lib: Add per-user packet pools

The IRMd will now check the user UID and GID for privileged access,
avoiding unprivileged users being able to disrupt all IPC (e.g. by
shm_open the single pool and corrupting its metadata).

Non-privileged users are now limited to a PUP (per-user pool) for
sending/receiving packets. It is still created by the IRMd, but owned
by the user (uid) with 600 permissions. It does not add additional
copies for local IPC between their own processes (i.e. over the local
IPCP), but packets between processes owned by a different user or
destined over the network (other IPCPs) will incur a copy when
crossing the PUP / PUP or the PUP / GSPP boundary.

Privileged users and users in the ouroboros group still have direct
access to the GSPP (globally shared private pool) for packet transfer
that will avoid additional copies when processing packets between
processes owned by different users and to the network.

This aligns the security model with UNIX trust domains defined by UID
and GID by leveraging file permission on the pools in shared memory.

┌─────────────────────────────────────────────────────────────┐
│ Source Pool    │ Dest Pool      │ Operation    │ Copies     │
├─────────────────────────────────────────────────────────────┤
│ GSPP           │ GSPP           │ Zero-copy    │ 0          │
│ PUP.uid        │ PUP.uid        │ Zero-copy    │ 0          │
│ PUP.uid1       │ PUP.uid2       │ memcpy()     │ 1          │
│ PUP.uid        │ GSPP           │ memcpy()     │ 1          │
│ GSPP           │ PUP.uid        │ memcpy()     │ 1          │
└─────────────────────────────────────────────────────────────┘

This also renames the struct ai ("application instance") in dev.c to
struct proc (process).

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 63 insertions, 1 deletions

diff --git a/src/lib/utils.c b/src/lib/utils.c
index 74f8ce4f..cfddec62 100644
--- a/src/lib/utils.c
+++ b/src/lib/utils.c
@@ -20,11 +20,15 @@
  * Foundation, Inc., http://www.fsf.org/about/contact/.
  */
 
-#define _POSIX_C_SOURCE 200809L
+#define _DEFAULT_SOURCE
+
+#include "config.h"
 
 #include <ouroboros/utils.h>
 
 #include <ctype.h>
+#include <grp.h>
+#include <pwd.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -138,5 +142,63 @@ char ** argvdup(char ** argv)
         }
 
         argv_dup[argc] = NULL;
+
         return argv_dup;
 }
+
+bool is_ouroboros_member_uid(uid_t uid)
+{
+        struct group *  grp;
+        struct passwd * pw;
+        gid_t           gid;
+        gid_t *         groups = NULL;
+        int             ngroups;
+        int             i;
+
+        /* Root is always privileged */
+        if (uid == 0)
+                return true;
+
+        grp = getgrnam("ouroboros");
+        if (grp == NULL)
+                return false;
+
+        gid = grp->gr_gid;
+
+        pw = getpwuid(uid);
+        if (pw == NULL)
+                return false;
+
+        if (pw->pw_gid == gid)
+                return true;
+
+        ngroups = 0;
+        getgrouplist(pw->pw_name, pw->pw_gid, NULL, &ngroups);
+        if (ngroups <= 0)
+                return false;
+
+        groups = malloc(ngroups * sizeof(*groups));
+        if (groups == NULL)
+                return false;
+
+        if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) < 0) {
+                free(groups);
+                return false;
+        }
+
+        for (i = 0; i < ngroups; i++) {
+                if (groups[i] == gid) {
+                        free(groups);
+                        return true;
+                }
+        }
+
+        free(groups);
+
+        return false;
+}
+
+bool is_ouroboros_member(void)
+{
+        return is_ouroboros_member_uid(getuid());
+}