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authorLennart Poettering <lennart@poettering.net>2012-05-24 04:00:56 +0200
committerLennart Poettering <lennart@poettering.net>2012-05-24 04:00:56 +0200
commitec8927ca5940e809f0b72f530582c76f1db4f065 (patch)
treeb230d2458088a82b879afc39a2752d5fc674974e /src/shared/capability.c
parente056b01d8acea7fc06d52ef91d227d744faf5259 (diff)
main: add configuration option to alter capability bounding set for PID 1
This also ensures that caps dropped from the bounding set are also dropped from the inheritable set, to be extra-secure. Usually that should change very little though as the inheritable set is empty for all our uses anyway.
Diffstat (limited to 'src/shared/capability.c')
-rw-r--r--src/shared/capability.c89
1 files changed, 88 insertions, 1 deletions
diff --git a/src/shared/capability.c b/src/shared/capability.c
index b2cd9ed75e..08b7a209da 100644
--- a/src/shared/capability.c
+++ b/src/shared/capability.c
@@ -40,7 +40,8 @@ int have_effective_cap(int value) {
cap_flag_value_t fv;
int r;
- if (!(cap = cap_get_proc()))
+ cap = cap_get_proc();
+ if (!cap)
return -errno;
if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
@@ -84,3 +85,89 @@ unsigned long cap_last_cap(void) {
return p;
}
+
+int capability_bounding_set_drop(uint64_t drop, bool right_now) {
+ unsigned long i;
+ cap_t after_cap = NULL, temp_cap = NULL;
+ cap_flag_value_t fv;
+ int r;
+
+ /* If we are run as PID 1 we will lack CAP_SETPCAP by default
+ * in the effective set (yes, the kernel drops that when
+ * executing init!), so get it back temporarily so that we can
+ * call PR_CAPBSET_DROP. */
+
+ after_cap = cap_get_proc();
+ if (!after_cap)
+ return -errno;
+
+ if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0) {
+ cap_free(after_cap);
+ return -errno;
+ }
+
+ if (fv != CAP_SET) {
+ static const cap_value_t v = CAP_SETPCAP;
+
+ temp_cap = cap_dup(after_cap);
+ if (!temp_cap) {
+ r = -errno;
+ goto finish;
+ }
+
+ if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
+ r = -errno;
+ goto finish;
+ }
+
+ if (cap_set_proc(temp_cap) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ }
+
+ for (i = 0; i <= cap_last_cap(); i++) {
+
+ if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
+ cap_value_t v;
+
+ /* Drop it from the bounding set */
+ if (prctl(PR_CAPBSET_DROP, i) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ v = i;
+
+ /* Also drop it from the inheritable set, so
+ * that anything we exec() loses the
+ * capability for good. */
+ if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
+ r = -errno;
+ goto finish;
+ }
+
+ /* If we shall apply this right now drop it
+ * also from our own capability sets. */
+ if (right_now) {
+ if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
+ cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ }
+ }
+ }
+
+ r = 0;
+
+finish:
+ if (temp_cap)
+ cap_free(temp_cap);
+
+ if (after_cap) {
+ cap_set_proc(after_cap);
+ cap_free(after_cap);
+ }
+
+ return r;
+}