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If sudo is not set-user-ID root, check for the no_new_privs flag on Linux.

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This flag disables set-user-ID at execve(2) time and may be set by
default for some containers.  GitHub issue #129.
This commit is contained in:
Todd C. Miller
2022-01-09 17:31:06 -07:00
parent 48bc498a6f
commit 2e08db3695
1 changed files with 15 additions and 1 deletions
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16
src/sudo.c
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@@ -32,6 +32,9 @@
#include <sys/wait.h>
#include <sys/resource.h>
#include <sys/socket.h>
#ifdef __linux__
# include <sys/prctl.h>
#endif
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
@@ -318,7 +321,7 @@ main(int argc, char *argv[], char *envp[])
sa.sa_handler = SIG_DFL;
sigaction(WTERMSIG(status), &sa, NULL);
sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys,
WTERMSIG(status) | 128);
WTERMSIG(status) | 128);
kill(getpid(), WTERMSIG(status));
}
sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys,
@@ -899,6 +902,17 @@ sudo_check_suid(const char *sudo)
debug_decl(sudo_check_suid, SUDO_DEBUG_PCOMM);
if (geteuid() != ROOT_UID) {
#if defined(__linux__) && defined(PR_GET_NO_NEW_PRIVS)
/* The no_new_privs flag disables set-user-ID at execve(2) time. */
if (prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0) == 1) {
sudo_warnx(U_("The \"no new privileges\" flag is set, which "
"prevents sudo from running as root."));
sudo_warnx(U_("If sudo is running in a container, you may need "
"to adjust the container configuration to disable the flag."));
exit(EXIT_FAILURE);
}
#endif /* __linux__ && PR_GET_NO_NEW_PRIVS */
/* Search for sudo binary in PATH if not fully qualified. */
qualified = strchr(sudo, '/') != NULL;
if (!qualified) {