Refactor disable_execute() and my_execve() into exec_common.c for
use by sesh.c. This fixes NOEXEC when SELinux is used. Instead of disabling exec in exec_setup(), disable it immediately before executing the command. Adapted from a diff by Arno Schuring.
This commit is contained in:
Todd C. Miller
149
src/exec_common.c
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149
src/exec_common.c
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/*
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* Copyright (c) 2009-2012 Todd C. Miller <Todd.Miller@courtesan.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <config.h>
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#include <sys/types.h>
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#include <sys/param.h>
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#include <stdio.h>
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#ifdef STDC_HEADERS
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# include <stdlib.h>
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# include <stddef.h>
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#else
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# ifdef HAVE_STDLIB_H
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# include <stdlib.h>
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# endif
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#endif /* STDC_HEADERS */
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif /* HAVE_STRING_H */
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#ifdef HAVE_STRINGS_H
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# include <strings.h>
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#endif /* HAVE_STRINGS_H */
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#ifdef HAVE_UNISTD_H
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# include <unistd.h>
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#endif /* HAVE_UNISTD_H */
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#ifdef HAVE_PRIV_SET
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# include <priv.h>
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#endif
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#include <errno.h>
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#include "sudo.h"
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#include "sudo_exec.h"
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/*
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* Disable execution of child processes in the command we are about
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* to run. On systems with privilege sets, we can remove the exec
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* privilege. On other systems we use LD_PRELOAD and the like.
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*/
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static char * const *
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disable_execute(char *const envp[])
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{
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#ifdef _PATH_SUDO_NOEXEC
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char * const *ev;
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char *cp, **nenvp;
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int env_len = 0, env_size = 128;
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#endif /* _PATH_SUDO_NOEXEC */
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debug_decl(disable_execute, SUDO_DEBUG_UTIL)
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#ifdef HAVE_PRIV_SET
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/* Solaris privileges, remove PRIV_PROC_EXEC post-execve. */
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if (priv_set(PRIV_OFF, PRIV_LIMIT, "PRIV_PROC_EXEC", NULL) == 0)
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debug_return_ptr(envp);
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warning(_("unable to remove PRIV_PROC_EXEC from PRIV_LIMIT"));
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#endif /* HAVE_PRIV_SET */
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#ifdef _PATH_SUDO_NOEXEC
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nenvp = emalloc2(env_size, sizeof(char *));
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for (ev = envp; *ev != NULL; ev++) {
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if (env_len + 2 > env_size) {
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env_size += 128;
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nenvp = erealloc3(nenvp, env_size, sizeof(char *));
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}
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/*
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* Prune out existing preloaded libraries.
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* XXX - should save and append instead of replacing.
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*/
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# if defined(__darwin__) || defined(__APPLE__)
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if (strncmp(*ev, "DYLD_INSERT_LIBRARIES=", sizeof("DYLD_INSERT_LIBRARIES=") - 1) == 0)
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continue;
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if (strncmp(*ev, "DYLD_FORCE_FLAT_NAMESPACE=", sizeof("DYLD_INSERT_LIBRARIES=") - 1) == 0)
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continue;
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# elif defined(__osf__) || defined(__sgi)
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if (strncmp(*ev, "_RLD_LIST=", sizeof("_RLD_LIST=") - 1) == 0)
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continue;
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# elif defined(_AIX)
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if (strncmp(*ev, "LDR_PRELOAD=", sizeof("LDR_PRELOAD=") - 1) == 0)
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continue;
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# else
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if (strncmp(*ev, "LD_PRELOAD=", sizeof("LD_PRELOAD=") - 1) == 0)
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continue;
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# endif
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nenvp[env_len++] = *ev;
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}
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/*
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* Preload a noexec file? For a list of LD_PRELOAD-alikes, see
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* http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html
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* XXX - need to support 32-bit and 64-bit variants
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*/
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# if defined(__darwin__) || defined(__APPLE__)
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nenvp[env_len++] = "DYLD_FORCE_FLAT_NAMESPACE=";
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cp = fmt_string("DYLD_INSERT_LIBRARIES", sudo_conf_noexec_path());
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# elif defined(__osf__) || defined(__sgi)
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easprintf(&cp, "_RLD_LIST=%s:DEFAULT", sudo_conf_noexec_path());
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# elif defined(_AIX)
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cp = fmt_string("LDR_PRELOAD", sudo_conf_noexec_path());
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# else
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cp = fmt_string("LD_PRELOAD", sudo_conf_noexec_path());
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# endif
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if (cp == NULL)
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errorx(1, _("unable to allocate memory"));
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nenvp[env_len++] = cp;
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nenvp[env_len] = NULL;
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envp = nenvp;
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#endif /* _PATH_SUDO_NOEXEC */
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debug_return_ptr(envp);
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}
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/*
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* Like execve(2) but falls back to running through /bin/sh
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* ala execvp(3) if we get ENOEXEC.
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*/
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int
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sudo_execve(const char *path, char *const argv[], char *const envp[], int noexec)
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{
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/* Modify the environment as needed to disable further execve(). */
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if (noexec)
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envp = disable_execute(envp);
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execve(path, argv, envp);
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if (errno == ENOEXEC) {
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int argc;
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char **nargv;
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for (argc = 0; argv[argc] != NULL; argc++)
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continue;
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nargv = emalloc2(argc + 2, sizeof(char *));
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nargv[0] = "sh";
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nargv[1] = (char *)path;
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memcpy(nargv + 2, argv + 1, argc * sizeof(char *));
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execve(_PATH_BSHELL, nargv, envp);
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efree(nargv);
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}
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return -1;
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}
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