookie: name=value...\r\n\r\nbody || 20byte MAC || padding

39

POODLE ATTACK ¢ Example original plaintext :

POST/gp/redirect/indi.htmlCookie:token=wdHZJaxBe……….

Attacker can modify this plaintext size as multiple of block size (say 8) & hence the padding will fill one complete last block which encrypts into Cn

48 Bytes

First Condition fulfilled

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POODLE ATTACK ¢  To fulfill the second condition the plaintext is changed in this

manner :

Encrypts into Ci-1 Encrypts into Ci

Iteration 1

Iteration 2

Iteration 3

Iteration 4

41

Unknown byte appears as Final byte of a 8 byte block

POODLE ATTACK ¢  Cipher text corresponding to First Iteration :

¢  Replace Cn with Ci

Ciphertext : 5f06fc6cc5ff7b230fdcf40b1d0603ca0067df2ec6a8f3be0067df2ec6a8f3be5c48fe596cca889fb4e07a3571aac7ad26b8d80ac480904bb075cbf233b4d6298bf5816a3d3dca5fa7d5261e44b0ce4a545f137188deb3a49446a30343a09e38a73b3e45bd96efbb

Cn Ci

Ciphertext : 5f06fc6cc5ff7b230fdcf40b1d0603ca0067df2ec6a8f3be0067df2ec6a8f3be5c48fe596cca889fb4e07a3571aac7ad26b8d80ac480904bb075cbf233b4d6298bf5816a3d3dca5fa7d5261e44b0ce4a545f137188deb3a49446a30343a09e385c48fe596cca889f

Cn / Ci

Ci-1

Ci-1 42

POODLE ATTACK

43

0000000000000000 5c48fe596cca889f GEM5 simulator

3-DES decryption static binary

0000000000000001 5c48fe596cca889f

0000000000000002 5c48fe596cca889f

00000000000000ff 5c48fe596cca889f

WOLFSSL RESULTS 44

WOLFSSL RESULTS ¢ For Last Byte

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122525000

122530000

122535000

122540000

122545000

122550000

122555000

00.lo

g 07

.log

0e.lo

g 15

.log

1c.lo

g 23

.log

2a.lo

g 31

.log

38.lo

g 3f

.log

46.lo

g 4d

.log

54.lo

g 5b

.log

62.lo

g 69

.log

70.lo

g 77

.log

7e.lo

g 85

.log

8c.lo

g 93

.log

9a.lo

g a1

.log

a8.lo

g af

.log

b6.lo

g bd

.log

c4.lo

g cb

.log

d2.lo

g d9

.log

e0.lo

g e7

.log

ee.lo

g f5

.log

fc.lo

g No

. o

f M

emo

ry

Ref

eren

ces

Last Byte

Memory References Maximum value at byte = 0xc9

POODLE ATTACK

So, Cn’ xor Cn-1 = 0x00 Cn’ xor 0xc9 = 0x00

implies, Cn’ = (0xc9) xor (0x00) Cn’ = 0xc9 (intermediate byte of Cn/Ci)

5c 48 fe 59 6c ca 88 9f

Decrypt

?? ?? ?? ?? ?? ?? ?? 00

IV

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

?? ?? ?? ?? ?? ?? ?? ??

39

00 00 00 00 00 00 00

00 00 00 00 00 00 00 39

Decrypt

means, Cn’ XOR Cn-1 = 0x01

?? XOR 39 = 00

Ci-1 = 0067df2ec6a8f3be Ci/Cn = 5c48fe596cca889f

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From CBC Decryption Pi = (Intermediate byte of Ci) xor (Ci-1) Pi = (0xc9) xor (0xbe) Pi = 0x77 [Hex value for ‘w’]

Hence, cookie’s first unknown byte is revealed

Cn-1 Cn / Ci

WOLFSSL RESULTS

¢ For Second Last Byte

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246070000

246080000

246090000

246100000

246110000

246120000

246130000

246140000

00.lo

g 07

.log

0e.lo

g 15

.log

1c.lo

g 23

.log

2a.lo

g 31

.log

38.lo

g 3f

.log

46.lo

g 4d

.log

54.lo

g 5b

.log

62.lo

g 69

.log

70.lo

g 77

.log

7e.lo

g 85

.log

8c.lo

g 93

.log

9a.lo

g a1

.log

a8.lo

g af

.log

b6.lo

g bd

.log

c4.lo

g cb

.log

d2.lo

g d9

.log

e0.lo

g e7

.log

ee.lo

g f5

.log

fc.lo

g

No.

of

com

mit

ted

in

stru

ctio

ns

Second Last Byte

Committed CPU Instructions Maximum value at byte = 0xf1

REASON FOR VARIATION

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

TAKEAWAYS

¢ Many Side-channels have effected cryptographic libraries

�  These side channels have revived very often

�  Instruction based side channels haven’t been explored

¢ OpenSSL and wolfSSL previously patched against padding oracle and POODLE attack

¢ We explored novel side-channels on popular SSL/TLS Implementations – eg. Memory accesses, CPU instructions etc.

¢ Successfully decipher all plaintext bytes 49

FUTURE WORK ¢  We performed it in simulation environment which has

its own bottleneck. Other tool which can give faster results can be used.

¢  We have used one API for OpenSSL & wolfSSL. Other APIs can be explored.

¢  Other cryptographic Libraries can be explored.

¢  Real Life Applications can be studied

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REFERENCES �  Ivanov, A. (2005). Side-Channel Attacks. �  Skorobogatov, Sergei. "Side-channel attacks." �  Lomne, Victor, et al. "Side Channel Attacks." Security Trends for FPGAS.

Springer Netherlands, 2011. 47-72. �  Peeters, Eric, et al. "Improved higher-order side-channel attacks with

FPGA experiments." Cryptographic Hardware and Embedded Systems–CHES 2005. Springer Berlin Heidelberg, 2005. 309-323.

�  Black, John, and Hector Urtubia. "Side-Channel Attacks on Symmetric Encryption Schemes: The Case for Authenticated Encryption." USENIX Security Symposium. 2002.

�  Vaudenay, Serge. "Security Flaws Induced by CBC Padding—Applications to SSL, IPSEC, WTLS..." Advances in Cryptology—EUROCRYPT 2002. Springer Berlin Heidelberg, 2002.

�  Paterson, Kenneth G., and Arnold Yau. "Padding oracle attacks on the ISO CBC mode encryption standard." Topics in Cryptology–CT-RSA 2004. Springer Berlin Heidelberg, 2004. 305-323.

�  Yau, Arnold KL, Kenneth G. Paterson, and Chris J. Mitchell. "Padding oracle attacks on CBC-mode encryption with secret and random IVs." Fast Software Encryption. Springer Berlin Heidelberg, 2005.

�  Rizzo, Juliano, and Thai Duong. "Practical Padding Oracle Attacks." WOOT. 2010.

�  Duong, Thai, and Juliano Rizzo. "Padding oracles everywhere." (2010). 51

REFERENCES �  Kaliski, Burt. "PKCS# 7: Cryptographic Message Syntax Version 1.5." (1998). �  Möller, Bodo, Thai Duong, and Krzysztof Kotowicz. "This POODLE Bites:

Exploiting The SSL 3.0 Fallback." (2014). �  Binkert, Nathan, et al. "The gem5 simulator." ACM SIGARCH Computer

Architecture News 39.2 (2011): 1-7. �  Gluck, Yoel, Neal Harris, and Angelo Prado. "BREACH: reviving the CRIME

attack." �  Irazoqui, Gorka, et al. "Lucky 13 Strikes Back." Proceedings of the 10th

ACM Symposium on Information, Computer and Communications Security. ACM, 2015.

�  Blatz, Jeremiah. "CSRF: Attack and Defense." McAfee® Foundstone® Professional Services, White Paper (2007).

�  Johny, Alphonsa. "Secure Socket Layer Implementations-A." �  Kumar, Uday, Tuhin Borgohain, and Sugata Sanyal. "Comparative Analysis of

Cryptography Library in IoT." arXiv preprint arXiv:1504.04306 (2015). �  Krawczyk. " The Order of Encryption and Authentication for Protecting

Communications." CRYPTO 2001 �  Juliano Rizzo, Thai Duong."Here Come The Ninjas."Ekoparty 2011 �  Juliano Rizzo, Thai Duong."The CRIME Attack."Ekoparty 2012

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THANK YOU

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Novel Instruction Set Architecture Based Side Channels in popular SSL/TLS Implementations

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Transcript of Novel Instruction Set Architecture Based Side Channels in popular SSL/TLS Implementations