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author | Serge E. Hallyn <serue@us.ibm.com> | 2009-04-02 18:47:14 -0500 |
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committer | James Morris <jmorris@namei.org> | 2009-04-03 11:49:31 +1100 |
commit | b5f22a59c0356655a501190959db9f7f5dd07e3f (patch) | |
tree | 3c20437a6a3b7b7e980078bfbcd0d53cdeda7528 /security | |
parent | 3d43321b7015387cfebbe26436d0e9d299162ea1 (diff) | |
download | kernel_samsung_smdk4412-b5f22a59c0356655a501190959db9f7f5dd07e3f.zip kernel_samsung_smdk4412-b5f22a59c0356655a501190959db9f7f5dd07e3f.tar.gz kernel_samsung_smdk4412-b5f22a59c0356655a501190959db9f7f5dd07e3f.tar.bz2 |
don't raise all privs on setuid-root file with fE set (v2)
Distributions face a backward compatibility problem with starting to use
file capabilities. For instance, removing setuid root from ping and
doing setcap cap_net_raw=pe means that booting with an older kernel
or one compiled without file capabilities means ping won't work for
non-root users.
In order to replace the setuid root bit on a capability-unaware
program, one has to set the effective, or legacy, file capability,
which makes the capability effective immediately. This patch
uses the legacy bit as a queue to not automatically add full
privilege to a setuid-root program.
So, with this patch, an ordinary setuid-root program will run with
privilege. But if /bin/ping has both setuid-root and cap_net_raw in
fP and fE, then ping (when run by non-root user) will not run
with only cap_net_raw.
Changelog:
Apr 2 2009: Print a message once when such a binary is loaded,
as per James Morris' suggestion.
Apr 2 2009: Fix the condition to only catch uid!=0 && euid==0.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security')
-rw-r--r-- | security/commoncap.c | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/security/commoncap.c b/security/commoncap.c index 7cd61a5..97ac1f1 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -28,6 +28,28 @@ #include <linux/prctl.h> #include <linux/securebits.h> +/* + * If a non-root user executes a setuid-root binary in + * !secure(SECURE_NOROOT) mode, then we raise capabilities. + * However if fE is also set, then the intent is for only + * the file capabilities to be applied, and the setuid-root + * bit is left on either to change the uid (plausible) or + * to get full privilege on a kernel without file capabilities + * support. So in that case we do not raise capabilities. + * + * Warn if that happens, once per boot. + */ +static void warn_setuid_and_fcaps_mixed(char *fname) +{ + static int warned; + if (!warned) { + printk(KERN_INFO "warning: `%s' has both setuid-root and" + " effective capabilities. Therefore not raising all" + " capabilities.\n", fname); + warned = 1; + } +} + int cap_netlink_send(struct sock *sk, struct sk_buff *skb) { NETLINK_CB(skb).eff_cap = current_cap(); @@ -464,6 +486,15 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) if (!issecure(SECURE_NOROOT)) { /* + * If the legacy file capability is set, then don't set privs + * for a setuid root binary run by a non-root user. Do set it + * for a root user just to cause least surprise to an admin. + */ + if (effective && new->uid != 0 && new->euid == 0) { + warn_setuid_and_fcaps_mixed(bprm->filename); + goto skip; + } + /* * To support inheritance of root-permissions and suid-root * executables under compatibility mode, we override the * capability sets for the file. @@ -478,6 +509,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) if (new->euid == 0) effective = true; } +skip: /* Don't let someone trace a set[ug]id/setpcap binary with the revised * credentials unless they have the appropriate permit |