| Message ID | f83b60bd7b011bd663d1ccdbad73608327af00e9.1504591358.git.rgb@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 4, 2017 at 11:46 PM, Richard Guy Briggs <rgb@redhat.com> wrote: > The existing condition tested for process effective capabilities set by > file attributes but intended to ignore the change if the result was > unsurprisingly an effective full set in the case root is special with a > setuid root executable file and we are root. > > Stated again: > - When you execute a setuid root application, it is no surprise and > expected that it got all capabilities, so we do not want capabilities > recorded. > if (pE_grew && !(pE_fullset && (eff_root || real_root) && root_priveleged) ) > > Now make sure we cover other cases: > - If something prevented a setuid root app getting all capabilities and > it wound up with one capability only, then it is a surprise and should > be logged. When it is a setuid root file, we only want capabilities > when the process does not get full capabilities.. > root_priveleged && setuid_root && !pE_fullset > > - Similarly if a non-setuid program does pick up capabilities due to > file system based capabilities, then we want to know what capabilities > were picked up. When it has file system based capabilities we want > the capabilities. > !is_setuid && (has_fcap && pP_gained) > > - If it is a non-setuid file and it gets ambient capabilities, we want > the capabilities. > !is_setuid && pA_gained > > - These last two are combined into one due to the common first parameter. > > Related: https://github.com/linux-audit/audit-kernel/issues/16 > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com> > Reviewed-by: Serge Hallyn <serge@hallyn.com> > Acked-by: James Morris <james.l.morris@oracle.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > security/commoncap.c | 29 ++++++++++++++++++++++------- > 1 files changed, 22 insertions(+), 7 deletions(-) > > diff --git a/security/commoncap.c b/security/commoncap.c > index 759f3fa..afebfd3 100644 > --- a/security/commoncap.c > +++ b/security/commoncap.c > @@ -528,7 +528,7 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) > { return !gid_eq(new->egid, old->gid); } > > /* > - * Audit candidate if current->cap_effective is set > + * 1) Audit candidate if current->cap_effective is set > * > * We do not bother to audit if 3 things are true: > * 1) cap_effective has all caps > @@ -538,16 +538,31 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) > * > * Number 1 above might fail if you don't have a full bset, but I think > * that is interesting information to audit. > + * > + * A number of other conditions require logging: > + * 2) something prevented setuid root getting all caps > + * 3) non-setuid root gets fcaps > + * 4) non-setuid root gets ambient > */ > -static inline bool nonroot_raised_pE(struct cred *cred, kuid_t root) > +static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, > + kuid_t root, bool has_fcap) > { > bool ret = false; > > - if (__cap_grew(effective, ambient, cred) && > - !(__cap_full(effective, cred) && > - (__is_eff(root, cred) || __is_real(root, cred)) && > - root_privileged())) > + if ((__cap_grew(effective, ambient, new) && > + !(__cap_full(effective, new) && > + (__is_eff(root, new) || __is_real(root, new)) && > + root_privileged())) || > + (root_privileged() && > + __is_suid(root, new) && > + !__cap_full(effective, new)) || > + (!__is_setuid(new, old) && > + ((has_fcap && > + __cap_gained(permitted, new, old)) || > + __cap_gained(ambient, new, old)))) > + > ret = true; > + > return ret; > } > > @@ -628,7 +643,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) > if (WARN_ON(!cap_ambient_invariant_ok(new))) > return -EPERM; > > - if (nonroot_raised_pE(new, root_uid)) { > + if (nonroot_raised_pE(new, old, root_uid, has_fcap)) { > ret = audit_log_bprm_fcaps(bprm, new, old); > if (ret < 0) > return ret; > -- > 1.7.1 >
On Tue, Sep 5, 2017 at 2:46 AM, Richard Guy Briggs <rgb@redhat.com> wrote: > The existing condition tested for process effective capabilities set by > file attributes but intended to ignore the change if the result was > unsurprisingly an effective full set in the case root is special with a > setuid root executable file and we are root. > > Stated again: > - When you execute a setuid root application, it is no surprise and > expected that it got all capabilities, so we do not want capabilities > recorded. > if (pE_grew && !(pE_fullset && (eff_root || real_root) && root_priveleged) ) > > Now make sure we cover other cases: > - If something prevented a setuid root app getting all capabilities and > it wound up with one capability only, then it is a surprise and should > be logged. When it is a setuid root file, we only want capabilities > when the process does not get full capabilities.. > root_priveleged && setuid_root && !pE_fullset > > - Similarly if a non-setuid program does pick up capabilities due to > file system based capabilities, then we want to know what capabilities > were picked up. When it has file system based capabilities we want > the capabilities. > !is_setuid && (has_fcap && pP_gained) > > - If it is a non-setuid file and it gets ambient capabilities, we want > the capabilities. > !is_setuid && pA_gained > > - These last two are combined into one due to the common first parameter. > > Related: https://github.com/linux-audit/audit-kernel/issues/16 > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com> > Reviewed-by: Serge Hallyn <serge@hallyn.com> > Acked-by: James Morris <james.l.morris@oracle.com> > --- > security/commoncap.c | 29 ++++++++++++++++++++++------- > 1 files changed, 22 insertions(+), 7 deletions(-) I really don't like how this patchset has gotten so large, I would have preferred to see a patch (or two, or three, ...) that made the minimal number of changes necessary to fix the audit problem and then a follow-on patchset to do the rework you felt was worthwhile. Reviewing this was a real pain and I have very little confidence in my conclusions, please try to not do this again. Acked-by: Paul Moore <paul@paul-moore.com> > diff --git a/security/commoncap.c b/security/commoncap.c > index 759f3fa..afebfd3 100644 > --- a/security/commoncap.c > +++ b/security/commoncap.c > @@ -528,7 +528,7 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) > { return !gid_eq(new->egid, old->gid); } > > /* > - * Audit candidate if current->cap_effective is set > + * 1) Audit candidate if current->cap_effective is set > * > * We do not bother to audit if 3 things are true: > * 1) cap_effective has all caps > @@ -538,16 +538,31 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) > * > * Number 1 above might fail if you don't have a full bset, but I think > * that is interesting information to audit. > + * > + * A number of other conditions require logging: > + * 2) something prevented setuid root getting all caps > + * 3) non-setuid root gets fcaps > + * 4) non-setuid root gets ambient > */ > -static inline bool nonroot_raised_pE(struct cred *cred, kuid_t root) > +static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, > + kuid_t root, bool has_fcap) > { > bool ret = false; > > - if (__cap_grew(effective, ambient, cred) && > - !(__cap_full(effective, cred) && > - (__is_eff(root, cred) || __is_real(root, cred)) && > - root_privileged())) > + if ((__cap_grew(effective, ambient, new) && > + !(__cap_full(effective, new) && > + (__is_eff(root, new) || __is_real(root, new)) && > + root_privileged())) || > + (root_privileged() && > + __is_suid(root, new) && > + !__cap_full(effective, new)) || > + (!__is_setuid(new, old) && > + ((has_fcap && > + __cap_gained(permitted, new, old)) || > + __cap_gained(ambient, new, old)))) > + > ret = true; > + > return ret; > } > > @@ -628,7 +643,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) > if (WARN_ON(!cap_ambient_invariant_ok(new))) > return -EPERM; > > - if (nonroot_raised_pE(new, root_uid)) { > + if (nonroot_raised_pE(new, old, root_uid, has_fcap)) { > ret = audit_log_bprm_fcaps(bprm, new, old); > if (ret < 0) > return ret; > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/security/commoncap.c b/security/commoncap.c index 759f3fa..afebfd3 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -528,7 +528,7 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) { return !gid_eq(new->egid, old->gid); } /* - * Audit candidate if current->cap_effective is set + * 1) Audit candidate if current->cap_effective is set * * We do not bother to audit if 3 things are true: * 1) cap_effective has all caps @@ -538,16 +538,31 @@ static inline bool __is_setgid(struct cred *new, const struct cred *old) * * Number 1 above might fail if you don't have a full bset, but I think * that is interesting information to audit. + * + * A number of other conditions require logging: + * 2) something prevented setuid root getting all caps + * 3) non-setuid root gets fcaps + * 4) non-setuid root gets ambient */ -static inline bool nonroot_raised_pE(struct cred *cred, kuid_t root) +static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, + kuid_t root, bool has_fcap) { bool ret = false; - if (__cap_grew(effective, ambient, cred) && - !(__cap_full(effective, cred) && - (__is_eff(root, cred) || __is_real(root, cred)) && - root_privileged())) + if ((__cap_grew(effective, ambient, new) && + !(__cap_full(effective, new) && + (__is_eff(root, new) || __is_real(root, new)) && + root_privileged())) || + (root_privileged() && + __is_suid(root, new) && + !__cap_full(effective, new)) || + (!__is_setuid(new, old) && + ((has_fcap && + __cap_gained(permitted, new, old)) || + __cap_gained(ambient, new, old)))) + ret = true; + return ret; } @@ -628,7 +643,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) if (WARN_ON(!cap_ambient_invariant_ok(new))) return -EPERM; - if (nonroot_raised_pE(new, root_uid)) { + if (nonroot_raised_pE(new, old, root_uid, has_fcap)) { ret = audit_log_bprm_fcaps(bprm, new, old); if (ret < 0) return ret;
The existing condition tested for process effective capabilities set by file attributes but intended to ignore the change if the result was unsurprisingly an effective full set in the case root is special with a setuid root executable file and we are root. Stated again: - When you execute a setuid root application, it is no surprise and expected that it got all capabilities, so we do not want capabilities recorded. if (pE_grew && !(pE_fullset && (eff_root || real_root) && root_priveleged) ) Now make sure we cover other cases: - If something prevented a setuid root app getting all capabilities and it wound up with one capability only, then it is a surprise and should be logged. When it is a setuid root file, we only want capabilities when the process does not get full capabilities.. root_priveleged && setuid_root && !pE_fullset - Similarly if a non-setuid program does pick up capabilities due to file system based capabilities, then we want to know what capabilities were picked up. When it has file system based capabilities we want the capabilities. !is_setuid && (has_fcap && pP_gained) - If it is a non-setuid file and it gets ambient capabilities, we want the capabilities. !is_setuid && pA_gained - These last two are combined into one due to the common first parameter. Related: https://github.com/linux-audit/audit-kernel/issues/16 Signed-off-by: Richard Guy Briggs <rgb@redhat.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Acked-by: James Morris <james.l.morris@oracle.com> --- security/commoncap.c | 29 ++++++++++++++++++++++------- 1 files changed, 22 insertions(+), 7 deletions(-)