如何判断当前LINUX系统启用了ASLR

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0

关闭ASLR

1

mmap base、stack、vdso page将随机化。这意味着.so文件将被加载到随机地址。链接时指定了-pie选项的可执行程序，其代码段加载地址将被随机化。配置内核时如果指定了CONFIG_COMPAT_BRK，randomize_va_space缺省为1。此时heap没有随机化。

2

在1的基础上增加了heap随机化。配置内核时如果禁用CONFIG_COMPAT_BRK，randomize_va_space缺省为2。

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查询randomize_va_space当前设置:

# sysctl -n kernel.randomize_va_space

1

# cat /proc/sys/kernel/randomize_va_space

1

关闭ASLR:

# sysctl -w kernel.randomize_va_space=0

# echo 0 > /proc/sys/kernel/randomize_va_space

（2）可以用ldd快速判断当前系统是否启用了ASLR:

$ ldd `which col`

        linux-gate.so.1 =>  (0xffffe000)

        libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7ded000)

        /lib/ld-linux.so.2 (0x80000000)

$ ldd `which col`

        linux-gate.so.1 =>  (0xffffe000)

        libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7db5000)

        /lib/ld-linux.so.2 (0x80000000)

$ ldd `which col`

        linux-gate.so.1 =>  (0xffffe000)

        libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7db0000)

        /lib/ld-linux.so.2 (0x80000000)

 

注意，本例中有两个so的加载基址未被随机化。

 

 

 

$ cat /proc/self/maps > 1.txt

$ cat /proc/self/maps > 2.txt

$ diff 1.txt 2.txt

4,15c4,15

< b7bb1000-b7db1000 r--p 00000000 08:01 98130      /usr/lib/locale/locale-archive

< b7db1000-b7db2000 rw-p b7db1000 00:00 0
< b7db2000-b7ef2000 r-xp 00000000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

< b7ef2000-b7ef4000 r--p 0013f000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

< b7ef4000-b7ef5000 rw-p 00141000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

< b7ef5000-b7ef8000 rw-p b7ef5000 00:00 0
< b7f09000-b7f0b000 rw-p b7f09000 00:00 0
< b7f0b000-b7f0c000 r-xp b7f0b000 00:00 0          [vdso]

< b7f0c000-b7f27000 r-xp 00000000 08:01 1046552    /lib/ld-2.11.2.so

< b7f27000-b7f28000 r--p 0001a000 08:01 1046552    /lib/ld-2.11.2.so

< b7f28000-b7f29000 rw-p 0001b000 08:01 1046552    /lib/ld-2.11.2.so

< bfe27000-bfe3d000 rw-p bfe27000 00:00 0          [stack]

---

> b7bfa000-b7dfa000 r--p 00000000 08:01 98130      /usr/lib/locale/locale-archive

> b7dfa000-b7dfb000 rw-p b7dfa000 00:00 0
> b7dfb000-b7f3b000 r-xp 00000000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

> b7f3b000-b7f3d000 r--p 0013f000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

> b7f3d000-b7f3e000 rw-p 00141000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

> b7f3e000-b7f41000 rw-p b7f3e000 00:00 0
> b7f52000-b7f54000 rw-p b7f52000 00:00 0
> b7f54000-b7f55000 r-xp b7f54000 00:00 0          [vdso]

> b7f55000-b7f70000 r-xp 00000000 08:01 1046552    /lib/ld-2.11.2.so

> b7f70000-b7f71000 r--p 0001a000 08:01 1046552    /lib/ld-2.11.2.so

> b7f71000-b7f72000 rw-p 0001b000 08:01 1046552    /lib/ld-2.11.2.so

> bfa6e000-bfa83000 rw-p bfa6e000 00:00 0          [stack]

 

diff输出表明stack、vsdo page、一些so的地址均被随机化。

 

$ cat 1.txt

08048000-0804f000 r-xp 00000000 08:01 196226     /bin/cat

0804f000-08050000 rw-p 00006000 08:01 196226     /bin/cat

08050000-08071000 rw-p 08050000 00:00 0          [heap]

b7bb1000-b7db1000 r--p 00000000 08:01 98130      /usr/lib/locale/locale-archive

b7db1000-b7db2000 rw-p b7db1000 00:00 0
b7db2000-b7ef2000 r-xp 00000000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

b7ef2000-b7ef4000 r--p 0013f000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

b7ef4000-b7ef5000 rw-p 00141000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

b7ef5000-b7ef8000 rw-p b7ef5000 00:00 0
b7f09000-b7f0b000 rw-p b7f09000 00:00 0
b7f0b000-b7f0c000 r-xp b7f0b000 00:00 0          [vdso]

b7f0c000-b7f27000 r-xp 00000000 08:01 1046552    /lib/ld-2.11.2.so

b7f27000-b7f28000 r--p 0001a000 08:01 1046552    /lib/ld-2.11.2.so

b7f28000-b7f29000 rw-p 0001b000 08:01 1046552    /lib/ld-2.11.2.so

bfe27000-bfe3d000 rw-p bfe27000 00:00 0          [stack]

$ cat 2.txt

08048000-0804f000 r-xp 00000000 08:01 196226     /bin/cat

0804f000-08050000 rw-p 00006000 08:01 196226     /bin/cat

08050000-08071000 rw-p 08050000 00:00 0          [heap]

b7bfa000-b7dfa000 r--p 00000000 08:01 98130      /usr/lib/locale/locale-archive

b7dfa000-b7dfb000 rw-p b7dfa000 00:00 0
b7dfb000-b7f3b000 r-xp 00000000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

b7f3b000-b7f3d000 r--p 0013f000 08:01 769046     /lib/i686/cmov/libc-2.11.2.so

b7f3d000-b7f3e000 rw-p 00141000 08:01 769046