Secure Software Development: Access Control and Information Leakage, Slides of Software Engineering

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Secure Software Development

Store and Protect Data Securely

Information Leakage

Error Handling Docsity.com

Information Protection

 During transit

 During use

 During storage

Access Control Requirement

• Cannot be bypassed
• Enforce least-privilege and need-to-know

restrictions

• Enforce organizational policy

Access Control

 Access control : ensures that all direct accesses to

object are authorized

 Protects against accidental and malicious threats

by regulating the reading, writing and execution of data and programs

 Need:

• Proper user identification and authentication
• Information specifying the access rights is protected form modification

Discretionary Access Control

• Access control is based on
  • User’s identity and
  • Access control rules
• Most common administration: owner based
  • Users can protect what they own
  • Owner may grant access to others
  • Owner may define the type of access given to others

Software and ACL

• Vulnerable languages: any
  • C, C++, Java, .Net, etc.
• Vulnerable platforms: any
  • Windows, UNIX, Linux, etc.

Recommendation

• Use the operating system’s security

technologies

• Keep secrets out of harm’s way
• Use security technology (access control

support, encryption, etc.) properly

• Scrub the memory securely once finished with

secret data

Weak Access Control

• Set access control and grants write access to low

privileged user

• Creates an object without setting access control and

creates object in a place writable by low-privileged user

• Writes configuration information into a shared area
• Writes sensitive information into a shared area

Problem Areas

• Embedding secret in code
  • Application code contains authentication, encryption keys, etc.

Information Leakage

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Communication Channels

 Overt Channel : designed into a system and documented in the user's manual

• Information leakage: designers and developers DO NOT understand security needs of the application

 Covert Channel : not documented. Covert channels may be deliberately inserted into a system, but most such channels are accidents of the system design.

• Information leakage: slow information flow to unauthorized recipient

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Information Flow

 Direct Flow:

• Bell-LaPadula example

 Indirect flow:

• Covert channel
• Inference channel

TS-subject

S-object

read info- flow

TS-object

S-subject

write info- flow

OTHER WAYS OF INFORMATION

LEAKAGE

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Yielding Too Much Information

 Error message carries information that can

be misused by the attacker

 Avoid: do not tell the user why his input

failed

 Problem: reduces usability