From 29206d4619843252c2e04f20dc03c246547600a2 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 14 Jul 2016 12:37:28 +0200 Subject: core: add a concept of "dynamic" user ids, that are allocated as long as a service is running 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: systemd-run -p DynamicUser=1 /bin/sleep 99999 --- Makefile.am | 2 ++ 1 file changed, 2 insertions(+) (limited to 'Makefile.am') diff --git a/Makefile.am b/Makefile.am index c9fb4917ad..3d5ce1e2c3 100644 --- a/Makefile.am +++ b/Makefile.am @@ -1197,6 +1197,8 @@ libcore_la_SOURCES = \ src/core/load-dropin.h \ src/core/execute.c \ src/core/execute.h \ + src/core/dynamic-user.c \ + src/core/dynamic-user.h \ src/core/kill.c \ src/core/kill.h \ src/core/dbus.c \ -- cgit v1.2.3-54-g00ecf From 409093fe10685ed55915ef256f09cdf144b6528b Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 14 Jul 2016 19:19:49 +0200 Subject: nss: add new "nss-systemd" NSS module for mapping dynamic users With this NSS module all dynamic service users will be resolvable via NSS like any real user. --- Makefile-man.am | 7 + Makefile.am | 21 +++ README | 21 ++- man/nss-myhostname.xml | 5 +- man/nss-mymachines.xml | 5 +- man/nss-resolve.xml | 7 +- man/nss-systemd.xml | 107 +++++++++++++ src/core/execute.c | 6 + src/nss-systemd/Makefile | 1 + src/nss-systemd/nss-systemd.c | 332 ++++++++++++++++++++++++++++++++++++++++ src/nss-systemd/nss-systemd.sym | 17 ++ 11 files changed, 515 insertions(+), 14 deletions(-) create mode 100644 man/nss-systemd.xml create mode 120000 src/nss-systemd/Makefile create mode 100644 src/nss-systemd/nss-systemd.c create mode 100644 src/nss-systemd/nss-systemd.sym (limited to 'Makefile.am') diff --git a/Makefile-man.am b/Makefile-man.am index 8ab733360d..3ac1906a4a 100644 --- a/Makefile-man.am +++ b/Makefile-man.am @@ -23,6 +23,7 @@ MANPAGES += \ man/localtime.5 \ man/machine-id.5 \ man/machine-info.5 \ + man/nss-systemd.8 \ man/os-release.5 \ man/sd-bus-errors.3 \ man/sd-bus.3 \ @@ -255,6 +256,7 @@ MANPAGES_ALIAS += \ man/SD_WARNING.3 \ man/init.1 \ man/journald.conf.d.5 \ + man/libnss_systemd.so.2.8 \ man/poweroff.8 \ man/reboot.8 \ man/sd_bus_creds_get_audit_login_uid.3 \ @@ -587,6 +589,7 @@ man/SD_NOTICE.3: man/sd-daemon.3 man/SD_WARNING.3: man/sd-daemon.3 man/init.1: man/systemd.1 man/journald.conf.d.5: man/journald.conf.5 +man/libnss_systemd.so.2.8: man/nss-systemd.8 man/poweroff.8: man/halt.8 man/reboot.8: man/halt.8 man/sd_bus_creds_get_audit_login_uid.3: man/sd_bus_creds_get_pid.3 @@ -1071,6 +1074,9 @@ man/init.html: man/systemd.html man/journald.conf.d.html: man/journald.conf.html $(html-alias) +man/libnss_systemd.so.2.html: man/nss-systemd.html + $(html-alias) + man/poweroff.html: man/halt.html $(html-alias) @@ -2519,6 +2525,7 @@ EXTRA_DIST += \ man/nss-myhostname.xml \ man/nss-mymachines.xml \ man/nss-resolve.xml \ + man/nss-systemd.xml \ man/os-release.xml \ man/pam_systemd.xml \ man/resolved.conf.xml \ diff --git a/Makefile.am b/Makefile.am index 3d5ce1e2c3..a4241122d5 100644 --- a/Makefile.am +++ b/Makefile.am @@ -5001,6 +5001,27 @@ test_nss_LDADD = \ manual_tests += \ test-nss +# ------------------------------------------------------------------------------ +libnss_systemd_la_SOURCES = \ + src/nss-systemd/nss-systemd.sym \ + src/nss-systemd/nss-systemd.c + +libnss_systemd_la_LDFLAGS = \ + $(AM_LDFLAGS) \ + -module \ + -export-dynamic \ + -avoid-version \ + -shared \ + -shrext .so.2 \ + -Wl,--version-script=$(top_srcdir)/src/nss-systemd/nss-systemd.sym + +libnss_systemd_la_LIBADD = \ + libsystemd-internal.la \ + libbasic.la + +lib_LTLIBRARIES += \ + libnss_systemd.la + # ------------------------------------------------------------------------------ if HAVE_MYHOSTNAME libnss_myhostname_la_SOURCES = \ diff --git a/README b/README index ca8993cb12..19c15a70b0 100644 --- a/README +++ b/README @@ -201,7 +201,7 @@ USERS AND GROUPS: "systemd-coredump" system user and group to exist. NSS: - systemd ships with three NSS modules: + systemd ships with four glibc NSS modules: nss-myhostname resolves the local hostname to locally configured IP addresses, as well as "localhost" to @@ -210,15 +210,22 @@ NSS: nss-resolve enables DNS resolution via the systemd-resolved DNS/LLMNR caching stub resolver "systemd-resolved". - nss-mymachines enables resolution of all local containers - registered with machined to their respective IP addresses. + nss-mymachines enables resolution of all local containers registered + with machined to their respective IP addresses. It also maps UID/GIDs + ranges used by containers to useful names. - To make use of these NSS modules, please add them to the - "hosts: " line in /etc/nsswitch.conf. The "resolve" module - should replace the glibc "dns" module in this file. + nss-systemd enables resolution of all dynamically allocated service + users. (See the DynamicUser= setting in unit files.) - The three modules should be used in the following order: + To make use of these NSS modules, please add them to the "hosts:", + "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve" + module should replace the glibc "dns" module in this file (and don't + worry, it chain-loads the "dns" module if it can't talk to resolved). + The four modules should be used in the following order: + + passwd: compat mymachines systemd + group: compat mymachines systemd hosts: files mymachines resolve myhostname SYSV INIT.D SCRIPTS: diff --git a/man/nss-myhostname.xml b/man/nss-myhostname.xml index a920ec334f..b1daaba02b 100644 --- a/man/nss-myhostname.xml +++ b/man/nss-myhostname.xml @@ -106,8 +106,8 @@ Here is an example /etc/nsswitch.conf file that enables nss-myhostname correctly: -passwd: compat mymachines -group: compat mymachines +passwd: compat mymachines systemd +group: compat mymachines systemd shadow: compat hosts: files mymachines resolve myhostname @@ -138,6 +138,7 @@ netgroup: nis See Also systemd1, + nss-systemd8, nss-resolve8, nss-mymachines8, nsswitch.conf5, diff --git a/man/nss-mymachines.xml b/man/nss-mymachines.xml index ec047449bf..a70119e256 100644 --- a/man/nss-mymachines.xml +++ b/man/nss-mymachines.xml @@ -82,8 +82,8 @@ Here is an example /etc/nsswitch.conf file that enables nss-mymachines correctly: - passwd: compat mymachines -group: compat mymachines + passwd: compat mymachines systemd +group: compat mymachines systemd shadow: compat hosts: files mymachines resolve myhostname @@ -103,6 +103,7 @@ netgroup: nis systemd1, systemd-machined.service8, + nss-systemd8, nss-resolve8, nss-myhostname8, nsswitch.conf5, diff --git a/man/nss-resolve.xml b/man/nss-resolve.xml index d9e56453e8..e6cc1d982a 100644 --- a/man/nss-resolve.xml +++ b/man/nss-resolve.xml @@ -81,8 +81,8 @@ Here is an example /etc/nsswitch.conf file that enables nss-resolve correctly: -passwd: compat mymachines -group: compat mymachines +passwd: compat mymachines systemd +group: compat mymachines systemd shadow: compat hosts: files mymachines resolve myhostname @@ -102,8 +102,9 @@ netgroup: nis systemd1, systemd-resolved8, - nss-mymachines8, + nss-systemd8, nss-myhostname8, + nss-mymachines8, nsswitch.conf5 diff --git a/man/nss-systemd.xml b/man/nss-systemd.xml new file mode 100644 index 0000000000..4228372e51 --- /dev/null +++ b/man/nss-systemd.xml @@ -0,0 +1,107 @@ + + + + + + + + + nss-systemd + systemd + + + + Developer + Lennart + Poettering + lennart@poettering.net + + + + + + nss-systemd + 8 + + + + nss-systemd + libnss_systemd.so.2 + Provide UNIX user and group name resolution for dynamic users and groups. + + + + libnss_systemd.so.2 + + + + Description + + nss-systemd is a plug-in module for the GNU Name Service Switch (NSS) functionality of the + GNU C Library (glibc), providing UNIX user and group name resolution for dynamic users and + groups allocated through the DynamicUser= option in systemd unit files. See + systemd.exec5 for details on + this option. + + To activate the NSS module, add systemd to the lines starting with + passwd: and group: in /etc/nsswitch.conf. + + It is recommended to place systemd after the files or + compat entry of the /etc/nsswitch.conf lines so that + /etc/passwd and /etc/group based mappings take precedence. + + + + Example + + Here is an example /etc/nsswitch.conf file that enables + nss-systemd correctly: + + passwd: compat mymachines systemd +group: compat mymachines systemd +shadow: compat + +hosts: files mymachines resolve myhostname +networks: files + +protocols: db files +services: db files +ethers: db files +rpc: db files + +netgroup: nis + + + + + See Also + + systemd1, + systemd.exec5, + nss-resolve8, + nss-myhostname8, + nss-mymachines8, + nsswitch.conf5, + getent1 + + + + diff --git a/src/core/execute.c b/src/core/execute.c index c186f2a705..26e9cd5339 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -1670,6 +1670,12 @@ static int exec_child( if (context->dynamic_user && dcreds) { + /* Make sure we bypass our own NSS module for any NSS checks */ + if (putenv((char*) "SYSTEMD_NSS_DYNAMIC_BYPASS=1") != 0) { + *exit_status = EXIT_USER; + return -errno; + } + r = dynamic_creds_realize(dcreds, &uid, &gid); if (r < 0) { *exit_status = EXIT_USER; diff --git a/src/nss-systemd/Makefile b/src/nss-systemd/Makefile new file mode 120000 index 0000000000..d0b0e8e008 --- /dev/null +++ b/src/nss-systemd/Makefile @@ -0,0 +1 @@ +../Makefile \ No newline at end of file diff --git a/src/nss-systemd/nss-systemd.c b/src/nss-systemd/nss-systemd.c new file mode 100644 index 0000000000..e7a4393bb0 --- /dev/null +++ b/src/nss-systemd/nss-systemd.c @@ -0,0 +1,332 @@ +/*** + This file is part of systemd. + + Copyright 2016 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see . +***/ + +#include + +#include "sd-bus.h" + +#include "bus-common-errors.h" +#include "env-util.h" +#include "macro.h" +#include "nss-util.h" +#include "signal-util.h" +#include "user-util.h" +#include "util.h" + +NSS_GETPW_PROTOTYPES(systemd); +NSS_GETGR_PROTOTYPES(systemd); + +enum nss_status _nss_systemd_getpwnam_r( + const char *name, + struct passwd *pwd, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; + _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL; + _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + uint32_t translated; + size_t l; + int r; + + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(name); + assert(pwd); + + /* Make sure that we don't go in circles when allocating a dynamic UID by checking our own database */ + if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0) + goto not_found; + + r = sd_bus_open_system(&bus); + if (r < 0) + goto fail; + + r = sd_bus_call_method(bus, + "org.freedesktop.systemd1", + "/org/freedesktop/systemd1", + "org.freedesktop.systemd1.Manager", + "LookupDynamicUserByName", + &error, + &reply, + "s", + name); + if (r < 0) { + if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER)) + goto not_found; + + goto fail; + } + + r = sd_bus_message_read(reply, "u", &translated); + if (r < 0) + goto fail; + + l = strlen(name); + if (buflen < l+1) { + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + memcpy(buffer, name, l+1); + + pwd->pw_name = buffer; + pwd->pw_uid = (uid_t) translated; + pwd->pw_gid = (uid_t) translated; + pwd->pw_gecos = (char*) "Dynamic User"; + pwd->pw_passwd = (char*) "*"; /* locked */ + pwd->pw_dir = (char*) "/"; + pwd->pw_shell = (char*) "/sbin/nologin"; + + *errnop = 0; + return NSS_STATUS_SUCCESS; + +not_found: + *errnop = 0; + return NSS_STATUS_NOTFOUND; + +fail: + *errnop = -r; + return NSS_STATUS_UNAVAIL; +} + +enum nss_status _nss_systemd_getpwuid_r( + uid_t uid, + struct passwd *pwd, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; + _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL; + _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + const char *translated; + size_t l; + int r; + + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + if (!uid_is_valid(uid)) { + r = -EINVAL; + goto fail; + } + + if (uid <= SYSTEM_UID_MAX) + goto not_found; + + if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0) + goto not_found; + + r = sd_bus_open_system(&bus); + if (r < 0) + goto fail; + + r = sd_bus_call_method(bus, + "org.freedesktop.systemd1", + "/org/freedesktop/systemd1", + "org.freedesktop.systemd1.Manager", + "LookupDynamicUserByUID", + &error, + &reply, + "u", + (uint32_t) uid); + if (r < 0) { + if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER)) + goto not_found; + + goto fail; + } + + r = sd_bus_message_read(reply, "s", &translated); + if (r < 0) + goto fail; + + l = strlen(translated) + 1; + if (buflen < l) { + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + memcpy(buffer, translated, l); + + pwd->pw_name = buffer; + pwd->pw_uid = uid; + pwd->pw_gid = uid; + pwd->pw_gecos = (char*) "Dynamic User"; + pwd->pw_passwd = (char*) "*"; /* locked */ + pwd->pw_dir = (char*) "/"; + pwd->pw_shell = (char*) "/sbin/nologin"; + + *errnop = 0; + return NSS_STATUS_SUCCESS; + +not_found: + *errnop = 0; + return NSS_STATUS_NOTFOUND; + +fail: + *errnop = -r; + return NSS_STATUS_UNAVAIL; +} + +enum nss_status _nss_systemd_getgrnam_r( + const char *name, + struct group *gr, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; + _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL; + _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + uint32_t translated; + size_t l; + int r; + + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(name); + assert(gr); + + if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0) + goto not_found; + + r = sd_bus_open_system(&bus); + if (r < 0) + goto fail; + + r = sd_bus_call_method(bus, + "org.freedesktop.systemd1", + "/org/freedesktop/systemd1", + "org.freedesktop.systemd1.Manager", + "LookupDynamicUserByName", + &error, + &reply, + "s", + name); + if (r < 0) { + if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER)) + goto not_found; + + goto fail; + } + + r = sd_bus_message_read(reply, "u", &translated); + if (r < 0) + goto fail; + + l = sizeof(char*) + strlen(name) + 1; + if (buflen < l) { + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + memzero(buffer, sizeof(char*)); + strcpy(buffer + sizeof(char*), name); + + gr->gr_name = buffer + sizeof(char*); + gr->gr_gid = (gid_t) translated; + gr->gr_passwd = (char*) "*"; /* locked */ + gr->gr_mem = (char**) buffer; + + *errnop = 0; + return NSS_STATUS_SUCCESS; + +not_found: + *errnop = 0; + return NSS_STATUS_NOTFOUND; + +fail: + *errnop = -r; + return NSS_STATUS_UNAVAIL; +} + +enum nss_status _nss_systemd_getgrgid_r( + gid_t gid, + struct group *gr, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL; + _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL; + _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; + const char *translated; + size_t l; + int r; + + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + if (!gid_is_valid(gid)) { + r = -EINVAL; + goto fail; + } + + if (gid <= SYSTEM_GID_MAX) + goto not_found; + + if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0) + goto not_found; + + r = sd_bus_open_system(&bus); + if (r < 0) + goto fail; + + r = sd_bus_call_method(bus, + "org.freedesktop.systemd1", + "/org/freedesktop/systemd1", + "org.freedesktop.systemd1.Manager", + "LookupDynamicUserByUID", + &error, + &reply, + "u", + (uint32_t) gid); + if (r < 0) { + if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER)) + goto not_found; + + goto fail; + } + + r = sd_bus_message_read(reply, "s", &translated); + if (r < 0) + goto fail; + + l = sizeof(char*) + strlen(translated) + 1; + if (buflen < l) { + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + memzero(buffer, sizeof(char*)); + strcpy(buffer + sizeof(char*), translated); + + gr->gr_name = buffer + sizeof(char*); + gr->gr_gid = gid; + gr->gr_passwd = (char*) "*"; /* locked */ + gr->gr_mem = (char**) buffer; + + *errnop = 0; + return NSS_STATUS_SUCCESS; + +not_found: + *errnop = 0; + return NSS_STATUS_NOTFOUND; + +fail: + *errnop = -r; + return NSS_STATUS_UNAVAIL; +} diff --git a/src/nss-systemd/nss-systemd.sym b/src/nss-systemd/nss-systemd.sym new file mode 100644 index 0000000000..955078788a --- /dev/null +++ b/src/nss-systemd/nss-systemd.sym @@ -0,0 +1,17 @@ +/*** + This file is part of systemd. + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. +***/ + +{ +global: + _nss_systemd_getpwnam_r; + _nss_systemd_getpwuid_r; + _nss_systemd_getgrnam_r; + _nss_systemd_getgrgid_r; +local: *; +}; -- cgit v1.2.3-54-g00ecf