Security and Web Programming/Design
cell phones bio-facilities Sodas, junk food, and coffee Welcome to the No Smoking State
who are you? where are you from? what do you do? Emacs or vi?
Warm Fuzzies Secure Design and Implementation Wordage
Security Concepts Vetting Software Design Strategy Developer practices Coding Practices Operational Practices
Security Concepts
trust transitive trust
principle of least privilege enumerating badness “best block: not be there” -- Mr. Miyage
“defense in depth”
threats vulnerabilities risks
who accepts the risk?
being paranoid
confidentiality integrity availability
protect what you can detect what you can’t prevent
hammers, nails...
a security mechanism is design to protect against a specific finite set of attacks. It usually fails gloriously when modified or used for other purposes.
don’t design your own new security protocol
the law of unintended consequences
don’t rely on the environment for protection don’t rely on good behavior don’t rely on things you can’t control
how apache.org got pwn3d
ftproot == wwwroot webuser == o+w
upload php via ftp upload backdoor code compile and execute via http c+-o+httpd+httpd.c voila! shell on web server
bugzilla talking to mysql mysql running as root mysql username/password stored script
create table with text field insert: #!/bin/sh cp /bin/sh /tmp/.rootsh chmod 4755 /tmp/.rootsh rm -f /root/.tcshrc query: SELECT... INTO ‘/root/.tchsrc’ wait for someone to “su -”
Security Vetting
What is it supposed to do? How does it work? What side effects are there? How is it deployed and maintained?
How does it fail? What is the risk? Can it be mitigated?
usability and security
understanding caring under-budget
security is an enabling task
It is especially important for expert programmers to internalize this habit, for two reasons. One is that expert programmers are disproportionately drawn from the high end of the bell curve in their working-set size; therefore they tend to systematically overestimate the amount of complexity other people can handle easily. -- Eric S. Raymond, The Art of Unix Usability
Design Strategy
top down design
goals requirements design review
what is the end result? what problem trying to solve? *not* how it is implemented
security usability performance environmental
support deployment political external
as simple as possible to meet the requirements add requirements if apparent during design be prepared to change when requirements can’t be met
for each security control what threat is addressed? Really?
recent examples
Developer Practices
The three virtues of a programmer are laziness, impatience, and hubris. -- Larry Wall
Group permissions and accounts Code Safety Test Environment Regression Testing
Coding Practices
bounds checking input validation no client-side trust error checking
sql injection cross-site scripting credential handling data mapping logging
don’t require shell for remote execution
Operational Practices
Server accounts and permissions handling credentials accountability software maintenance documentation testing and debugging