From 2d6fce8d7c397fe915230b728cb92aa749245e43 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 6 Oct 2016 16:03:01 +0200 Subject: core: leave PAM stub process around with GIDs updated In the process execution code of PID 1, before 096424d1230e0a0339735c51b43949809e972430 the GID settings where changed before invoking PAM, and the UID settings after. After the change both changes are made after the PAM session hooks are run. When invoking PAM we fork once, and leave a stub process around which will invoke the PAM session end hooks when the session goes away. This code previously was dropping the remaining privs (which were precisely the UID). Fix this code to do this correctly again, by really dropping them else (i.e. the GID as well). While we are at it, also fix error logging of this code. Fixes: #4238 --- src/core/execute.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'src/core/execute.c') diff --git a/src/core/execute.c b/src/core/execute.c index 019ff8490b..e4a23ac169 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -843,6 +843,7 @@ static int setup_pam( const char *name, const char *user, uid_t uid, + gid_t gid, const char *tty, char ***env, int fds[], unsigned n_fds) { @@ -948,8 +949,13 @@ static int setup_pam( * and this will make PR_SET_PDEATHSIG work in most cases. * If this fails, ignore the error - but expect sd-pam threads * to fail to exit normally */ + + if (maybe_setgroups(0, NULL) < 0) + log_warning_errno(errno, "Failed to setgroups() in sd-pam: %m"); + if (setresgid(gid, gid, gid) < 0) + log_warning_errno(errno, "Failed to setresgid() in sd-pam: %m"); if (setresuid(uid, uid, uid) < 0) - log_error_errno(r, "Error: Failed to setresuid() in sd-pam: %m"); + log_warning_errno(errno, "Failed to setresuid() in sd-pam: %m"); (void) ignore_signals(SIGPIPE, -1); @@ -2413,7 +2419,7 @@ static int exec_child( } if (context->pam_name && username) { - r = setup_pam(context->pam_name, username, uid, context->tty_path, &accum_env, fds, n_fds); + r = setup_pam(context->pam_name, username, uid, gid, context->tty_path, &accum_env, fds, n_fds); if (r < 0) { *exit_status = EXIT_PAM; return r; -- cgit v1.2.3-54-g00ecf From 97f0e76f18d322d29bcfbc4ab6bb9cd67a1cdd54 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 6 Oct 2016 17:54:12 +0200 Subject: user-util: rework maybe_setgroups() a bit Let's drop the caching of the setgroups /proc field for now. While there's a strict regime in place when it changes states, let's better not cache it since we cannot really be sure we follow that regime correctly. More importantly however, this is not in performance sensitive code, and there's no indication the cache is really beneficial, hence let's drop the caching and make things a bit simpler. Also, while we are at it, rework the error handling a bit, and always return negative errno-style error codes, following our usual coding style. This has the benefit that we can sensible hanld read_one_line_file() errors, without having to updat errno explicitly. --- src/basic/capability-util.c | 5 +++-- src/basic/user-util.c | 49 ++++++++++++++++++++++++++------------------- src/core/execute.c | 10 +++++---- 3 files changed, 37 insertions(+), 27 deletions(-) (limited to 'src/core/execute.c') diff --git a/src/basic/capability-util.c b/src/basic/capability-util.c index f8db6e0212..c3de20a0e8 100644 --- a/src/basic/capability-util.c +++ b/src/basic/capability-util.c @@ -296,8 +296,9 @@ int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) { if (setresgid(gid, gid, gid) < 0) return log_error_errno(errno, "Failed to change group ID: %m"); - if (maybe_setgroups(0, NULL) < 0) - return log_error_errno(errno, "Failed to drop auxiliary groups list: %m"); + r = maybe_setgroups(0, NULL); + if (r < 0) + return log_error_errno(r, "Failed to drop auxiliary groups list: %m"); /* Ensure we keep the permitted caps across the setresuid() */ if (prctl(PR_SET_KEEPCAPS, 1) < 0) diff --git a/src/basic/user-util.c b/src/basic/user-util.c index 16496fccfa..de6c93056e 100644 --- a/src/basic/user-util.c +++ b/src/basic/user-util.c @@ -460,9 +460,11 @@ int get_shell(char **_s) { } int reset_uid_gid(void) { + int r; - if (maybe_setgroups(0, NULL) < 0) - return -errno; + r = maybe_setgroups(0, NULL); + if (r < 0) + return r; if (setresgid(0, 0, 0) < 0) return -errno; @@ -605,25 +607,30 @@ bool valid_home(const char *p) { } int maybe_setgroups(size_t size, const gid_t *list) { - static int cached_can_setgroups = -1; - /* check if setgroups is allowed before we try to drop all the auxiliary groups */ - if (size == 0) { - if (cached_can_setgroups < 0) { - _cleanup_free_ char *setgroups_content = NULL; - int r = read_one_line_file("/proc/self/setgroups", &setgroups_content); - if (r < 0 && errno != ENOENT) - return r; - if (r < 0) { - /* old kernels don't have /proc/self/setgroups, so assume we can use setgroups */ - cached_can_setgroups = true; - } else { - cached_can_setgroups = streq(setgroups_content, "allow"); - if (!cached_can_setgroups) - log_debug("skip setgroups, /proc/self/setgroups is set to 'deny'"); - } - } - if (!cached_can_setgroups) + int r; + + /* Check if setgroups is allowed before we try to drop all the auxiliary groups */ + if (size == 0) { /* Dropping all aux groups? */ + _cleanup_free_ char *setgroups_content = NULL; + bool can_setgroups; + + r = read_one_line_file("/proc/self/setgroups", &setgroups_content); + if (r == -ENOENT) + /* Old kernels don't have /proc/self/setgroups, so assume we can use setgroups */ + can_setgroups = true; + else if (r < 0) + return r; + else + can_setgroups = streq(setgroups_content, "allow"); + + if (!can_setgroups) { + log_debug("Skipping setgroups(), /proc/self/setgroups is set to 'deny'"); return 0; + } } - return setgroups(size, list); + + if (setgroups(size, list) < 0) + return -errno; + + return 0; } diff --git a/src/core/execute.c b/src/core/execute.c index e4a23ac169..d5c4e60796 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -781,9 +781,10 @@ static int enforce_groups(const ExecContext *context, const char *username, gid_ k++; } - if (maybe_setgroups(k, gids) < 0) { + r = maybe_setgroups(k, gids); + if (r < 0) { free(gids); - return -errno; + return r; } free(gids); @@ -950,8 +951,9 @@ static int setup_pam( * If this fails, ignore the error - but expect sd-pam threads * to fail to exit normally */ - if (maybe_setgroups(0, NULL) < 0) - log_warning_errno(errno, "Failed to setgroups() in sd-pam: %m"); + r = maybe_setgroups(0, NULL); + if (r < 0) + log_warning_errno(r, "Failed to setgroups() in sd-pam: %m"); if (setresgid(gid, gid, gid) < 0) log_warning_errno(errno, "Failed to setresgid() in sd-pam: %m"); if (setresuid(uid, uid, uid) < 0) -- cgit v1.2.3-54-g00ecf