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Update to latest nk/exec.c; see ncron repo for changes.

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Notably, nk_generate_env() no longer calls malloc().
This commit is contained in:
Nicholas J. Kain 2022-02-25 06:43:42 -05:00
parent 7572e2eb8b
commit 12631c59bb
3 changed files with 67 additions and 77 deletions
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106
nk/exec.c
View File

@ -1,4 +1,4 @@
// Copyright 2003-2018 Nicholas J. Kain <njkain at gmail dot com> // Copyright 2003-2022 Nicholas J. Kain <njkain at gmail dot com>
// SPDX-License-Identifier: MIT // SPDX-License-Identifier: MIT
#include <sys/types.h> #include <sys/types.h>
#include <stdbool.h> #include <stdbool.h>
@ -26,13 +26,14 @@
#define DEFAULT_ROOT_PATH "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin" #define DEFAULT_ROOT_PATH "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"
#define DEFAULT_PATH "/bin:/usr/bin:/usr/local/bin" #define DEFAULT_PATH "/bin:/usr/bin:/usr/local/bin"
#define MAX_ARGS 256 #define MAX_ARGS 256
#define MAX_ARGBUF 4096 #define MAX_ARGBUF 16384
#define MAX_PWBUF 16384
#define NK_GEN_ENV(GEN_STR, ...) do { \ #define NK_GEN_ENV(GEN_STR, ...) do { \
if (env_offset >= envlen) return -3; \ if (env_offset >= envlen) return -3; \
ssize_t snlen = snprintf(envbuf, envbuflen, GEN_STR, __VA_ARGS__); \ ssize_t snlen = snprintf(envbuf, envbuflen, GEN_STR, __VA_ARGS__); \
if (snlen < 0 || (size_t)snlen >= envbuflen) return -2; \ if (snlen < 0 || (size_t)snlen > envbuflen) return -2; \
env[env_offset++] = envbuf; envbuf += snlen; envbuflen -= (size_t)snlen; \ xe->env[env_offset++] = envbuf; envbuf += snlen; envbuflen -= (size_t)snlen; \
} while (0) } while (0)
/* /*
@ -51,54 +52,30 @@
* -3 if there is not enough space in env for the generated environment * -3 if there is not enough space in env for the generated environment
* -4 if chdir to homedir or rootdir failed * -4 if chdir to homedir or rootdir failed
* -5 if oom or i/o failed * -5 if oom or i/o failed
* -6 if MAX_PWBUF is too small
*/ */
int nk_generate_env(uid_t uid, const char *chroot_path, const char *path_var, int nk_generate_env(struct nk_exec_env *xe, uid_t uid, const char *chroot_path, const char *path_var)
char *env[], size_t envlen, char *envbuf, size_t envbuflen)
{ {
char pw_strs[4096]; char pwbuf[MAX_PWBUF];
struct passwd pw_s; struct passwd pw_s, *pw;
struct passwd *pw;
char *pw_buf = NULL;
int ret = 0, pwr;
getpwagain0: for (;;) {
pwr = getpwuid_r(uid, &pw_s, pw_strs, sizeof pw_strs, &pw); int r = getpwuid_r(uid, &pw_s, pwbuf, sizeof pwbuf, &pw);
if (pw == NULL) { if (!r) {
if (pwr == 0) { ret = -1; goto out; } if (pw == NULL) return -1;
if (pwr == EINTR) goto getpwagain0; break;
if (pwr == ERANGE) { } else {
size_t pwlen = (sizeof pw_strs >> 1) * 3; if (r == EINTR) continue;
for (;;) { if (r == ERANGE) return -6;
if (pw_buf) free(pw_buf); return -5;
pw_buf = malloc(pwlen);
if (!pw_buf) { ret = -5; goto out; }
getpwagain:
pwr = getpwuid_r(uid, &pw_s, pw_buf, pwlen, &pw);
if (pw == NULL) {
if (pwr == 0) { ret = -1; goto out; }
if (pwr == EINTR) goto getpwagain;
if (pwr == ERANGE) {
size_t oldpwlen = pwlen;
pwlen = (pwlen >> 1) * 3;
if (pwlen > oldpwlen) continue;
else { // overflowed
ret = -5; goto out;
}
}
ret = -5; goto out;
}
break; // the pwr != 0 check below applies here
}
} }
ret = -5; goto out;
} }
if (pwr != 0) { ret = -5; goto out; }
size_t env_offset = 0; size_t env_offset = 0;
if (envlen-- < 1) { // So we don't have to account for the terminal NULL size_t envlen = sizeof xe->env / sizeof xe->env[0];
ret = -3; char *envbuf = xe->envbuf;
goto out; size_t envbuflen = sizeof xe->envbuf;
} if (envlen-- < 1) return -3; // So we don't have to account for the terminal NULL
NK_GEN_ENV("UID=%i", uid); NK_GEN_ENV("UID=%i", uid);
NK_GEN_ENV("USER=%s", pw->pw_name); NK_GEN_ENV("USER=%s", pw->pw_name);
@ -108,18 +85,43 @@ getpwagain:
NK_GEN_ENV("SHELL=%s", pw->pw_shell); NK_GEN_ENV("SHELL=%s", pw->pw_shell);
NK_GEN_ENV("PATH=%s", path_var ? path_var : (uid > 0 ? DEFAULT_PATH : DEFAULT_ROOT_PATH)); NK_GEN_ENV("PATH=%s", path_var ? path_var : (uid > 0 ? DEFAULT_PATH : DEFAULT_ROOT_PATH));
NK_GEN_ENV("PWD=%s", !chroot_path ? pw->pw_dir : "/"); NK_GEN_ENV("PWD=%s", !chroot_path ? pw->pw_dir : "/");
if (chroot_path && chroot(chroot_path)) { ret = -4; goto out; } if (chroot_path && chroot(chroot_path)) return -4;
if (chdir(chroot_path ? chroot_path : "/")) { ret = -4; goto out; } if (chdir(chroot_path ? chroot_path : "/")) return -4;
env[env_offset] = 0; xe->env[env_offset] = 0;
out: return 0;
free(pw_buf);
return ret;
} }
#define ERRSTR0 "exec: failed to generate environment - (?) unknown error\n"
#define ERRSTR1 "exec: failed to generate environment - (-1) account for uid does not exist\n"
#define ERRSTR2 "exec: failed to generate environment - (-2) not enough space in envbuf\n"
#define ERRSTR3 "exec: failed to generate environment - (-3) not enough space in env\n"
#define ERRSTR4 "exec: failed to generate environment - (-4) chdir to homedir or rootdir failed\n"
#define ERRSTR5 "exec: failed to generate environment - (-5) oom or i/o error\n"
#define ERRSTR6 "exec: failed to generate environment - (-6) MAX_PWBUF is too small\n"
void nk_generate_env_print_error(int err)
{
switch (err) {
default: safe_write(STDERR_FILENO, ERRSTR0, sizeof ERRSTR0); break;
case -1: safe_write(STDERR_FILENO, ERRSTR1, sizeof ERRSTR1); break;
case -2: safe_write(STDERR_FILENO, ERRSTR2, sizeof ERRSTR2); break;
case -3: safe_write(STDERR_FILENO, ERRSTR3, sizeof ERRSTR3); break;
case -4: safe_write(STDERR_FILENO, ERRSTR4, sizeof ERRSTR4); break;
case -5: safe_write(STDERR_FILENO, ERRSTR5, sizeof ERRSTR5); break;
case -6: safe_write(STDERR_FILENO, ERRSTR6, sizeof ERRSTR6); break;
}
}
#undef ERRSTR0
#undef ERRSTR1
#undef ERRSTR2
#undef ERRSTR3
#undef ERRSTR4
#undef ERRSTR5
#undef ERRSTR6
#define NK_GEN_ARG(GEN_STR, ...) do { \ #define NK_GEN_ARG(GEN_STR, ...) do { \
ssize_t snlen = snprintf(argbuf, argbuflen, GEN_STR, __VA_ARGS__); \ ssize_t snlen = snprintf(argbuf, argbuflen, GEN_STR, __VA_ARGS__); \
if (snlen < 0 || (size_t)snlen >= argbuflen) { \ if (snlen < 0 || (size_t)snlen > argbuflen) { \
static const char errstr[] = "nk_execute: constructing argument list failed\n"; \ static const char errstr[] = "nk_execute: constructing argument list failed\n"; \
safe_write(STDERR_FILENO, errstr, sizeof errstr); \ safe_write(STDERR_FILENO, errstr, sizeof errstr); \
_Exit(EXIT_FAILURE); \ _Exit(EXIT_FAILURE); \

12
nk/exec.h
View File

@ -1,10 +1,16 @@
// Copyright 2003-2016 Nicholas J. Kain <njkain at gmail dot com> // Copyright 2003-2022 Nicholas J. Kain <njkain at gmail dot com>
// SPDX-License-Identifier: MIT // SPDX-License-Identifier: MIT
#ifndef NCM_EXEC_H_ #ifndef NCM_EXEC_H_
#define NCM_EXEC_H_ #define NCM_EXEC_H_
int nk_generate_env(uid_t uid, const char *chroot_path, const char *path_var, struct nk_exec_env
char *env[], size_t envlen, char *envbuf, size_t envbuflen); {
char *env[32];
char envbuf[4096];
};
int nk_generate_env(struct nk_exec_env *xe, uid_t uid, const char *chroot_path, const char *path_var);
void nk_generate_env_print_error(int err);
void __attribute__((noreturn)) void __attribute__((noreturn))
nk_execute(const char *command, const char *args, char * const envp[]) ; nk_execute(const char *command, const char *args, char * const envp[]) ;

26
scriptd.c
View File

@ -17,9 +17,6 @@
#include "ndhc.h" #include "ndhc.h"
#include "sys.h" #include "sys.h"
#define MAX_ENVBUF 2048
#define MAX_CENV 50
bool valid_script_file = false; bool valid_script_file = false;
// Runs the 'script_file'-specified script. Called from ndhc process. // Runs the 'script_file'-specified script. Called from ndhc process.
@ -36,30 +33,15 @@ void request_scriptd_run(void)
static void run_script(void) static void run_script(void)
{ {
char *env[MAX_CENV]; struct nk_exec_env xe;
char envbuf[MAX_ENVBUF];
switch ((int)fork()) { switch ((int)fork()) {
case 0: { case 0: {
int r = nk_generate_env(0, NULL, NULL, env, MAX_CENV, envbuf, sizeof envbuf); int r = nk_generate_env(&xe, 0, NULL, NULL);
if (r < 0) { if (r < 0) {
static const char errstr[] = "exec: failed to generate environment - "; nk_generate_env_print_error(r);
safe_write(STDERR_FILENO, errstr, sizeof errstr);
static const char errstr0[] = "(?) unknown error";
static const char errstr1[] = "(-1) account for uid does not exist";
static const char errstr2[] = "(-2) not enough space in envbuf";
static const char errstr3[] = "(-3) not enough space in env";
static const char errstr4[] = "(-4) chdir to homedir or rootdir failed";
switch (r) {
default: safe_write(STDERR_FILENO, errstr0, sizeof errstr0); break;
case -1: safe_write(STDERR_FILENO, errstr1, sizeof errstr1); break;
case -2: safe_write(STDERR_FILENO, errstr2, sizeof errstr2); break;
case -3: safe_write(STDERR_FILENO, errstr3, sizeof errstr3); break;
case -4: safe_write(STDERR_FILENO, errstr4, sizeof errstr4); break;
}
safe_write(STDERR_FILENO, "\n", 1);
exit(EXIT_FAILURE); exit(EXIT_FAILURE);
} }
nk_execute(script_file, NULL, env); nk_execute(script_file, NULL, xe.env);
} }
case -1: { case -1: {
static const char errstr[] = "exec: fork failed\n"; static const char errstr[] = "exec: fork failed\n";