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selinux: format all invalid context as untrusted

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The userspace tools expect all fields of the same name to be logged
consistently with the same encoding.  Since the invalid_context fields
contain untrusted strings in selinux_inode_setxattr()
and selinux_setprocattr(), encode all instances of this field the same
way as though they were untrusted even though
compute_sid_handle_invalid_context() and security_sid_mls_copy() are
trusted.

Please see github issue
https://github.com/linux-audit/audit-kernel/issues/57

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Richard Guy Briggs 2019-06-27 12:48:01 -04:00 committed by Paul Moore
parent 464c258aa4
commit ea74a685ad
1 changed files with 19 additions and 10 deletions
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29
security/selinux/ss/services.c
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@ -1584,6 +1584,7 @@ static int compute_sid_handle_invalid_context(
struct policydb *policydb = &state->ss->policydb;
char *s = NULL, *t = NULL, *n = NULL;
u32 slen, tlen, nlen;
struct audit_buffer *ab;
if (context_struct_to_string(policydb, scontext, &s, &slen))
goto out;
@ -1591,12 +1592,14 @@ static int compute_sid_handle_invalid_context(
goto out;
if (context_struct_to_string(policydb, newcontext, &n, &nlen))
goto out;
audit_log(audit_context(), GFP_ATOMIC, AUDIT_SELINUX_ERR,
"op=security_compute_sid invalid_context=%s"
" scontext=%s"
" tcontext=%s"
" tclass=%s",
n, s, t, sym_name(policydb, SYM_CLASSES, tclass-1));
ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_SELINUX_ERR);
audit_log_format(ab,
"op=security_compute_sid invalid_context=");
/* no need to record the NUL with untrusted strings */
audit_log_n_untrustedstring(ab, n, nlen - 1);
audit_log_format(ab, " scontext=%s tcontext=%s tclass=%s",
s, t, sym_name(policydb, SYM_CLASSES, tclass-1));
audit_log_end(ab);
out:
kfree(s);
kfree(t);
@ -3003,10 +3006,16 @@ int security_sid_mls_copy(struct selinux_state *state,
if (rc) {
if (!context_struct_to_string(policydb, &newcon, &s,
&len)) {
audit_log(audit_context(),
GFP_ATOMIC, AUDIT_SELINUX_ERR,
"op=security_sid_mls_copy "
"invalid_context=%s", s);
struct audit_buffer *ab;
ab = audit_log_start(audit_context(),
GFP_ATOMIC,
AUDIT_SELINUX_ERR);
audit_log_format(ab,
"op=security_sid_mls_copy invalid_context=");
/* don't record NUL with untrusted strings */
audit_log_n_untrustedstring(ab, s, len - 1);
audit_log_end(ab);
kfree(s);
}
goto out_unlock;