Linux

ASLR (Address Space Layout Randomization)

Description: ASLR randomly arrages the address space positions of key data areas of a process,including the base of the executeable and the positions of the stack, heap and libraries.

Check Status: cat /proc/sys/kernel/randomize_va_space

Enable: sudo sysctl -w kernel.randomize_va_space=2

Value:

  • 0: Disabled
  • 1: Partial (randomizes stack, mmap regions, but not heap)
  • 2: Full (randomizes all regions)

More Information: WikiPedia

Stack Canary

Description: Canaries or canary or stack cookies are know value that are placed between a buffer and control data on the stack to monitor buffer overflows.

Enable: GCC compilation flags

  • -fstack-protector: Protects some functions
  • -fstack-protector-all: Protects all functions
  • -fstack-protector-strong: Smart protects strategy

Value:

[TODO]: Determine the function at different levels.

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NX (No-Execute)

Description: NX is used to prevent certain types of malicious software form taking over computers by inserting their code into another program’s data storage area and running their code from within this section.

Check Status: grep nx /proc/cpuinfo to check if “nx” in the flags option. grep stack /proc/self/maps to check if “x” is exists.

Enable: Usually enabled at compile time with -z noexecstack

Value: GCC compilation flag: -Wl,-z,noexecstack

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PIE (Position Indepent Executable)

Description: PIE are executeable binaries made entirely from position-independent code. PIE are used in some security-focused Linux distributions to allow PaX or Exec Sheild to ues address space layout randomization to prevent attackers knowing where existing executable code in during a secrity attack using exploites that rely on knowing the offset of the executable code in the binray, sucn an return-to-libc attacks.

Check status: readelf -h <binray> | grep "Type"(should who “DYN”)

Enable: GCC compliation flags: -fpie -pie

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