Masquage de l'information | EPFL Graph Search

Le masquage de l'information est une règle de microarchitecture informatique (architecture détaillée) étendant le principe d'encapsulation des données aux fonctions. Cette règle consiste à cacher les détails d'implémentation pour offrir une interface simple à comprendre et à utiliser. Implémentation Beaucoup de langages de programmations orientés objets comme Java ou C++ offrent des limitateurs d’accès (niveaux de visibilité) permettant d’implémenter aisément le masquage des fonctions membres. Les limitateurs traditionnels sont :

publique: les fonctions membres de toutes les autres classes ou modules peuvent accéder aux fonctions membres possédant le niveau de visibilité publique. Ces fonctions membres constituent l'interface du module ou de la classe. Le terme méthode est habituellement utilisé pour décrire ce type de fonctions membres.
protégée: l'accès aux fonctions membres protégées est réservé aux fonctions membres des classes héritières. Le terme méthode d'ex

Abstract Data Types Are Under Full Control with Ada 9X

Ada 83 did not provide enough control on the creation, assignment, and destruction of objects of user-defined types. This lack of control restricted type composition and prevented the full exercise of information hiding on Abstract Data Types. Ada 9X brings new mechanisms supporting the full control of Abstract Data Types, powerful type composition, and more extensive information hiding. With better control of Abstract Data Types, Ada code will be easier to write, understand, and reuse. Thus, applications written in Ada 9X will be safer. Keywords: Abstract data types, Information hiding, Ada 9X, Object initialization, User-defined Assignment, Object finalization, Memory Reclamation, Reference counting, Type composition.

ACM Press1994

SoK: Shining Light on Shadow Stacks

Mathias Josef Payer, Xiangyu Zhang

Control-Flow Hijacking attacks are the dominant attack vector against C/C++ programs. Control-Flow Integrity (CFI) solutions mitigate these attacks on the forward edge, i.e., indirect calls through function pointers and virtual calls. Protecting the backward edge is left to stack canaries, which are easily bypassed through information leaks. Shadow Stacks are a fully precise mechanism for protecting backwards edges, and should be deployed with CFI mitigations. We present a comprehensive analysis of all possible shadow stack mechanisms along three axes: performance, compatibility, and security. For performance comparisons we use SPEC CPU2006, while security and compatibility are qualitatively analyzed. Based on our study, we renew calls for a shadow stack design that leverages a dedicated register, resulting in low performance overhead, and minimal memory overhead, but sacrifices compatibility. We present case studies of our implementation of such a design, Shadesmar, on Phoronix and Apache to demonstrate the feasibility of dedicating a general purpose register to a security monitor on modern architectures, and Shadesmar's deployability. Our comprehensive analysis, including detailed case studies for our novel design, allows compiler designers and practitioners to select the correct shadow stack design for different usage scenarios. Shadow stacks belong to the class of defense mechanisms that require metadata about the program's state to enforce their defense policies. Protecting this metadata for deployed mitigations requires in-process isolation of a segment of the virtual address space. Prior work on defenses in this class has relied on information hiding to protect metadata. We show that stronger guarantees are possible by repurposing two new Intel x86 extensions for memory protection (MPX), and page table control (MPK). Building on our isolation efforts with MPX and MPK, we present the design requirements for a dedicated hardware mechanism to support intra-process memory isolation, and discuss how such a mechanism can empower the next wave of highly precise software security mitigations that rely on partially isolated information in a process.

IEEE COMPUTER SOC2019

SoK: Shining Light on Shadow Stacks

Mathias Josef Payer, Xiangyu Zhang

IEEE COMPUTER SOC2019