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bus: use EUID over UID and fix unix-creds

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Whenever a process performs an action on an object, the kernel uses the
EUID of the process to do permission checks and to apply on any newly
created objects. The UID of a process is only used if someone *ELSE* acts
on the process. That is, the UID of a process defines who owns the
process, the EUID defines what privileges are used by this process when
performing an action.

Process limits, on the other hand, are always applied to the real UID, not
the effective UID. This is, because a process has a user object linked,
which always corresponds to its UID. A process never has a user object
linked for its EUID. Thus, accounting (and limits) is always done on the
real UID.

This commit fixes all sd-bus users to use the EUID when performing
privilege checks and alike. Furthermore, it fixes unix-creds to be parsed
as EUID, not UID (as the kernel always takes the EUID on UDS). Anyone
using UID (eg., to do user-accounting) has to fall back to the EUID as UDS
does not transmit the UID.
This commit is contained in:
David Herrmann
2015-01-18 13:55:55 +01:00
parent e23f4bb525
commit 05bae4a60c
9 changed files with 42 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libsystemd/sd-bus/bus-control.c
+8 -8
View File
@@ -762,7 +762,7 @@ static int bus_get_name_creds_dbus1(
if ((mask & SD_BUS_CREDS_PID) ||
((mask & SD_BUS_CREDS_AUGMENT) &&
(mask & (SD_BUS_CREDS_EUID|SD_BUS_CREDS_SUID|SD_BUS_CREDS_FSUID|
(mask & (SD_BUS_CREDS_UID|SD_BUS_CREDS_SUID|SD_BUS_CREDS_FSUID|
SD_BUS_CREDS_GID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_SGID|SD_BUS_CREDS_FSGID|
SD_BUS_CREDS_COMM|SD_BUS_CREDS_EXE|SD_BUS_CREDS_CMDLINE|
SD_BUS_CREDS_CGROUP|SD_BUS_CREDS_UNIT|SD_BUS_CREDS_USER_UNIT|SD_BUS_CREDS_SLICE|SD_BUS_CREDS_SESSION|SD_BUS_CREDS_OWNER_UID|
@@ -798,7 +798,7 @@ static int bus_get_name_creds_dbus1(
reply = sd_bus_message_unref(reply);
}
if (mask & SD_BUS_CREDS_UID) {
if (mask & SD_BUS_CREDS_EUID) {
uint32_t u;
r = sd_bus_call_method(
@@ -818,8 +818,8 @@ static int bus_get_name_creds_dbus1(
if (r < 0)
return r;
c->uid = u;
c->mask |= SD_BUS_CREDS_UID;
c->euid = u;
c->mask |= SD_BUS_CREDS_EUID;
reply = sd_bus_message_unref(reply);
}
@@ -961,13 +961,13 @@ static int bus_get_owner_creds_dbus1(sd_bus *bus, uint64_t mask, sd_bus_creds **
}
if (bus->ucred.uid != UID_INVALID) {
c->uid = bus->ucred.uid;
c->mask |= SD_BUS_CREDS_UID & mask;
c->euid = bus->ucred.uid;
c->mask |= SD_BUS_CREDS_EUID & mask;
}
if (bus->ucred.gid != GID_INVALID) {
c->gid = bus->ucred.gid;
c->mask |= SD_BUS_CREDS_GID & mask;
c->egid = bus->ucred.gid;
c->mask |= SD_BUS_CREDS_EGID & mask;
}
}
src/libsystemd/sd-bus/bus-message.c
+6 -6
View File
@@ -424,19 +424,19 @@ int bus_message_from_header(
if (ucred) {
m->creds.pid = ucred->pid;
m->creds.uid = ucred->uid;
m->creds.gid = ucred->gid;
m->creds.euid = ucred->uid;
m->creds.egid = ucred->gid;
/* Due to namespace translations some data might be
* missing from this ucred record. */
if (m->creds.pid > 0)
m->creds.mask |= SD_BUS_CREDS_PID;
if (m->creds.uid != UID_INVALID)
m->creds.mask |= SD_BUS_CREDS_UID;
if (m->creds.euid != UID_INVALID)
m->creds.mask |= SD_BUS_CREDS_EUID;
if (m->creds.gid != GID_INVALID)
m->creds.mask |= SD_BUS_CREDS_GID;
if (m->creds.egid != GID_INVALID)
m->creds.mask |= SD_BUS_CREDS_EGID;
}
if (label) {
src/libsystemd/sd-bus/busctl.c
+2 -2
View File
@@ -160,7 +160,7 @@ static int list_bus_names(sd_bus *bus, char **argv) {
r = sd_bus_get_name_creds(
bus, *i,
(arg_augment_creds ? SD_BUS_CREDS_AUGMENT : 0) |
SD_BUS_CREDS_UID|SD_BUS_CREDS_PID|SD_BUS_CREDS_COMM|
SD_BUS_CREDS_EUID|SD_BUS_CREDS_PID|SD_BUS_CREDS_COMM|
SD_BUS_CREDS_UNIQUE_NAME|SD_BUS_CREDS_UNIT|SD_BUS_CREDS_SESSION|
SD_BUS_CREDS_DESCRIPTION, &creds);
if (r >= 0) {
@@ -178,7 +178,7 @@ static int list_bus_names(sd_bus *bus, char **argv) {
} else
fputs(" - - ", stdout);
r = sd_bus_creds_get_uid(creds, &uid);
r = sd_bus_creds_get_euid(creds, &uid);
if (r >= 0) {
_cleanup_free_ char *u = NULL;