From 0e85048f53e46f30f26540fe3f6ae755d4d52ad1 Mon Sep 17 00:00:00 2001 From: Wolfgang Bumiller <Blub@users.noreply.github.com> Date: Thu, 8 Mar 2018 00:40:42 +0100 Subject: Take user namespaces into account in policy checks Change file related checks to use user namespaces and make sure involved uids/gids are mappable in the current namespace. Note that checks without file ownership information will still not take user namespaces into account, as some of these should be handled via 'zfs allow' (otherwise root in a user namespace could issue commands such as `zpool export`). This also adds an initial user namespace regression test for the setgid bit loss, with a user_ns_exec helper usable in further tests. Additionally, configure checks for the required user namespace related features are added for: * ns_capable * kuid/kgid_has_mapping() * user_ns in cred_t Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com> Closes #6800 Closes #7270 --- module/zfs/policy.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 59 insertions(+), 7 deletions(-) (limited to 'module') diff --git a/module/zfs/policy.c b/module/zfs/policy.c index 03e8f748b..55c932747 100644 --- a/module/zfs/policy.c +++ b/module/zfs/policy.c @@ -42,19 +42,47 @@ * all other cases this function must fail and return the passed err. */ static int -priv_policy(const cred_t *cr, int capability, boolean_t all, int err) +priv_policy_ns(const cred_t *cr, int capability, boolean_t all, int err, + struct user_namespace *ns) { ASSERT3S(all, ==, B_FALSE); if (cr != CRED() && (cr != kcred)) return (err); +#if defined(CONFIG_USER_NS) && defined(HAVE_NS_CAPABLE) + if (!(ns ? ns_capable(ns, capability) : capable(capability))) +#else if (!capable(capability)) +#endif return (err); return (0); } +static int +priv_policy(const cred_t *cr, int capability, boolean_t all, int err) +{ + return (priv_policy_ns(cr, capability, all, err, NULL)); +} + +static int +priv_policy_user(const cred_t *cr, int capability, boolean_t all, int err) +{ + /* + * All priv_policy_user checks are preceeded by kuid/kgid_has_mapping() + * checks. If we cannot do them, we shouldn't be using ns_capable() + * since we don't know whether the affected files are valid in our + * namespace. Note that kuid_has_mapping() came after cred->user_ns, so + * we shouldn't need to re-check for HAVE_CRED_USER_NS + */ +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + return (priv_policy_ns(cr, capability, all, err, cr->user_ns)); +#else + return (priv_policy_ns(cr, capability, all, err, NULL)); +#endif +} + /* * Checks for operations that are either client-only or are used by * both clients and servers. @@ -102,10 +130,15 @@ secpolicy_vnode_any_access(const cred_t *cr, struct inode *ip, uid_t owner) if (zpl_inode_owner_or_capable(ip)) return (0); - if (priv_policy(cr, CAP_DAC_OVERRIDE, B_FALSE, EPERM) == 0) +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + if (!kuid_has_mapping(cr->user_ns, SUID_TO_KUID(owner))) + return (EPERM); +#endif + + if (priv_policy_user(cr, CAP_DAC_OVERRIDE, B_FALSE, EPERM) == 0) return (0); - if (priv_policy(cr, CAP_DAC_READ_SEARCH, B_FALSE, EPERM) == 0) + if (priv_policy_user(cr, CAP_DAC_READ_SEARCH, B_FALSE, EPERM) == 0) return (0); return (EPERM); @@ -120,7 +153,12 @@ secpolicy_vnode_chown(const cred_t *cr, uid_t owner) if (crgetfsuid(cr) == owner) return (0); - return (priv_policy(cr, CAP_FOWNER, B_FALSE, EPERM)); +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + if (!kuid_has_mapping(cr->user_ns, SUID_TO_KUID(owner))) + return (EPERM); +#endif + + return (priv_policy_user(cr, CAP_FOWNER, B_FALSE, EPERM)); } /* @@ -152,7 +190,12 @@ secpolicy_vnode_setdac(const cred_t *cr, uid_t owner) if (crgetfsuid(cr) == owner) return (0); - return (priv_policy(cr, CAP_FOWNER, B_FALSE, EPERM)); +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + if (!kuid_has_mapping(cr->user_ns, SUID_TO_KUID(owner))) + return (EPERM); +#endif + + return (priv_policy_user(cr, CAP_FOWNER, B_FALSE, EPERM)); } /* @@ -175,8 +218,12 @@ secpolicy_vnode_setid_retain(const cred_t *cr, boolean_t issuidroot) int secpolicy_vnode_setids_setgids(const cred_t *cr, gid_t gid) { +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + if (!kgid_has_mapping(cr->user_ns, SGID_TO_KGID(gid))) + return (EPERM); +#endif if (crgetfsgid(cr) != gid && !groupmember(gid, cr)) - return (priv_policy(cr, CAP_FSETID, B_FALSE, EPERM)); + return (priv_policy_user(cr, CAP_FSETID, B_FALSE, EPERM)); return (0); } @@ -222,7 +269,12 @@ secpolicy_vnode_setid_modify(const cred_t *cr, uid_t owner) if (crgetfsuid(cr) == owner) return (0); - return (priv_policy(cr, CAP_FSETID, B_FALSE, EPERM)); +#if defined(CONFIG_USER_NS) && defined(HAVE_KUID_HAS_MAPPING) + if (!kuid_has_mapping(cr->user_ns, SUID_TO_KUID(owner))) + return (EPERM); +#endif + + return (priv_policy_user(cr, CAP_FSETID, B_FALSE, EPERM)); } /* -- cgit v1.2.3