Re: [PATCH v33 27/29] Audit: Add record for multiple object security contexts

On Thu, Mar 10, 2022 at 7:01 PM Casey Schaufler <casey(a)schaufler-ca.com&gt; wrote: > Create a new audit record AUDIT_MAC_OBJ_CONTEXTS. > An example of the MAC_OBJ_CONTEXTS (1421) record is: > > type=MAC_OBJ_CONTEXTS[1421] > msg=audit(1601152467.009:1050): > obj_selinux=unconfined_u:object_r:user_home_t:s0 > > When an audit event includes a AUDIT_MAC_OBJ_CONTEXTS record > the "obj=" field in other records in the event will be "obj=?". > An AUDIT_MAC_OBJ_CONTEXTS record is supplied when the system has > multiple security modules that may make access decisions based > on an object security context. > > Signed-off-by: Casey Schaufler <casey(a)schaufler-ca.com&gt; > --- > include/linux/audit.h | 5 +++ > include/uapi/linux/audit.h | 1 + > kernel/audit.c | 47 +++++++++++++++++++++++ > kernel/auditsc.c | 79 ++++++++++++-------------------------- > 4 files changed, 77 insertions(+), 55 deletions(-) ... > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h > index af0aaccfaf57..d25d76b29e3c 100644 > --- a/include/uapi/linux/audit.h > +++ b/include/uapi/linux/audit.h > @@ -144,6 +144,7 @@ > #define AUDIT_MAC_CALIPSO_ADD 1418 /* NetLabel: add CALIPSO DOI entry */ > #define AUDIT_MAC_CALIPSO_DEL 1419 /* NetLabel: del CALIPSO DOI entry */ > #define AUDIT_MAC_TASK_CONTEXTS 1420 /* Multiple LSM task contexts */ > +#define AUDIT_MAC_OBJ_CONTEXTS 1421 /* Multiple LSM objext contexts */ > > #define AUDIT_FIRST_KERN_ANOM_MSG 1700 > #define AUDIT_LAST_KERN_ANOM_MSG 1799 > diff --git a/kernel/audit.c b/kernel/audit.c > index ad825af203cf..ac92e7fc5aa6 100644 > --- a/kernel/audit.c > +++ b/kernel/audit.c > @@ -2202,6 +2202,53 @@ static void audit_buffer_aux_end(struct audit_buffer *ab) > ab->skb = skb_peek(&ab->skb_list); > } > > +void audit_log_object_context(struct audit_buffer *ab, struct lsmblob *blob) > +{ > + int i; > + int error; > + struct lsmcontext context; > + > + if (!lsm_multiple_contexts()) { > + error = security_secid_to_secctx(blob, &context, LSMBLOB_FIRST); > + if (error) { > + if (error != -EINVAL) > + goto error_path; > + return; > + } > + audit_log_format(ab, " obj=%s", context.context); > + security_release_secctx(&context); > + } else { > + audit_log_format(ab, " obj=?"); > + error = audit_buffer_aux_new(ab, AUDIT_MAC_OBJ_CONTEXTS); > + if (error) > + goto error_path; > + > + for (i = 0; i < LSMBLOB_ENTRIES; i++) { > + if (blob->secid[i] == 0) > + continue; > + error = security_secid_to_secctx(blob, &context, i); > + if (error) { > + if (error != -EINVAL) > + audit_panic("error in audit_log_object_context"); > + audit_log_format(ab, "%sobj_%s=?", > + i ? " " : "", > + lsm_slot_to_name(i)); > + } else { > + audit_log_format(ab, "%sobj_%s=%s", > + i ? " " : "", > + lsm_slot_to_name(i), > + context.context); > + security_release_secctx(&context); > + } > + } > + > + audit_buffer_aux_end(ab); > + } > + return; > + > +error_path: > + audit_panic("error in audit_log_object_context"); > +} The comment from patch 26/29 regarding the audit_panic() placement also applies to audit_log_object_context(). > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index 7848e7351cf9..923e4e3a5697 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -1114,36 +1114,25 @@ static inline void audit_free_context(struct audit_context *context) > kfree(context); > } > > -static int audit_log_pid_context(struct audit_context *context, pid_t pid, > - kuid_t auid, kuid_t uid, > - unsigned int sessionid, > - struct lsmblob *blob, char *comm) > +static void audit_log_pid_context(struct audit_context *context, pid_t pid, > + kuid_t auid, kuid_t uid, > + unsigned int sessionid, > + struct lsmblob *blob, char *comm) > { > struct audit_buffer *ab; > - struct lsmcontext lsmctx; > - int rc = 0; > > ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID); > if (!ab) > - return rc; > + return; > > audit_log_format(ab, "opid=%d oauid=%d ouid=%d oses=%d", pid, > from_kuid(&init_user_ns, auid), > from_kuid(&init_user_ns, uid), sessionid); > - if (lsmblob_is_set(blob)) { > - if (security_secid_to_secctx(blob, &lsmctx, LSMBLOB_FIRST)) { > - audit_log_format(ab, " obj=(none)"); > - rc = 1; > - } else { > - audit_log_format(ab, " obj=%s", lsmctx.context); > - security_release_secctx(&lsmctx); > - } > - } > + if (lsmblob_is_set(blob)) > + audit_log_object_context(ab, blob); > audit_log_format(ab, " ocomm="); > audit_log_untrustedstring(ab, comm); > audit_log_end(ab); > - > - return rc; > } > > static void audit_log_execve_info(struct audit_context *context, > @@ -1373,18 +1362,10 @@ static void show_special(struct audit_context *context, int *call_panic) > from_kgid(&init_user_ns, context->ipc.gid), > context->ipc.mode); > if (osid) { > - struct lsmcontext lsmcxt; > struct lsmblob blob; > > lsmblob_init(&blob, osid); > - if (security_secid_to_secctx(&blob, &lsmcxt, > - LSMBLOB_FIRST)) { > - audit_log_format(ab, " osid=%u", osid); > - *call_panic = 1; > - } else { > - audit_log_format(ab, " obj=%s", lsmcxt.context); > - security_release_secctx(&lsmcxt); > - } > + audit_log_object_context(ab, &blob); While we lose the "osid=X" in case of failure, the secid/SID is a private kernel value meaning it was always of questionable value.

-- paul-moore.com