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Enhancing Security in Operating Systems: Authentication, Access Control, and Biometrics

This comprehensive guide explores key security concepts in operating systems, focusing on critical components such as authentication mechanisms, password management, token usage, and biometrics. It discusses various access control policies, including discretionary, mandatory, and role-based access, highlighting their enforcement methods. The text emphasizes the importance of auditing and monitoring to detect security issues, alongside mechanisms to safeguard against unauthorized access. By integrating these security layers, we aim to bolster system integrity and protect sensitive data from cyber threats.

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Enhancing Security in Operating Systems: Authentication, Access Control, and Biometrics

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  1. Operating Systems 15 - security PIETER HARTEL

  2. Contents • Authentication • Passwords • Tokens • Biometrics • Access control • Policies • Mechanisms • Auditing • Logs • Intrusion detection

  3. Passwords • Why the salt? • Salt: two characters of hashed password; 4096 possibilities

  4. Reading the password file • Output? • gccGetpwent.c • ./a.out | more • Is there a memory leak? • ls –l /etc/shadow /etc/passwd intmain(intargc, char* argv[]) { structpasswd *p; while ((p = getpwent()) != NULL) { printf("%s:%s:%d:%d:%s:%s:%s\n", p->pw_name, p->pw_passwd, p->pw_uid, p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell); } endpwent(); return 0; }

  5. Tokens • Advantages • Generally stronger than passwords • Disadvantages • May require special hardware • Can be lost • Authentication protocol • Static • Dynamic password generator • Challenge response Cyber-crime Science

  6. Biometrics [Jai00] A. K. Jain, L. Hong, and S. Pankanti. Biometric identification. Commun. ACM, 43(2):90-98, Feb 2000. http://doi.acm.org/10.1145/328236.328110 IIS

  7. Access control policies • Policy types • Discretionary • Mandatory • Role based

  8. Discretionary access control mechanisms (for “files”) • Enforcement by the reference monitor • The matrix is usually sliced (why?) • Access control list per object • Capabilities per subject

  9. Role based access control • Group user by role • Encourage users to switch role • Principle of the least privilege

  10. #define llszsizeof(structlastlog) intmain(intargc, char *argv[]) { FILE *fp=fopen("/var/log/lastlog", "r"); inti; for(i=1;i<argc;i++) { structpasswd *p = getpwnam(argv[i]); if(p == NULL) { printf("unknown user: %s\n", argv[i]); } else { structlastlogll; fseek(fp, p->pw_uid*llsz, 0); fread(&ll, llsz, 1, fp); printf("%s %s %s %s", argv[i], ll.ll_line, ll.ll_host, ctime(&ll.ll_time)); } } fclose(fp); return 0; } Monitoring logins • last • gccLastlog.c • ./a.out lecturer student • Is there a problem? • man 5 lastlog • ls –l /var/log/lastlog

  11. Summary • Authentication and access control try to prevent problems • Auditing tries to detect problems • Technology is only part of the problem • Mechanism and policy

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