Projects/Audit
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This is an early stage project for MIT Kerberos. It is being fleshed out by its proponents. Feel free to help flesh out the details of this project. After the project is ready, it will be presented for review and approval.
Contents
Purpose
The focus of this project will be on creating an Audit infrastructure within MIT Kerberos to monitor security related events on the KDC. The initial set of the audible events will be identified.
Requirements
The new audit system should be:
- build-time enabled;
- run-time pluggable;
- simple, so it could be easily replaced with the OS specific implementations;
- if possible, prepare i18n- and l10n-ready log messages.
Events
This section details the list of the categories of the auditable events and the associated information.
- Audit module loaded/unloaded
- Startup and shutdown of the audit system must be recorded by audit system;
- KDC started/stopped
- KDC startup - KDC clockskew, clock_adjusted, list of realms, ports, location and names of the plugins, the values of allow_weak_crypto, kdc_req_sumtype, default_ap_req_sumtype and default_safe_sumtype;
- AS exchange
- AS attempt (unsuccessful) - parsed client and server names, port number, key types and flags, ticket start and end times, rep_srv_data, pre-auth type used, KDC status message,
- AS done (success): parsed client and server names, port number, ktypes and flags, ticket start, end and renew until times, authentication time and kdc time timestamps, session enckey type, rep_srv_data, pre-auth type used, KDC status message,
- TGS exchange
- Successful or unsuccessful attempt;
- Alternative TGS;
- Session keys
- AS and TGS exchange session key generation;
- AS and TGS exchange session key cleaning;
- Policy
- Policies violation when processing requests - TBD;
Design details
Pluggable interface
/* Audit plugin vtable */
typedef struct krb5_audit_vtable_st {
/* Mandatory: name of module. */
char *name;
kau_open_fn open;
kau_close_fn close;
kau_kdc_start_fn kdc_start;
kau_kdc_stop_fn kdc_stop;
kau_as_req_attempt_fn as_req_attempt;
kau_as_req_done_fn as_req_done;
kau_tgs_fn tgs;
kau_tgs_alt_fn tgs_alt;
kau_sesskey_as_generated_fn sesskey_as_generated;
kau_sesskey_as_cleared_fn sesskey_as_cleared;
kau_sesskey_tgs_generated_fn sesskey_tgs_generated;
kau_sesskey_tgs_cleared_fn sesskey_tgs_cleared;
} *krb5_audit_vtable;
typedef krb5_error_code (*kau_open_fn)(krb5_context context , kau_ctx *au_ctx);
typedef krb5_error_code (*kau_close_fn)(krb5_context context, kau_ctx au_ctx);
typedef krb5_error_code (*kau_kdc_stop_fn)(krb5_context context, kau_ctx au_ctx, krb5_error_code status);
typedef krb5_error_code
(*kau_kdc_start_fn)(krb5_context context, kau_ctx au_ctx,
krb5_deltat clockskew, krb5_flags clock_adjusted,
const char *realm_port, krb5_boolean allow_weak_crypto,
const char *plugins, const char *plugin_dir,
krb5_cksumtype kdc_req_sumtype,
krb5_cksumtype default_ap_req_sumtype,
krb5_cksumtype default_safe_sumtype,
int status);
typedef krb5_error_code
(*kau_as_req_attempt_fn)(krb5_context context, kau_ctx au_ctx,
const char *cname, const char *sname, const char *status_msg,
const int from_port, const char * ktypes,
krb5_flags flags,
krb5_deltat start_time, krb5_deltat endtime,
char *rep_srv_data, int patype,
krb5_error_code status);
typedef krb5_error_code
(*kau_as_req_done_fn)(krb5_context context, kau_ctx au_ctx,
krb5_timestamp authtime, krb5_timestamp kdc_time,
const char *cname, const char *sname, const char *status_msg,
const int from_port, krb5_flags flags,
const char *ktypes, krb5_enctype sk1_etype,
krb5_deltat tkt_start_time, krb5_deltat tkt_end_time,
krb5_deltat tkt_renew_till,
char *rep_srv_data, int patype,
krb5_error_code status);
typedef krb5_error_code
(*kau_tgs_fn)(krb5_context context, kau_ctx au_ctx,
krb5_timestamp authtime, krb5_timestamp kdc_time,
const char *cname, const char *sname,
const char *altcname, const char *s4u_name,
krb5_flags flags, const char *status_msg,
const int from_port, const char * ktypes_buf, krb5_enctype useenctype,
const int is_referral, krb5_error_code status);
typedef krb5_error_code
(*kau_tgs_alt_fn)(krb5_context context, kau_ctx au_ctx,
const char *sname, krb5_error_code status);
typedef krb5_error_code
(*kau_sesskey_as_generated_fn)(krb5_context context, kau_ctx au_ctx,
const char *cname, const char *sname,
const char *status_msg,
const int from_port, const char * ktypes,
krb5_enctype used_ktype,
krb5_error_code status);
typedef krb5_error_code
(*kau_sesskey_as_cleared_fn)(krb5_context context, kau_ctx au_ctx,
const char *cname, const char *sname,
const char *status_msg,
const int from_port, krb5_enctype used_ktype,
krb5_error_code status);
typedef krb5_error_code
(*kau_sesskey_tgs_generated_fn)(krb5_context context, kau_ctx au_ctx,
const char *cname, const char *sname,
const char *status_msg, const int from_port,
const char *ktypes, krb5_enctype used_ktype,
krb5_error_code status);
typedef krb5_error_code
(*kau_sesskey_tgs_cleared_fn)(krb5_context context, kau_ctx au_ctx,
const char *cname, const char *sname,
const char *status_msg,
const int from_port, krb5_enctype used_ktype,
krb5_error_code status);
API signatures
/* Audit plugin loaded/unloaded */ krb5_error_code load_audit_plugin(krb5_context context); krb5_error_code unload_audit_plugin(krb5_context context);
/* KDC started /stopped */ krb5_error_code kau_kdc_start(krb5_context context, int status); krb5_error_code kau_kdc_stop(krb5_context context, krb5_error_code status);
/* AS exchange: AS attempt (unsuccessful) and AS done (success) */ krb5_error_code kau_as_req_done(krb5_context context, struct as_req_state *state, krb5_error_code status); krb5_error_code kau_as_req_attempt(krb5_context context, struct as_req_state *state, krb5_error_code status);
/* TGS exchange: Successful or unsuccessful attempt and alternative TGS */ krb5_error_code kau_tgs(krb5_context context, struct tgs_req_audit_state *state, krb5_error_code status); krb5_error_code kau_tgs_alt(krb5_context context, struct tgs_req_audit_state *state, krb5_error_code status);
/* Session key generation and cleaning them up */ krb5_error_code kau_sesskey_as_generated(krb5_context context, struct as_req_state *state, krb5_error_code status); krb5_error_code kau_sesskey_as_cleared(krb5_context context, struct as_req_state *state, krb5_error_code status); krb5_error_code kau_sesskey_tgs_generated(krb5_context context, struct tgs_req_audit_state *state, krb5_error_code status); krb5_error_code kau_sesskey_tgs_cleared(krb5_context context,struct tgs_req_audit_state *state, krb5_error_code status);
/* Policy driven events - TBD */ krb5_error_code kau_policy(krb5_context context, ... , krb5_error_code status);
/* Name of audit module */ krb5_error_code kau_plugin_name(krb5_context context, char **name);
Configuration
The following ./configure options are added:
- --enable-audit[=yes/no]
- Enable audit plugin. By default at build time audit is disabled.
- --with-audit-plugin=simple
- (For demo and testing purposes) Build the audit plugin "simple".
Test implementation
We will use libaudit module available on Fedora, Debian, Suse for the first round.
Some "simple" audit plugin will be implemented and Python test system will become aware of its existence. New ./configure --with-audit-plugin option will be introduced to build "simple" audit plugin for testing purpose. If audit is enabled and audit plugin is available, "make check" will store audit messages into audit log file.
References
- . Common Criteria for Information Technology Security Evaluation http://www.commoncriteriaportal.org/files/ccfiles/CCPART2V3.1R4.pdf
- . Oracle Solaris Auditing http://docs.oracle.com/cd/E19963-01/html/821-1456/auditov-1.html
- . Understanding Linux Audit http://doc.opensuse.org/products/draft/SLES/SLES-security_sd_draft/cha.audit.comp.html
- . Events Classification in Log Audit http://airccse.org/journal/nsa/0410ijnsa5.pdf
