Notes - MCS
Identification, Authentication and Authorization
Notes - MCS
Identification, Authentication and Authorization
  • Identification, Authentication and Authorization
  • Access Control Models
    • Access types
    • Least privilege principle
    • Access control models
      • Access control kinds
    • Access control kinds
    • Separation of duties
    • Segregation of duties
    • Information flow models
    • Multilevel security
    • Windows mandatory integrity control
    • Clark-Wilson Integrity Model
  • OAuth 2.0 Authorization Framework
    • Goal
    • Roles (RFC 6749)
    • Communication endpoints
    • Application (client)
    • OAuth tokens
    • OAuth flows
      • Code flow
      • Implicit flow
      • Resource owner password flow
      • Client credentials flow
    • Proof Key for Code Exchange (PKCE, RFC 7636)
    • Device authorization grant (RFC 8628)
    • Actual protocol flow
  • Linux Security Mechanisms
    • Mechanisms
    • Linux management privileges
    • Privilege Elevation
    • Capabilities
    • Files extended attributes (xattr)
    • File capabilities
    • Capability transfer across exec
    • Control groups (cgroups)
    • Linux Security Modules (LSM)
    • AppArmor
    • Confinement
  • Authentication Protocols
    • Identity attributes
    • Authentication
    • Authentication interactions
    • Authentication of people
      • Biometrics
      • Token-based OTP generators
      • PAP & CHAP (RFC 1334, 1992, RFC 1994, 1996)
      • S/Key (RFC 2289, 1998)
      • GSM
    • Host authentication
    • Service/server authentication
    • TLS (Transport Layer Security, RFC 8446)
    • SSH (Secure Shell, RFC 4251)
    • Single Sign-On (SSO)
    • Authentication metaprotocols
    • Authentication services
    • Key distribution services
  • PAM (Pluggable Authentication Modules)
    • Motivation
    • PAM
    • PAM APIs
    • Orchestration of PAM actions
    • Module invocation
    • Configuration files
    • PAM orchestration files
    • Scenario 1 – Local authentication
    • Scenario 2 – LDAP auth with local backoff
    • Scenario 3 – MS AD auth with local backoff
  • FIDO and FIDO2 framework
    • FIDO (Fast Identity Online) Alliance
    • Universal 2nd Factor (U2F) protocol
    • WebAuthn
    • Client to Authenticator Protocol (CTAP)
    • Passkeys
  • Authentication with Trusted Third Parties / KDCs
    • Shared-key authentication
    • Key Distribution Center (KDC) concept
    • Kerberos
  • Identity Management
    • Digital Identity
    • Identity Manager (IdM)
    • Identity Provider (IdP)
    • Authoritative source
    • Identity claim
    • Approachs
    • Credential
    • Privacy issues
    • Verifiable credential (VC)
    • Self-Sovereign Identity (SSI)
    • Interoperability
    • eIDAS
  • Anonymity and Privacy
    • Privacy
    • IEEE Digital Privacy Model
    • Privacy with computing technology
    • Privacy and companies
    • Privacy and IAA
    • Identification
    • Authentication
    • Anonymity
    • Microdata privacy issues
    • Microdata privacy enhancing
    • L-Diversity
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  • Set-UID mechanism
  • Set-UID/Set-GID decision flowchart
  1. Linux Security Mechanisms

Privilege Elevation

Set-UID mechanism

Change the effective UID of a process running a program stored on a Set-UID file.

  • If a program file is owned by UID X and the set-UID bit of its ACL is set, then it will be executed in a process with UID X.

    • Independently of the UID of the subject that executed the program.

Allows normal users to execute privileged tasks encapsulated in administration programs.

  • Change the user’s password (passwd).

  • Change to super-user mode (su, sudo)

  • Mount devices (mount).

Effective UID / Real UID.

  • Real UID (rUID) is the UID of the process creator.

    • App launcher.

  • Effective UID (eUID) is the UID of the process.

    • The one that matters for defining the rights of the process.

    • eUID may differ from rUID.

UID change.

  • Ordinary application.

    • eUID = rUID = UID of the process that executed exec.

    • eUID cannot be changed (unless = 0).

  • Set-UID application.

    • eUID = UID of exec’d application file, rUID = initial process UID.

    • eUID can revert to rUID.

  • rUID cannot change

Set-UID/Set-GID decision flowchart

exec ( path, …).

  • File referred by path has Set-UID?

    • Yes

      • ID = path owner.

        • Change the process effective UID to ID of the path owner.

    • No.

      • Do nothing.

  • File referred by path has Set-GID?

    • Yes

      • ID = path GID.

      • Change the process GIDs to ID only.

    • No

      • Do nothing.

Last updated 1 year ago