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, 9 insertions, 2 deletions

diff --git a/src/ipcpd/unicast/fa.c b/src/ipcpd/unicast/fa.c
index 06e4b043..07f5b46c 100644
--- a/src/ipcpd/unicast/fa.c
+++ b/src/ipcpd/unicast/fa.c
@@ -48,6 +48,7 @@
 #include "ipcp.h"
 #include "dt.h"
 #include "ca.h"
+#include "np1.h"
 
 #include <inttypes.h>
 #include <stdlib.h>
@@ -687,6 +688,12 @@ void fa_fini(void)
         pthread_rwlock_destroy(&fa.flows_lock);
 }
 
+static int np1_flow_read_fa(int                   fd,
+                            struct ssm_pk_buff ** spb)
+{
+        return np1_flow_read(fd, spb, NP1_GET_POOL(fd));
+}
+
 int fa_start(void)
 {
 #ifndef BUILD_CONTAINER
@@ -695,7 +702,7 @@ int fa_start(void)
         int                 max;
 #endif
 
-        fa.psched = psched_create(packet_handler, np1_flow_read);
+        fa.psched = psched_create(packet_handler, np1_flow_read_fa);
         if (fa.psched == NULL) {
                 log_err("Failed to start packet scheduler.");
                 goto fail_psched;
@@ -963,7 +970,7 @@ void  fa_np1_rcv(uint64_t             eid,
 
         pthread_rwlock_unlock(&fa.flows_lock);
 
-        if (ipcp_flow_write(fd, spb) < 0) {
+        if (np1_flow_write(fd, spb, NP1_GET_POOL(fd)) < 0) {
                 log_dbg("Failed to write to flow %d.", fd);
                 ipcp_spb_release(spb);
 #ifdef IPCP_FLOW_STATS