chiark / gitweb /
bus-proxy: beef up policy enforcement
[elogind.git] / src / bus-proxyd / bus-policy.c
index e870fbc9485aa735aa244947bdff55f2efe28dd9..3cfe9befb2ffc70876264bcafec8403591b762d2 100644 (file)
@@ -24,6 +24,7 @@
 #include "strv.h"
 #include "conf-files.h"
 #include "bus-internal.h"
+#include "bus-message.h"
 #include "bus-policy.h"
 
 static void policy_item_free(PolicyItem *i) {
@@ -591,6 +592,294 @@ static int file_load(Policy *p, const char *path) {
         }
 }
 
+enum {
+        DENY,
+        ALLOW,
+        DUNNO,
+};
+
+static const char *verdict_to_string(int v) {
+        switch (v) {
+
+        case DENY:
+                return "DENY";
+        case ALLOW:
+                return "ALLOW";
+        case DUNNO:
+                return "DUNNO";
+        }
+
+        return NULL;
+}
+
+struct policy_check_filter {
+        PolicyItemClass class;
+        uid_t uid;
+        gid_t gid;
+        int message_type;
+        const char *name;
+        const char *interface;
+        const char *path;
+        const char *member;
+};
+
+static int is_permissive(PolicyItem *i) {
+
+        assert(i);
+
+        return (i->type == POLICY_ITEM_ALLOW) ? ALLOW : DENY;
+}
+
+static int check_policy_item(PolicyItem *i, const struct policy_check_filter *filter) {
+
+        assert(i);
+        assert(filter);
+
+        switch (i->class) {
+        case POLICY_ITEM_SEND:
+        case POLICY_ITEM_RECV:
+
+                if (i->name && !streq_ptr(i->name, filter->name))
+                        break;
+
+                if ((i->message_type != 0) && (i->message_type != filter->message_type))
+                        break;
+
+                if (i->path && !streq_ptr(i->path, filter->path))
+                        break;
+
+                if (i->member && !streq_ptr(i->member, filter->member))
+                        break;
+
+                if (i->interface && !streq_ptr(i->interface, filter->interface))
+                        break;
+
+                return is_permissive(i);
+
+        case POLICY_ITEM_OWN:
+                assert(filter->name);
+
+                if (streq(i->name, "*") || streq(i->name, filter->name))
+                        return is_permissive(i);
+                break;
+
+        case POLICY_ITEM_OWN_PREFIX:
+                assert(filter->name);
+
+                if (streq(i->name, "*") || service_name_startswith(filter->name, i->name))
+                        return is_permissive(i);
+                break;
+
+        case POLICY_ITEM_USER:
+                if (filter->uid != (uid_t) -1)
+                        if ((streq_ptr(i->name, "*") || (i->uid_valid && i->uid == filter->uid)))
+                                return is_permissive(i);
+                break;
+
+        case POLICY_ITEM_GROUP:
+                if (filter->gid != (gid_t) -1)
+                        if ((streq_ptr(i->name, "*") || (i->gid_valid && i->gid == filter->gid)))
+                                return is_permissive(i);
+                break;
+
+        case POLICY_ITEM_IGNORE:
+        default:
+                break;
+        }
+
+        return DUNNO;
+}
+
+static int check_policy_items(PolicyItem *items, const struct policy_check_filter *filter) {
+
+        PolicyItem *i;
+        int verdict = DUNNO;
+
+        assert(filter);
+
+        /* Check all policies in a set - a broader one might be followed by a more specific one,
+         * and the order of rules in policy definitions matters */
+        LIST_FOREACH(items, i, items) {
+                int v;
+
+                if (i->class != filter->class &&
+                    !(i->class == POLICY_ITEM_OWN_PREFIX && filter->class == POLICY_ITEM_OWN))
+                        continue;
+
+                v = check_policy_item(i, filter);
+                if (v != DUNNO)
+                        verdict = v;
+        }
+
+        return verdict;
+}
+
+static int policy_check(Policy *p, const struct policy_check_filter *filter) {
+
+        PolicyItem *items;
+        int verdict, v;
+
+        assert(p);
+        assert(filter);
+
+        assert(IN_SET(filter->class, POLICY_ITEM_SEND, POLICY_ITEM_RECV, POLICY_ITEM_OWN, POLICY_ITEM_USER, POLICY_ITEM_GROUP));
+
+        /*
+         * The policy check is implemented by the following logic:
+         *
+         *  1. Check default items
+         *  2. Check group items
+         *  3. Check user items
+         *  4. Check mandatory items
+         *
+         *  Later rules override earlier rules.
+         */
+
+        verdict = check_policy_items(p->default_items, filter);
+
+        if (filter->gid != (gid_t) -1) {
+                items = hashmap_get(p->group_items, UINT32_TO_PTR(filter->gid));
+                if (items) {
+                        v = check_policy_items(items, filter);
+                        if (v != DUNNO)
+                                verdict = v;
+                }
+        }
+
+        if (filter->uid != (uid_t) -1) {
+                items = hashmap_get(p->user_items, UINT32_TO_PTR(filter->uid));
+                if (items) {
+                        v = check_policy_items(items, filter);
+                        if (v != DUNNO)
+                                verdict = v;
+                }
+        }
+
+        v = check_policy_items(p->mandatory_items, filter);
+        if (v != DUNNO)
+                verdict = v;
+
+        return verdict;
+}
+
+bool policy_check_own(Policy *p, uid_t uid, gid_t gid, const char *name) {
+
+        struct policy_check_filter filter = {
+                .class = POLICY_ITEM_OWN,
+                .uid   = uid,
+                .gid   = gid,
+                .name  = name,
+        };
+
+        int verdict;
+
+        assert(p);
+        assert(name);
+
+        verdict = policy_check(p, &filter);
+
+        log_full(LOG_AUTH | (verdict != ALLOW ? LOG_WARNING : LOG_DEBUG),
+                 "Ownership permission check for uid=" UID_FMT " gid=" GID_FMT" name=%s: %s",
+                 uid, gid, strna(name), strna(verdict_to_string(verdict)));
+
+        return verdict == ALLOW;
+}
+
+bool policy_check_hello(Policy *p, uid_t uid, gid_t gid) {
+
+        struct policy_check_filter filter = {
+                .uid = uid,
+                .gid = gid,
+        };
+        int verdict;
+
+        assert(p);
+
+        filter.class = POLICY_ITEM_USER;
+        verdict = policy_check(p, &filter);
+
+        if (verdict != DENY) {
+                int v;
+
+                filter.class = POLICY_ITEM_GROUP;
+                v = policy_check(p, &filter);
+                if (v != DUNNO)
+                        verdict = v;
+        }
+
+        log_full(LOG_AUTH | (verdict != ALLOW ? LOG_WARNING : LOG_DEBUG),
+                 "Hello permission check for uid=" UID_FMT " gid=" GID_FMT": %s",
+                 uid, gid, strna(verdict_to_string(verdict)));
+
+        return verdict == ALLOW;
+}
+
+bool policy_check_recv(Policy *p,
+                       uid_t uid,
+                       gid_t gid,
+                       int message_type,
+                       const char *name,
+                       const char *path,
+                       const char *interface,
+                       const char *member) {
+
+        struct policy_check_filter filter = {
+                .class        = POLICY_ITEM_RECV,
+                .uid          = uid,
+                .gid          = gid,
+                .message_type = message_type,
+                .name         = name,
+                .interface    = interface,
+                .path         = path,
+                .member       = member,
+        };
+
+        int verdict;
+
+        assert(p);
+
+        verdict = policy_check(p, &filter);
+
+        log_full(LOG_AUTH | (verdict != ALLOW ? LOG_WARNING : LOG_DEBUG),
+                 "Recieve permission check for uid=" UID_FMT " gid=" GID_FMT" message=%s name=%s interface=%s path=%s member=%s: %s",
+                 uid, gid, bus_message_type_to_string(message_type), strna(name), strna(path), strna(interface), strna(member), strna(verdict_to_string(verdict)));
+
+        return verdict == ALLOW;
+}
+
+bool policy_check_send(Policy *p,
+                       uid_t uid,
+                       gid_t gid,
+                       int message_type,
+                       const char *name,
+                       const char *path,
+                       const char *interface,
+                       const char *member) {
+
+        struct policy_check_filter filter = {
+                .class        = POLICY_ITEM_SEND,
+                .uid          = uid,
+                .gid          = gid,
+                .message_type = message_type,
+                .name         = name,
+                .interface    = interface,
+                .path         = path,
+                .member       = member,
+        };
+
+        int verdict;
+
+        assert(p);
+
+        verdict = policy_check(p, &filter);
+
+        log_full(LOG_AUTH | (verdict != ALLOW ? LOG_WARNING : LOG_DEBUG),
+                 "Send permission check for uid=" UID_FMT " gid=" GID_FMT" message=%s name=%s interface=%s path=%s member=%s: %s",
+                 uid, gid, bus_message_type_to_string(message_type), strna(name), strna(path), strna(interface), strna(member), strna(verdict_to_string(verdict)));
+
+        return verdict == ALLOW;
+}
+
 int policy_load(Policy *p, char **files) {
         char **i;
         int r;
@@ -716,6 +1005,7 @@ static void dump_items(PolicyItem *items, const char *prefix) {
                         printf("%sGroup: %s (%d)\n",
                                prefix, strna(group), i->gid);
                 }
+                printf("%s-\n", prefix);
         }
 }