Soviet Russia Smartcard Hacks You
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The document presents an overview of smartcard vulnerabilities, highlighting the role of smartcards in authentication systems and their inherent risks. Eric Sesterhenn discusses various protocols, fuzzing techniques, and the importance of understanding trust models in security measures. The presentation encourages proactive engagement with open-source projects to enhance security and advocacy for comprehensive testing methods.
![Apple Smartcardservices
do {
cacreturn = cacToken.exchangeAPDU(command, sizeof(command), result,
resultLength);,!
if ((cacreturn & 0xFF00) != 0x6300)
CACError::check(cacreturn);
...
memcpy(certificate + certificateLength, result, resultLength - 2);
certificateLength += resultLength - 2;
// Number of bytes to fetch next time around is in the last byte
// returned.
command[4] = cacreturn & 0xFF;
} while ((cacreturn & 0xFF00) == 0x6300);
DEF CON 2018 15 / 30](https://image.slidesharecdn.com/defcon-26-eric-sesterhenn-soviet-russia-smartcard-hacks-you-180925051850/85/Soviet-Russia-Smartcard-Hacks-You-15-320.jpg)
![OpenSC - CryptoFlex
u8 buf[2048], *p = buf;
size_t bufsize, keysize;
sc_format_path("I1012", &path);
r = sc_select_file(card, &path, &file);
if (r)
return 2;
bufsize = file->size;
sc_file_free(file);
r = sc_read_binary(card, 0, buf, bufsize, 0);
DEF CON 2018 16 / 30](https://image.slidesharecdn.com/defcon-26-eric-sesterhenn-soviet-russia-smartcard-hacks-you-180925051850/85/Soviet-Russia-Smartcard-Hacks-You-16-320.jpg)
Soviet Russia Smartcard Hacks You
- 1. Eric Sesterhenn <[email protected]> 2018 X41 D-SEC GmbH https://www.x41-dsec.de/ 1 / 30
- 2. whoami • Eric Sesterhenn • Principal Security Consultant • Pentesting/Code Auditing at X41 https://www.x41-dsec.de/ 2 / 30
- 3. Disclaimer • The issues presented here have been reported and fixed! • These are open source projects - help them! • I am not interested in testing / debugging proprietary stuff in my spare time. DEF CON 2018 3 / 30
- 4. Targets LINUX LOGIN DEF CON 2018 4 / 30
- 5. Why? • Smartcards control authentication! • Authentication runs as root! • Users and programmers subconsciously trust the smartcard! DEF CON 2018 5 / 30
- 6. Smartcards User Smartcard Reader Reader Driver (PC/SC) Login (pam) Smartcard Driver (OpenSC) DEF CON 2018 6 / 30
- 7. What is a Smartcard? • Physical, tamper-proof device • Designed to keep information secret • Contains memory and a processor https://en.wikipedia.org/wiki/Smart_card#/media/File:SmartCardPinout.svg DEF CON 2018 7 / 30
- 8. Application Protocol Data Unit • APDUs form the protocol to talk to smartcards • ISO/IEC 7816-4 Identification cards - Integrated circuit cards • T=0 is character oriented / T=1 is block-oriented • Verify: 00 20 00 01 04 31323334 CLA INS P1 P2 LC Data 1 1 1 1 0-3 NC DEF CON 2018 8 / 30
- 9. PC/SC API • PC/SC API can be used on win and *nix • Other libraries have a similar interface LONG WINAPI SCardTransmit( SCARDHANDLE hCard, LPCSCARD_IO_REQUEST pioSendPci, LPCBYTE pbSendBuffer, DWORD cbSendLength, PSCARD_IO_REQUEST pioRecvPci, LPBYTE pbRecvBuffer, LPDWORD pcbRecvLength ); DEF CON 2018 9 / 30
- 10. PKCS11 • PKCS11 is a platform independent API for cryptographic token • Supported by OpenSSL, browsers,... (eg. via libp11) • Windows uses smartcard Minidriver now • Driver for each card, uses ATR to match CK_RV C_FindObjectsInit( CK_SESSION_HANDLE hSession, CK_ATTRIBUTE_PTR pTemplate, CK_ULONG ulCount ); DEF CON 2018 10 / 30
- 11. Smartcard Stack Summary Application (pam) PKCS11 PC/SC APDU Physical Card DEF CON 2018 11 / 30
- 12. Smartcard for Sign-On PAM Smartcard CRLServer GetCerti cates Certi cate Validate Certi cate and User RevocationCheck CRL GenerateNonce SignRequestforNonce Signature CheckSignatureAgainstCerti cate DEF CON 2018 12 / 30
- 13. Trust the Smartcard • Driver developers trust the smartcard! • Let’s abuse that • Mess with the card responses DEF CON 2018 13 / 30
- 14. # Bugs Project # Bugs libykneomgr 1 OpenSC Over 9000 ;-) pam_pkcs11 1 smartcardservices 2 Yubico-Piv 2 No, I did not fuzz the &$#?@! out of it... but guess which one I fuzzed the most ;-) Thanks to Frank Morgner for fixing! DEF CON 2018 14 / 30
- 15. Apple Smartcardservices do { cacreturn = cacToken.exchangeAPDU(command, sizeof(command), result, resultLength);,! if ((cacreturn & 0xFF00) != 0x6300) CACError::check(cacreturn); ... memcpy(certificate + certificateLength, result, resultLength - 2); certificateLength += resultLength - 2; // Number of bytes to fetch next time around is in the last byte // returned. command[4] = cacreturn & 0xFF; } while ((cacreturn & 0xFF00) == 0x6300); DEF CON 2018 15 / 30
- 16. OpenSC - CryptoFlex u8 buf[2048], *p = buf; size_t bufsize, keysize; sc_format_path("I1012", &path); r = sc_select_file(card, &path, &file); if (r) return 2; bufsize = file->size; sc_file_free(file); r = sc_read_binary(card, 0, buf, bufsize, 0); DEF CON 2018 16 / 30
- 17. Popping calcs... DEF CON 2018 17 / 30
- 18. Basic Smartcard Exploitation in 2018 • Basiccard gives you nice control,... yes BASIC! • Example exploit (Kevin) will be released to the public at beVX • Other methods would be SIMtrace or certain Javacards DEF CON 2018 18 / 30
- 19. YUBICO PIV if(*out_len + recv_len - 2 > max_out) { fprintf(stderr, "Output buffer to small, wanted to write %lu, max was %lu.", *out_len + recv_len - 2, max_out); ,! ,! } if(out_data) { memcpy(out_data, data, recv_len - 2); out_data += recv_len - 2; *out_len += recv_len - 2; } DEF CON 2018 19 / 30
- 20. Logging in... DEF CON 2018 20 / 30
- 21. Challenges in fuzzing a protocol • Most modern fuzzers are file-oriented • Radamsa: Generates a corpus of files • Hongfuzz: passes a file (filename different each run) • libfuzzer: passes a buffer and length • AFL: passes a file DEF CON 2018 21 / 30
- 22. Challenges in fuzzing a protocol • SCardTransmit() tells us how much data it expects • Read this from a file on each call and error out if EOF • No complicated poll handling like for network sockets required DEF CON 2018 22 / 30
- 23. How to fuzz - OpenSC • reader-fuzzy.c • Implements a (virtual) smartcard reader interface • Responds with malicious data read from file (OPENSC_FUZZ_FILE) • Have fun with AFL American Fuzz Lop pkcs11-tool -t libopensc card-cac.c reader-fuzzy.c Fuzzing File Input DEF CON 2018 23 / 30
- 24. How to fuzz - Winscard and PC/SC • Winscard(.dll) on Linux and Unix • For proprietary code • Preload the library • Have fun with non-feedback fuzzers (e.g. radamsa) or AFL in qemu mode DEF CON 2018 24 / 30
- 25. How to fuzz - Winscard 2 • Tavis loadlibrary • Extended to support Winscard drivers • Fuzz the windows drivers on linux without all the overhead DEF CON 2018 25 / 30
- 26. Smartcard fuzzing • Released now! • https://github.com/x41sec/x41- smartcard-fuzzing DEF CON 2018 26 / 30
- 27. pam_pkcs11: Replay an Authentication PAM Smartcard CRLServer GetCerti cates Certi cate Validate Certi cate and User RevocationCheck CRL RequestRandomNonce Nonce SignRequestforNonce Signature CheckSignatureAgainstCerti cate DEF CON 2018 27 / 30
- 28. Roadblocks • Channel back to card is quite limited • Might need to use revocation list check for information leaks • Interaction during exploitation not possible with basiccard, get SIMtrace for that • But: A single bitflip from false to true during login can be enough :) DEF CON 2018 28 / 30
- 29. Takeaways / Conclusions • Think about trust models! • Some security measures increase your attack surface big time! • Fuzz Everything! • Limit attack surface by disabling certain drivers. • Do not write drivers in C ;-) DEF CON 2018 29 / 30
- 30. Thanks • Q & A • https://github.com/x41sec/x41-smartcard- fuzzing • [email protected] • Sorry no Twitter... stalk me on LinkedIn if you must ;-) https://www.x41-dsec.de/ 30 / 30