JETPLOW is dead. Long live the JETPLOW!

Documents on NSA software published by Edward Snowden created a stir, but did not allow seeing how it actually worked. That came possible after the Shadow Brokers’ leakage was published. We were not idling during that period and attempted to replicate that work through our independent research. In this report, we will deeply analyze the leaked JETPLOW and compare it against our own results. We will also think about how this situation and such backdoors can be developed further on, and how things stand with other equipment from Cisco. In the last part we will show methods for detecting such backdoors.

Transcript

1. JETPLOW is dead. Long live the JETPLOW! Roman Bazhin @nezlooy Maxim Malyutin @jesusfailed
2. Team lead and security researcher at Digital Security r.bazhin@dsec.ru @nezlooy Traineeship Program: traineeship@dsec.ru #whoami 2
3. • Intro • Cisco ASA 5525-X • Internals • Implantation • JETPLOW • Cisco Catalyst 3850 • Internals • Implantation • Summary Agenda 3
5. Cisco ASA 5525-X Intro 5
6. NSA Ant Product Catalog Intro 6
7. NSA Ant Product Catalog / Restrictions Intro 7
8. Why is it so interesting? Intro 8
9. Why is it so interesting? Intro 9
10. Internals / Flash Сhips Cisco ASA 5525-X BIOS Flash NAND (boot:) 10
11. Internals / Booting Cisco ASA 5525-X * v. 9B2C109A * 11
12. Internals / Boot images Cisco ASA 5525-X 12
13. 1. | asa823-k8 | 0x100000 | 2.6.29.6 | 2010-08-06 13:51:46 2. | asa824-1-k8 | 0x100000 | 2.6.29.6 | 2010-12-18 00:02:38 ... | | | | 13. | asa825-smp-k8 | 0x200000 | 2.6.29.6 | 2011-05-20 23:33:17 ... | | | | 119. | asa932-2-smp-k8 | 0x1000000 | 3.10.19-WR6.0.0.2_standard | 2015-01-28 23:27:02 ... | | | | 122. | asa933-smp-k8 | 0x1000000 | 3.10.19-WR6.0.0.2_standard | 2015-04-22 16:35:34 123. | asa941-1-smp-k8 | 0x1000000 | 3.10.55-ltsi-WR6.0.0.13_standard | 2015-05-05 03:47:13 ... | | | | 142. | asa962-smp-k8 | 0x1000000 | 3.10.62-ltsi-WR6.0.0.27_standard | 2016-08-24 01:42:33 Internals / Boot images / Timeline Cisco ASA 5525-X 13
14. • No sign • The image can be reassembled with recalculation of hash • Hash is stored in the "BootLdr“ header (either md5, sha1, sha512) • You can build your own boot image • 0x14000 <- ROMMON TFTP Loader • 0x100000 <- ROMMON GRUB • Easily boot with Nintendo emulator Internals / Bringing arbitrary code / Custom boot images Cisco ASA 5525-X 14
15. • No sign • The image can be reassembled with recalculation of hash • Hash is stored in the "BootLdr“ header (either md5, sha1, sha512) • You can build your own boot image • 0x14000 <- ROMMON TFTP Loader • 0x100000 <- ROMMON GRUB • Easily boot with Nintendo emulator Internals / Bringing arbitrary code / Custom boot images Cisco ASA 5525-X 15
16. Internals / BIOS Flash Map Cisco ASA 5525-X 16
17. Internals / BIOS Flash Map / BIOS WE Cisco ASA 5525-X BIOS Write Enable (BIOSWE) 0 = Only read cycles result in Firmware Hub I/F cycles. 1 = Access to the BIOS space is enabled for both read and write cycles. When this bit is written from a 0 to a 1 and BIOS Lock Enable (BLE) is also set, an SMI# is generated. This ensures that only SMI code can update BIOS. BIOS Lock Enable (BLE) 0 = Setting the BIOSWE will not cause SMIs. 1 = Enables setting the BIOSWE bit to cause SMIs. Once set, this bit can only be cleared by a PLTRST# http://www.intel.com/content/dam/doc/datasheet/io-controller-hub-9-datasheet.pdf 17
18. Internals / BIOS Flash Map / UEFI Tool Cisco ASA 5525-X https://github.com/LongSoft/UEFITool 18
19. Safety rules Cisco ASA 5525-X BIOS Flash 19
20. Safety rules / Ignored Cisco ASA 5525-X 20
21. Implantation / Version 1 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 21
22. Implantation / Version 1 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 22
23. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 23
24. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 24
25. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 25
26. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina 26
27. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina ??? 27
28. Implantation / Version 2 Cisco ASA 5525-X FirstLdr SecondLdr BootLdr Vmlinuz Rootfs ROMMON GRUB StubLdr startup Vmlinux do_execve lina SMM 28
29. Implantation / Version 2 / Software SMI# Timer Cisco ASA 5525-X Software SMI# Timer Enable (SWSMI_TMR_EN) 0 = Disable. Clearing the SWSMI_TMR_EN bit before the timer expires will reset the timer and the SMI# will not be generated. 1 = Starts Software SMI# Timer. When the SWSMI timer expires (the timeout period depends upon the SWSMI_RATE_SEL bit setting), SWSMI_TMR_STS is set and an SMI# is generated. SWSMI_TMR_EN stays set until cleared by software. Software SMI# Timer Rate Selector (SWSMI_RATE_SEL) 00 = 1.5 ms ± 0.6 ms 01 = 16 ms ± 4 ms 10 = 32 ms ± 4 ms 11 = 64 ms ± 4 ms http://www.intel.com/content/dam/doc/datasheet/io-controller-hub-9-datasheet.pdf 29
30. void __fastcall SMIFlashSMIHandler(void *DispatchHandle, EFI_SMM_SW_DISPATCH_CONTEXT *DispatchContext) { /* ... */ SwSmiInputValue = DispatchContext->SwSmiInputValue; CpuSaveStateOffset = 0x2C8 * Cpu; LowBufferAddress = *(CpuSaveStateOffset + v9 + offsetof(EFI_SMM_CPU_STATE32, _EBX)); HighBufferAddress = Shl64(*(CpuSaveStateOffset + v9 + offsetof(EFI_SMM_CPU_STATE32, _ECX)), 32); v14 = (SwSmiInputValue - 0x20); pCommBuff = (LowBufferAddress + HighBufferAddress); switch (SwSmiInputValue) { /* ... */ case 0x21: ReadFlash(pCommBuff); break; /* ... */ } /* ... */ } Implantation / Version 2 / SMM / SMIFlash Cisco ASA 5525-X 30
31. void __fastcall SMIFlashSMIHandler(void *DispatchHandle, EFI_SMM_SW_DISPATCH_CONTEXT *DispatchContext) { /* ... */ SwSmiInputValue = DispatchContext->SwSmiInputValue; CpuSaveStateOffset = 0x2C8 * Cpu; LowBufferAddress = *(CpuSaveStateOffset + v9 + offsetof(EFI_SMM_CPU_STATE32, _EBX)); HighBufferAddress = Shl64(*(CpuSaveStateOffset + v9 + offsetof(EFI_SMM_CPU_STATE32, _ECX)), 32); v14 = (SwSmiInputValue - 0x20); pCommBuff = (LowBufferAddress + HighBufferAddress); switch (SwSmiInputValue) { /* ... */ case 0x21: ReadFlash(pCommBuff); break; /* ... */ } /* ... */ } Implantation / Version 2 / SMM / SMIFlash Cisco ASA 5525-X 31
32. ; __int64 __fastcall ReadFlash(FUNC_BLOCK *pFuncBlock) ReadFlash proc near mov edx, [rcx+FUNC_BLOCK.BlockAddr] mov r8, [rcx+FUNC_BLOCK.BufAddr] xor r9d, r9d add edx, 0FFC00000h cmp [rcx+FUNC_BLOCK.BufSize], r9d jbe short loc_4003F3 loc_4003DD: mov al, [rdx] inc r9 inc rdx mov [r8], al mov eax, [rcx+FUNC_BLOCK.BufSize] inc r8 cmp r9, rax jb short loc_4003DD loc_4003F3: mov [rcx+FUNC_BLOCK.ErrorCode], 0 xor eax, eax retn ReadFlash endp Implantation / Version 2 / SMM /SMIFlash.ReadFlash Cisco ASA 5525-X 32
33. ; __int64 __fastcall ReadFlash(FUNC_BLOCK *pFuncBlock) ReadFlash proc near mov edx, [rcx+FUNC_BLOCK.BlockAddr] mov r8, [rcx+FUNC_BLOCK.BufAddr] xor r9d, r9d add edx, 0FFC00000h ; Integer Overflow here cmp [rcx+FUNC_BLOCK.BufSize], r9d jbe short loc_4003F3 loc_4003DD: mov al, [rdx] inc r9 inc rdx mov [r8], al mov eax, [rcx+FUNC_BLOCK.BufSize] inc r8 cmp r9, rax jb short loc_4003DD loc_4003F3: mov [rcx+FUNC_BLOCK.ErrorCode], 0 xor eax, eax retn ReadFlash endp Implantation / Version 2 / SMM /SMIFlash.ReadFlash Cisco ASA 5525-X 33
34. ; __int64 __fastcall ReadFlash(FUNC_BLOCK *pFuncBlock) ReadFlash proc near mov edx, [rcx+FUNC_BLOCK.BlockAddr] mov r8, [rcx+FUNC_BLOCK.BufAddr] xor r9d, r9d add edx, 0FFC00000h ; Integer Overflow here cmp [rcx+FUNC_BLOCK.BufSize], r9d jbe short loc_4003F3 loc_4003DD: mov al, [rdx] inc r9 inc rdx mov [r8], al mov eax, [rcx+FUNC_BLOCK.BufSize] inc r8 cmp r9, rax jb short loc_4003DD loc_4003F3: mov [rcx+FUNC_BLOCK.ErrorCode], 0 xor eax, eax retn ReadFlash endp Implantation / Version 2 / SMM /SMIFlash.ReadFlash Cisco ASA 5525-X Lenovo Security Advisory: LEN-4710 https://support.lenovo.com/us/en/product_security/len_4710 34
35. Stage 1  Relocate from BIOS Flash to RAM Stage 2  Relocate from RAM to SMRAM Stage 3  Decrypt next stages Stage 4  Wipe used stages from RAM to hide the traces  SMM Timer  Check StubLdr  Extract Vmlinuz  Parser ELF and collect symbols  Wait kernel  Allocate dropper  Splice function `open_exec` Implantation / Version 2 / Stages Cisco ASA 5525-X Stage 5  Dropper Stage 6  Shim Stage 7  Payload 35
36. • Boot with custom evil image (local, remote and etc.)* • Examine platform configuration • Pass collected info back to attacker e.g. via SSH connection • Build stages • Infect • Cleanup • Reload the platform * PIC Implantation / Version 2 / Infection Cisco ASA 5525-X 36
37. Implantation / Version 2 / After infection Cisco ASA 5525-X 37
38. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L ROMMON GRUB 38
39. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L ROMMON GRUB Stage 2 39
40. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L ROMMON GRUB Stage 2 Stage 3 40
41. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 2 Stage 3 Stage 4 ROMMON GRUB 41
42. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 2 Stage 3 Stage 4 ROMMON GRUB 42
43. Stage 4 Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L ROMMON GRUB BootLdr 43
44. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 BootLdr StubLdr 44
45. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 BootLdr StubLdr 45 Extracted copy of linux kernel
46. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 BootLdr StubLdr Linux kernel 46
47. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 StubLdr Linux kernel 47 BootLdr
48. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Linux kernel 48 Stage 4
49. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Linux kernel Stage 5 49 Stage 4
50. Linux kernel Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 Stage 5 Linux kernel 50
51. Linux kernel Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 4 Stage 5 Stage 6 Linux kernel 51
52. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 6 Linux kernel Stage 7 52
53. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 6 Linux kernel Stage 7 /asa/bin/lina 53
54. Implantation / Version 2 / Cruise control Cisco ASA 5525-X t SMM R/P/L Stage 6 Linux kernel Stage 7 /asa/bin/lina 54
55. The NSA Implant / If it quacks like a duck… JETPLOW 55
56. • BannanaDaiquiri 3.1.2* (BG3121) • ScreamingPlow 2.8 (SCP28) • Cisco ASA 5505 with ROMMON v. 10.0(12)13 • Boot image v. 8.3.1 (asa831-k8) • Custom evil engineering boot image The NSA Implant / Limitations of the research JETPLOW 56
57. • Assemble Keyed Flash Image for target • The image must be generated specifically for a target firewall with reference to some basic information about it (series, version ROMMON, etc.) • Load Keyed Flash Image and wait for remote connection • Customize the implant and start the infection process • Send implant to target • Install implant • Cleanup • Reload the platform The NSA Implant / Infection JETPLOW 57
58. <patch> <data src="inline" type="userarea">0</data> <!-- Assigned later --> <address>fff70000</address> <!-- SECOND_USER_AREA_ADDRESS --> </patch> <patch> <data src="file">bin/asa5505/SCP28/asa5505_patch60000.bin</data> <address>fff60000</address> <!-- FIRST_CODE_AREA_ADDRESS --> </patch> <patch> <data src="inline" type="pbd">0</data> <!-- Assigned later --> <address>fff6df00</address> <!-- FIRST_USER_AREA_ADDRESS --> </patch> <patch> <data src="file">bin/asa5505/SCP28/asa5505_patchEC480.bin</data> <address>fffec480</address> <!-- SECOND_CODE_AREA_ADDRESS --> </patch> <patch> <data src="file">bin/asa5505/SCP28/asa5505_patchE18BF.bin</data> <address>fffe18bf</address> <!-- HOOK_ADDRESS --> </patch> The NSA Implant / Configuring / “my hovercraft is full of eels” JETPLOW Part of decrypted “asa5505_101213_install_SCP28.pif” 58
59. ; ; --- SECTION I --- ; allocb 0x008d6e94 rand 0x00b978c0 freeb 0x008d7280 process_create 0x0010dbec open 0x00110368 process_suspend 0x0010ea9c ip_put 0x0047f670 process_sleep_for 0x0010f4e0 close 0x0011046c show_process 0x006f8ab0 atoip 0x00b8d928 cur_t 0x00db4510 memset 0x00b7b1d8 calc_ip_cksum 0x00482ea4 memmove 0x00b97a6c arp_loopkup 0x00484664 malloc_call_calloc 0x008d6b70 send_it 0x00481604 free 0x00b8319c arp_create 0x00486784 printf 0x0010fc70 get_hw_iface_2 0x0074148c ... ... ... ... The NSA Implant JETPLOW Part of “40086100.dat” 59
60. ; ; --- SECTION II --- ; HookLocation 0x005f6425 FlashClassAddr 0x00000000 JmpLocation 0x005f90a6 CryptoDeviceAddr 0x00db7fd0 InterfaceAddr 0x00c866ac ArpTableAddrPtr 0x00c793a8 InterfaceLeng 0x000001b8 ArpTableLastPtr 0x00c793b0 IntSecurityOffset 0x1c NumInterfaces 0x00000000 IntNameOffset 0x188 IfaceStruct2 0x00000000 IntNumOffset 0x143 FlashFileInfoSizeOffset 0x00000018 IntVlanOffset 0x10 PIXFlashRmfileAddress 0x0035c30c IntIPOffset 0x20 FlashDirlistAddress 0x003e7b1c IntNetmaskOffset 0x24 FlashChmodAddress 0x003e7c40 ... ... ... ... The NSA Implant JETPLOW Part of “40086100.dat” 60
61. The NSA Implant / After infection / BIOS Flash Map JETPLOW 61
62. Implantation / Version 2 / Causes of SMI# Cisco ASA 5525-X http://opensecuritytraining.info/IntroBIOS_files/Day1_07_Advanced x86 - BIOS and SMM Internals - SMM.pdf 62
63. Second Code Area First Code Area Linux Kernel Lina The NSA Implant / IDT Trick 63
64. Second Code Area First Code Area Linux Kernel Lina The NSA Implant / IDT Trick 64
65. First Code Area Linux Kernel Lina Second Code Area The NSA Implant / IDT Trick 65
66. First Code Area Linux Kernel Lina Second Code Area The NSA Implant / IDT Trick 66
67. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 67
68. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 68
69. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 69
70. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 70
71. Second Code Area First Code Area Linux Kernel Lina The NSA Implant / IDT Trick 71
72. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 72
73. First Code Area Second Code Area Linux Kernel Lina The NSA Implant / IDT Trick 73
74. First Code Area Linux Kernel Lina Second Code Area The NSA Implant / IDT Trick 74
75. • After reverse JETPLOW, we can notice that: • The authors have done a awesome job; • Implant supports a wide range of various hardware (PIX 701 – ASA 5505); • Well thought-out architecture of the latest versions; • The industrial approach. • Further readings: • https://dsec.ru/ipm-research-center/research/architecture_jetplow/ The NSA Implant / Conclusion JETPLOW 75
76. • After reverse JETPLOW, we can notice that: • The authors have done a awesome job; • Implant supports a wide range of various hardware (PIX 701 – ASA 5505); • Well thought-out architecture of the latest versions; • The industrial approach. • Further readings: • https://dsec.ru/ipm-research-center/research/architecture_jetplow/ • JETPLOW feedback: • E-mail: nsapao@nsa.gov. Phone Number: +1-301-688-6524 The NSA Implant / Conclusion JETPLOW 76
77. • BIOS Stealth • Hook BIOS R/W-code (SMIFlash) • Use Flash SPI SMI# Enable (FSMIE)* to hook HW/SW sequencing access to BIOS Flash • Anti ROMMON upgrade • FS Stealth • Hook `filp_open` and `filp_write` in kernel mode • Hook `open`, `fopen`, `access`, `stat` etc. in user space • … Anti-forensic / “Check the logs on the ASA firewall” Cisco ASA 5525-X 77
78. • Potentially implantation may be subject to: • Cisco official position: > This list of ASA hardware models provided do not support secure boot or hardware-based attestation of a digitally signed image. > Your scenario where a custom image could be booted and made persistent might be possible on the ASA hardware platforms which do not support secure boot or hardware-based attestation. Conclusion / It's not a bug, it's an undocumented feature Cisco ASA 5525-X ASA 5505 ASA 5510 ASA 5512-X ASA 5515-X ASA 5520 ASA 5540 ASA 5545-X ASA 5550 ASA 5555-X ASA 5580 ASA 5585-X 78
79. Cisco 3850 79
80. Cisco 3850 Internals 80
81. Internals / Flash Сhips Cisco 3850 NOR Flash NAND (sda) 81
82. Internals / Booting Cisco 3850 Main process /usr/binos/bin/iosd RESET ROMMON SBL Linux Kernel Boot image on NAND Flash (boot:) NOR Flash FBL 0xBFC00000 0xBFC01000 0x80030000 0x80100000 82
83. Internals / Booting Cisco 3850 First Boot Loader (FBL): 1. RESET j start 2. init_boot_bus(), init_i2c_bus(), init_dram(), etc. 3. sw 0x0800C180 which translates to j sbl_entry @ 0x80030000 4. memcpy(sbl_entry + 4, sbl_text, …) 5. j sbl_entry Second Boot Loader (SBL): 6. expand_bundle(), verify_nova_pkg(), … 7. launch_kernel() 83
84. mtdparts=norda: 8m@0xbf40000(all) 1m@0(bs) 64k@0x100000(vb) 64k@0x110000(pb) 64k@0x120000(db) 6848k@0x130000(boot) 64k@0x7e0000(vb1) 64k@0x7f0000(rkey) Internals / NOR Flash Map Cisco 3850 84
85. Internals / Boot images Cisco 3850 Header TLVs Signature Packages Header TLVs Signature Files Type Length Value Offset Length Mode Name Bundle (.bin) Package TLV Types 22-25 85
86. Internals / Boot images Cisco 3850 Header TLVs Signature Packages Header TLVs Signature Files Type Length Value Offset Length Mode Name Bundle (.bin) Package TLV Types 22-25 Linux kernel Parts of file system 86
87. Internals / Bringing arbitrary code / Custom boot images Cisco 3850 Header TLVs Signature Packages Header TLVs Signature Files Type Length Value Offset Length Mode Name Bundle (.bin) Package TLV Types 22-25 Linux kernel Parts of file system 87
88. // /usr/bin/unbundle // ... snprintf(&fullpath, "%s/%s", tmpdir, pkgname); fd = fopen(fullpath, "wb"); fwrite(fd, 1, pkgsize, pkgdata); fclose(fd); chmod(fullpath, pkgaccess); // ... Internals / Bringing arbitrary code / Custom boot images Cisco 3850 88
89. // /usr/bin/unbundle // ... snprintf(&fullpath, "%s/%s", tmpdir, pkgname); fd = fopen(fullpath, "wb"); fwrite(fd, 1, pkgsize, pkgdata); fclose(fd); chmod(fullpath, pkgaccess); // ... Internals / Bringing arbitrary code / Custom boot images Cisco 3850 89
90. // /usr/bin/unbundle // ... snprintf(&fullpath, "%s/%s", tmpdir, pkgname); // ../../usr/bin/FILE fd = fopen(fullpath, "wb"); fwrite(fd, 1, pkgsize, pkgdata); fclose(fd); chmod(fullpath, pkgaccess); // ... Internals / Bringing arbitrary code / Custom boot images Cisco 3850 90
91. // /usr/bin/unbundle // ... snprintf(&fullpath, "%s/%s", tmpdir, pkgname); // ../../usr/bin/FILE fd = fopen(fullpath, "wb"); fwrite(fd, 1, pkgsize, pkgdata); fclose(fd); chmod(fullpath, pkgaccess); // ... Internals / Bringing arbitrary code / Custom boot images Cisco 3850 Cisco Security Advisory: cisco-sa-20161115-iosxe https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161115-iosxe 91
92. Switch# request system shell Are you sure you want to continue? [y/n] y Challenge: c804288d2b32cef958a77...skip...465f633d51aeb4702daf7166b Please enter the shell access response based on the above challenge (Press "Enter" when done or to quit.): Implantation / Infection Cisco 3850 92
93. Switch# request system shell Are you sure you want to continue? [y/n] y Challenge: c804288d2b32cef958a77...skip...465f633d51aeb4702daf7166b Please enter the shell access response based on the above challenge (Press "Enter" when done or to quit.): Implantation / Infection Cisco 3850 /usr/bin/code_sign_verify_nova_pkg 93
94. Switch# request system shell Are you sure you want to continue? [y/n] y Challenge: c804288d2b32cef958a77...skip...465f633d51aeb4702daf7166b Please enter the shell access response based on the above challenge (Press "Enter" when done or to quit.): Implantation / Infection Cisco 3850 /usr/bin/code_sign_verify_nova_pkg /bin/true 94
95. Switch> en Switch# software expand file flash/:CVE-2016-6450.bin Preparing expand operation ... [1]: Expanding bundle usbflash0:CVE-2016-6450.bin [1]: Copying package files [1]: Package files copied [1]: Finished expanding bundle usbflash0:CVE-2016-6450.bin Switch# conf t Switch(config)# service internal Switch(config)# end ... Internals / Bringing arbitrary code / Jailbreak Cisco 3850 95
96. ... Switch# request system shell Are you sure you want to continue? [y/n] y Challenge: c804288d2b32cef958a5a47377...skip...465f633d51aeb4702daf7166b Please enter the shell access response based on the above challenge (Press "Enter" when done or to quit.): SUPER-SECRET-ENGINEERING-PASSWORD ********************************************************************** Activity within this shell can jeopardize the functioning of the system. Use this functionality only under supervision of Cisco Support. Logging to media is disabled since the media device bootflash: is not available. ********************************************************************** Terminal type 'network' unknown. Assuming vt100 [linux:/]$ uname -a Linux linux 2.6.32.59-cavium-octeon2.cge-cavium-octeon #1 SMP PREEMPT Fri May 10 11:48:14 PDT 2013 mips64 GNU/Linux Internals / Bringing arbitrary code / Jailbreak Cisco 3850 96
97. • Jailbreak (local, remote and etc.)* • Examine platform configuration • Pass collected info back to attacker e.g. via SSH connection • Build stages • Infect • Cleanup • Reload the platform * PIC Implantation / Infection Cisco 3850 97
98. Implantation / Infection Cisco 3850 1. Patch sw 0x800C180 sw 0x8000004 Original: Patched: j sbl_start j s1_entry nop nop ... ... ; <- s1_entry ; @ 0xBFC14BF4 2. Store Stage 1 code just below j sbl_start start instruction 3. Store the rest of the implant in the free space at the end of the BS j sbl_start j s1_entry 98
99. mtdparts=norda: 8m@0xbf40000(all) 1m@0(bs) 64k@0x100000(vb) 64k@0x110000(pb) 64k@0x120000(db) 6848k@0x130000(boot) 64k@0x7e0000(vb1) 64k@0x7f0000(rkey) Implantation / NOR Flash Map / After infection Cisco 3850 99
100. • Stage 1 • Relocate Stage 2 code to RAM @ 0x80000000 • Splice launch_kernel() to take over control when the kernel code has been allocated • Stage 2 • Splice init_post() to take over control just before the kernel is ready to execute /sbin/init • Stage 3 • Use kmem_cache_alloc() to allocate memory for Stages 4 – 5 • Call kernel_thread() with threading procedure set to Stage 4 code • Stage 4 • Call kernel_execve() to move thread from kernel space to user space and run /bin/bash (which is Stage 5) • Stage 5 • bash –c eval “dd if=/dev/mtd0 of=/tmp/evil.so … && export LD_PRELOAD=/tmp/evil.so” Implantation / Cruise control Cisco 3850 100
101. • Anti-update • Hook `mtd_read` and `mtd_write` • Anti-logging • Hook `filp_open` and `filp_write` • … Anti-forensic Cisco 3850 101
102. • Potentially implantation may be subject to: • Cisco official position: > CVE-2016-6450 > Cisco IOS XE Software Directory Traversal Vulnerability > CVSS Score: Base 1.5, Temporal 1.2 • Little bit evil (up to 7.5) • Cisco Smart Install. Pentester’s opportunities Conclusion Cisco 3850 Cisco 5700 Series Wireless LAN Controllers Cisco Catalyst 4500E Series Switches Cisco Catalyst 4500X Series Switches Cisco Catalyst 3650 Series Switches 102
103. • Without hardware protection the bootkit development is not a rocket science; • Watch a defensive tool (like ASA firewall) become an offensive one; • Independent research; • More independent research; • Best practices just gives you an illusion of security. Summary 103
104. $$$ Mitigations 104
105. Thumbs up, reposts are welcome! Questions? 105