Security
On Unix, a setuid program is given an environment chosen by its caller, but it runs with different authority from its caller. The dynamic linker will usually load code from locations specified by the environment variables LD_LIBRARY_PATH and LD_PRELOAD and run it with the process's authority. If a setuid program did this, it would be insecure, because its caller could get it to run arbitrary code and hence misuse its authority. For this reason, libc unsets these environment variables at startup in a setuid process. setuid programs usually unset unknown environment variables and check others or set them to reasonable values.
Read more about this topic: Environment Variable
Famous quotes containing the word security:
“...I lost myself in my work and never felt that marriage would give me the security I wanted. I thought that through the trade union movement we working women could get better conditions and security of mind.”
—Mary Anderson (1872–1964)
“It is hard for those who have never known persecution,
And who have never known a Christian,
To believe these tales of Christian persecution.
It is hard for those who live near a Bank
To doubt the security of their money.”
—T.S. (Thomas Stearns)
“To have in general but little feeling, seems to be the only security against feeling too much on any particular occasion.”
—George Eliot [Mary Ann (or Marian)