Fix: Use unix socket peercred for pid, uid, gid credentials

[lttng-ust.git] / liblttng-ust-ctl / ustctl.c

diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index cfff4b174a2e9c49ddf6f1e64d3fb08b85965731..0272d9b9331c6750c276993b14552bbeb6e565f2 100644 (file)
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -20,6 +20,8 @@
 #include <string.h>
 #include <sys/mman.h>
 #include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
 
 #include <lttng/ust-config.h>
 #include <lttng/ust-ctl.h>
@@ -2022,6 +2024,104 @@ int ustctl_has_perf_counters(void)
 
 #endif
 
+#ifdef __linux__
+/*
+ * Override application pid/uid/gid with unix socket credentials. If
+ * the application announced a pid matching our view, it means it is
+ * within the same pid namespace, so expose the ppid provided by the
+ * application.
+ */
+static
+int get_cred(int sock,
+       const struct ustctl_reg_msg *reg_msg,
+       uint32_t *pid,
+       uint32_t *ppid,
+       uint32_t *uid,
+       uint32_t *gid)
+{
+       struct ucred ucred;
+       socklen_t ucred_len = sizeof(struct ucred);
+       int ret;
+
+       ret = getsockopt(sock, SOL_SOCKET, SO_PEERCRED, &ucred, &ucred_len);
+       if (ret) {
+               return -LTTNG_UST_ERR_PEERCRED;
+       }
+       DBG("Unix socket peercred [ pid: %u, uid: %u, gid: %u ], "
+               "application registered claiming [ pid: %u, ppid: %u, uid: %u, gid: %u ]",
+               ucred.pid, ucred.uid, ucred.gid,
+               reg_msg->pid, reg_msg->ppid, reg_msg->uid, reg_msg->gid);
+       if (!ucred.pid) {
+               ERR("Unix socket credential pid=0. Refusing application in distinct, non-nested pid namespace.");
+               return -LTTNG_UST_ERR_PEERCRED_PID;
+       }
+       *pid = ucred.pid;
+       *uid = ucred.uid;
+       *gid = ucred.gid;
+       if (ucred.pid == reg_msg->pid) {
+               *ppid = reg_msg->ppid;
+       } else {
+               *ppid = 0;
+       }
+       return 0;
+}
+#elif defined(__FreeBSD__)
+#include <sys/ucred.h>
+
+/*
+ * Override application uid/gid with unix socket credentials. Use the
+ * first group of the cr_groups.
+ * Use the pid and ppid provided by the application on registration.
+ */
+static
+int get_cred(int sock,
+       const struct ustctl_reg_msg *reg_msg,
+       uint32_t *pid,
+       uint32_t *ppid,
+       uint32_t *uid,
+       uint32_t *gid)
+{
+       struct xucred xucred;
+       socklen_t xucred_len = sizeof(struct xucred);
+       int ret;
+
+       ret = getsockopt(sock, SOL_SOCKET, LOCAL_PEERCRED, &xucred, &xucred_len);
+       if (ret) {
+               return -LTTNG_UST_ERR_PEERCRED;
+       }
+       if (xucred.cr_version != XUCRED_VERSION || xucred.cr_ngroups < 1) {
+               return -LTTNG_UST_ERR_PEERCRED;
+       }
+       DBG("Unix socket peercred [ uid: %u, gid: %u ], "
+               "application registered claiming [ pid: %d, ppid: %d, uid: %u, gid: %u ]",
+               xucred.uid, xucred.cr_groups[0],
+               reg_msg->pid, reg_msg->ppid, reg_msg->uid, reg_msg->gid);
+       *pid = reg_msg->pid;
+       *ppid = reg_msg->ppid;
+       *uid = xucred.uid;
+       *gid = xucred.cr_groups[0];
+       return 0;
+}
+#else
+#warning "Using insecure fallback: trusting user id provided by registered applications. Please consider implementing use of unix socket credentials on your platform."
+static
+int get_cred(int sock,
+       const struct ustctl_reg_msg *reg_msg,
+       uint32_t *pid,
+       uint32_t *ppid,
+       uint32_t *uid,
+       uint32_t *gid)
+{
+       DBG("Application registered claiming [ pid: %u, ppid: %d, uid: %u, gid: %u ]",
+               reg_msg->pid, reg_msg->ppid, reg_msg->uid, reg_msg->gid);
+       *pid = reg_msg->pid;
+       *ppid = reg_msg->ppid;
+       *uid = reg_msg->uid;
+       *gid = reg_msg->gid;
+       return 0;
+}
+#endif
+
 /*
  * Returns 0 on success, negative error value on error.
  */
@@ -2072,10 +2172,6 @@ int ustctl_recv_reg_msg(int sock,
        }
        *major = reg_msg.major;
        *minor = reg_msg.minor;
-       *pid = reg_msg.pid;
-       *ppid = reg_msg.ppid;
-       *uid = reg_msg.uid;
-       *gid = reg_msg.gid;
        *bits_per_long = reg_msg.bits_per_long;
        *uint8_t_alignment = reg_msg.uint8_t_alignment;
        *uint16_t_alignment = reg_msg.uint16_t_alignment;
@@ -2087,8 +2183,7 @@ int ustctl_recv_reg_msg(int sock,
                        reg_msg.major > LTTNG_UST_ABI_MAJOR_VERSION) {
                return -LTTNG_UST_ERR_UNSUP_MAJOR;
        }
-
-       return 0;
+       return get_cred(sock, &reg_msg, pid, ppid, uid, gid);
 }
 
 int ustctl_recv_notify(int sock, enum ustctl_notify_cmd *notify_cmd)