On the Practicability of Cold Boot Attacks

Transcription

1 On the Practicability of Cold Boot Attacks Michael Gruhn and Tilo Müller Friedrich-Alexander-University Erlangen-Nuremberg 2013/09/06 Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 1 / 23

2 Outline 1 Introduction RAM Remanence Cold boot attacks Motivation 2 Experiments Setup Results 3 Bypassing software countermeasures 4 Conclusions and Future Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 2 / 23

3 RAM Remanence How DRAM works DRAM consists of multiple capacitors Each capacitor s voltage represents bit state I over 50% charge = ˆ 1 bit / under 50% charge = ˆ 0 bit Voltage in a capacitor decays exponentially over time Memory controller constantly recharges capacitors RAM Remanence Decay significantly longer than time between RAM refreshes Decay so long RAM residue observable after cold/hard reboot Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 3 / 23

4 RAM Remanence How DRAM works DRAM consists of multiple capacitors Each capacitor s voltage represents bit state I over 50% charge = ˆ 1 bit / under 50% charge = ˆ 0 bit Voltage in a capacitor decays exponentially over time Memory controller constantly recharges capacitors RAM Remanence Decay significantly longer than time between RAM refreshes Decay so long RAM residue observable after cold/hard reboot Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 3 / 23

5 Cold boot attacks Cold boot attack Attacker uses RAM remanence to obtain RAM contents Attack procedure 1 Get physical access to victim s computer... either running, locked or suspended to RAM 2 Reboot computer into own OS 3 Read residual RAM content Assets FDE keys Any confidential data in RAM Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 4 / 23

6 Cold boot attacks Cold boot attack Attacker uses RAM remanence to obtain RAM contents Attack procedure 1 Get physical access to victim s computer... either running, locked or suspended to RAM 2 Reboot computer into own OS 3 Read residual RAM content Assets FDE keys Any confidential data in RAM Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 4 / 23

7 Cold boot attacks Cold boot attack Attacker uses RAM remanence to obtain RAM contents Attack procedure 1 Get physical access to victim s computer... either running, locked or suspended to RAM 2 Reboot computer into own OS 3 Read residual RAM content Assets FDE keys Any confidential data in RAM Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 4 / 23

8 Motivation Related work "Least we remember" Halderman et. al. "Bootjacker" Chan et. al. "Cold boot key recovery by solving [...]" Albrecht und Cid "[...] Approach to Recovering Noisy RSA Keys" Paterson et. al... Only "Least we remember" includes practical experiments "Least we remember" Halderman et. al. Never independently verified (to our knowledge) Does not test current DDR3 RAM Unclear how temperature was measured... Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 5 / 23

9 Motivation Related work "Least we remember" Halderman et. al. "Bootjacker" Chan et. al. "Cold boot key recovery by solving [...]" Albrecht und Cid "[...] Approach to Recovering Noisy RSA Keys" Paterson et. al... Only "Least we remember" includes practical experiments "Least we remember" Halderman et. al. Never independently verified (to our knowledge) Does not test current DDR3 RAM Unclear how temperature was measured... Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 5 / 23

10 Outline 1 Introduction RAM Remanence Cold boot attacks Motivation 2 Experiments Setup Results 3 Bypassing software countermeasures 4 Conclusions and Future Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 6 / 23

11 Tools Tools used during the experiments Thermometer Cooling Timing Sinometer DT8380 CRC Kontakt Chemie KÄLTE 75 SUPER SILVA STARTER digital stop watch Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 7 / 23

12 Cold boot attack experiment structure #1 Power up/boot #3 Cool RAM to c C Placement: for(i=0; i < N; i++) { RAM[i] = TESTDATA[i]; } WRITE_BACK_CACHES(); #2 Place test data #4 Shut down Cooling: C(c, t) #5 Wait t 1 Analysis: #6 Power up/boot Extraction: for(i=0; i < N; i++) { DUMP[i] = RAM[i]; } #7 Extract Remanence BIT_ERROR_COUNT = 0; for(i=0; i < N; i++) { #8 Analyze Remanence if( DUMP[i]!= TESTDATA[i] ) { BIT_ERROR_COUNT += POPCOUNT(DUMP[i] ^ TESTDATA[i]); } } 1 Optionally move RAM module to a different computer. Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 8 / 23

13 Execution Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 9 / 23

14 Outline 1 Introduction RAM Remanence Cold boot attacks Motivation 2 Experiments Setup Results 3 Bypassing software countermeasures 4 Conclusions and Future Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 10 / 23

15 Are cold boot attacks possible? YES, cold boot attacks are possible. What RAM remanence behaviour could be observed? DDR type RAM remanence observable after a cold reboot warm reset without cooling with cooling 1 Yes 1 No (reset) 2 Yes 2 Yes No Yes 2 No (reset) 3 Yes No (noise pattern) However, we could not exploit DDR3 RAM in cold reboot Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 11 / 23

16 Are cold boot attacks possible? YES, cold boot attacks are possible. What RAM remanence behaviour could be observed? DDR type RAM remanence observable after a cold reboot warm reset without cooling with cooling 1 Yes 1 No (reset) 2 Yes 2 Yes No Yes 2 No (reset) 3 Yes No (noise pattern) However, we could not exploit DDR3 RAM in cold reboot Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 11 / 23

17 Noise patterns in DDR3 systems after a cold reboot Noise different after each reboot This could either be caused by I I the memory controller intrinsic property of DDR3 Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 12 / 23

18 Does cooling really prolong RAM remanence? Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 13 / 23

19 Does cooling really prolong RAM remanence?: YES Asus Eee PC 1010H with a NT512T64UH8A1FN-3C 512 MiB DDR2 module C 8-11 C C Correct bits (%) Time (s) Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 14 / 23

20 Does cooling really prolong RAM remanence?: YES Asus Eee PC 1010H with a HYMP512S64BP8-Y5 1024MiB DDR2 module C 8-12 C C Correct bits (%) Time (s) Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 15 / 23

21 Can cooled RAM be transplanted? Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 16 / 23

22 Can cooled RAM be transplanted? YES, RAM transplantation is possible. However, the RAM controllers must be compatible Errors for transplantation from Asus Eee PC 1010H to Asus Eee PC 1010H Temperature ( C) Errors (bits) Correct bits (%) Errors low enough for key recovery Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 17 / 23

23 Outline 1 Introduction RAM Remanence Cold boot attacks Motivation 2 Experiments Setup Results 3 Bypassing software countermeasures 4 Conclusions and Future Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 18 / 23

24 Bypassing software countermeasures What mitigation can be bypassed? RAM reset on boot: YES, via RAM transplantation Locked boot process: YES, via RAM transplantation Temperature detection: YES, via non-cooled RAM transplantation 0x7c00 defense: THEORETICALLY, via RAM transplantation Use a two RAM slot machine Transplant victim s RAM into higher address space slot Not practically verified... yet All software countermeasures can be bypassed, because once the RAM is removed it is out of reach of software. Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 19 / 23

25 Bypassing software countermeasures What mitigation can be bypassed? RAM reset on boot: YES, via RAM transplantation Locked boot process: YES, via RAM transplantation Temperature detection: YES, via non-cooled RAM transplantation 0x7c00 defense: THEORETICALLY, via RAM transplantation Use a two RAM slot machine Transplant victim s RAM into higher address space slot Not practically verified... yet All software countermeasures can be bypassed, because once the RAM is removed it is out of reach of software. Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 19 / 23

26 Outline 1 Introduction RAM Remanence Cold boot attacks Motivation 2 Experiments Setup Results 3 Bypassing software countermeasures 4 Conclusions and Future Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 20 / 23

27 Conclusions and future work Conclusions Halderman et al. practically verified Software countermeasures are bypassed via RAM transplantation RAM is unsecure storage DDR3 RAM seems to stop practical cold boot attacks Future work More research to proof inability to exploit DDR3-technology How to sufficiently proof DDR3 not exploitable testing all machines is not practical deeper electrical engineering knowledge of DDR3 needed Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 21 / 23

28 Conclusions and future work Conclusions Halderman et al. practically verified Software countermeasures are bypassed via RAM transplantation RAM is unsecure storage DDR3 RAM seems to stop practical cold boot attacks Future work More research to proof inability to exploit DDR3-technology How to sufficiently proof DDR3 not exploitable testing all machines is not practical deeper electrical engineering knowledge of DDR3 needed Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 21 / 23

29 Questions? 42 Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 22 / 23

30 Questions? PAQ Why did you only test 5 DDR3 machines? No budget University s master agreement on computer hardware Have you contacted Halderman et al. at all? There was unfortunately no time for that Where is that "signature" on system M coming from? We don t know Maybe BIOS probing the RAM Maybe you caused the "signature" by error in your tools? Tested with 2 independently developed tools If we place known data then acquire that it is fine "Signature" only present on one machine Michael Gruhn, Tilo Müller (FAU) On the Practicability of Cold Boot Attacks 2013/09/06 23 / 23