core: add a concept of "dynamic" user ids, that are allocated as long as a service...

This adds a new boolean setting DynamicUser= to service files. If set, a new
user will be allocated dynamically when the unit is started, and released when
it is stopped. The user ID is allocated from the range 61184..65519. The user
will not be added to /etc/passwd (but an NSS module to be added later should
make it show up in getent passwd).

For now, care should be taken that the service writes no files to disk, since
this might result in files owned by UIDs that might get assigned dynamically to
a different service later on. Later patches will tighten sandboxing in order to
ensure that this cannot happen, except for a few selected directories.

A simple way to test this is:

        elogind-run -p DynamicUser=1 /bin/sleep 99999

diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index f47a8f04e0399c16233ebad5b9b8481681363e9c..16646ff9d83987bc90b0d4a303fe65a9b6bbaf10 100644 (file)
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -1052,3 +1052,17 @@ int flush_accept(int fd) {
         }
 }
 #endif // 0
+
+struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length) {
+        struct cmsghdr *cmsg;
+
+        assert(mh);
+
+        CMSG_FOREACH(cmsg, mh)
+                if (cmsg->cmsg_level == level &&
+                    cmsg->cmsg_type == type &&
+                    (length == (socklen_t) -1 || length == cmsg->cmsg_len))
+                        return cmsg;
+
+        return NULL;
+}

diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index b5d1dc3ed45b0bbf7296e6b9a3625b0a9067eb74..a88ab9fd225026dcca56c04483850d79dc6381a6 100644 (file)
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -150,6 +150,8 @@ int flush_accept(int fd);
 #define CMSG_FOREACH(cmsg, mh)                                          \
         for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))
 
+struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length);
+
 /* Covers only file system and abstract AF_UNIX socket addresses, but not unnamed socket addresses. */
 #define SOCKADDR_UN_LEN(sa)                                             \
         ({                                                              \

diff --git a/src/libelogind/sd-bus/bus-common-errors.c b/src/libelogind/sd-bus/bus-common-errors.c
index 6457cfe093a183cea5e3fe790182e424b18fc54e..e38e2e0dcc1d0e0ec0eb2efafe504a36864ab9db 100644 (file)
--- a/src/libelogind/sd-bus/bus-common-errors.c
+++ b/src/libelogind/sd-bus/bus-common-errors.c
@@ -45,6 +45,7 @@ BUS_ERROR_MAP_ELF_REGISTER const sd_bus_error_map bus_common_errors[] = {
         SD_BUS_ERROR_MAP(BUS_ERROR_NO_ISOLATION,                 EPERM),
         SD_BUS_ERROR_MAP(BUS_ERROR_SHUTTING_DOWN,                ECANCELED),
         SD_BUS_ERROR_MAP(BUS_ERROR_SCOPE_NOT_RUNNING,            EHOSTDOWN),
+        SD_BUS_ERROR_MAP(BUS_ERROR_NO_SUCH_DYNAMIC_USER,         ESRCH),
 
         SD_BUS_ERROR_MAP(BUS_ERROR_NO_SUCH_MACHINE,              ENXIO),
         SD_BUS_ERROR_MAP(BUS_ERROR_NO_SUCH_IMAGE,                ENOENT),