From 12631c59bb36abd420c9f2752131fcf2a4c6187d Mon Sep 17 00:00:00 2001 From: "Nicholas J. Kain" Date: Fri, 25 Feb 2022 06:43:42 -0500 Subject: [PATCH] Update to latest nk/exec.c; see ncron repo for changes. Notably, nk_generate_env() no longer calls malloc(). --- nk/exec.c | 106 +++++++++++++++++++++++++++--------------------------- nk/exec.h | 12 +++++-- scriptd.c | 26 +++----------- 3 files changed, 67 insertions(+), 77 deletions(-) diff --git a/nk/exec.c b/nk/exec.c index 108a2c0..b49dc1c 100644 --- a/nk/exec.c +++ b/nk/exec.c @@ -1,4 +1,4 @@ -// Copyright 2003-2018 Nicholas J. Kain +// Copyright 2003-2022 Nicholas J. Kain // SPDX-License-Identifier: MIT #include #include @@ -26,13 +26,14 @@ #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 MAX_ARGS 256 -#define MAX_ARGBUF 4096 +#define MAX_ARGBUF 16384 +#define MAX_PWBUF 16384 #define NK_GEN_ENV(GEN_STR, ...) do { \ if (env_offset >= envlen) return -3; \ ssize_t snlen = snprintf(envbuf, envbuflen, GEN_STR, __VA_ARGS__); \ - if (snlen < 0 || (size_t)snlen >= envbuflen) return -2; \ - env[env_offset++] = envbuf; envbuf += snlen; envbuflen -= (size_t)snlen; \ + if (snlen < 0 || (size_t)snlen > envbuflen) return -2; \ + xe->env[env_offset++] = envbuf; envbuf += snlen; envbuflen -= (size_t)snlen; \ } while (0) /* @@ -51,54 +52,30 @@ * -3 if there is not enough space in env for the generated environment * -4 if chdir to homedir or rootdir 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, - char *env[], size_t envlen, char *envbuf, size_t envbuflen) +int nk_generate_env(struct nk_exec_env *xe, uid_t uid, const char *chroot_path, const char *path_var) { - char pw_strs[4096]; - struct passwd pw_s; - struct passwd *pw; - char *pw_buf = NULL; - int ret = 0, pwr; + char pwbuf[MAX_PWBUF]; + struct passwd pw_s, *pw; -getpwagain0: - pwr = getpwuid_r(uid, &pw_s, pw_strs, sizeof pw_strs, &pw); - if (pw == NULL) { - if (pwr == 0) { ret = -1; goto out; } - if (pwr == EINTR) goto getpwagain0; - if (pwr == ERANGE) { - size_t pwlen = (sizeof pw_strs >> 1) * 3; - for (;;) { - if (pw_buf) free(pw_buf); - 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 - } + for (;;) { + int r = getpwuid_r(uid, &pw_s, pwbuf, sizeof pwbuf, &pw); + if (!r) { + if (pw == NULL) return -1; + break; + } else { + if (r == EINTR) continue; + if (r == ERANGE) return -6; + return -5; } - ret = -5; goto out; } - if (pwr != 0) { ret = -5; goto out; } size_t env_offset = 0; - if (envlen-- < 1) { // So we don't have to account for the terminal NULL - ret = -3; - goto out; - } + size_t envlen = sizeof xe->env / sizeof xe->env[0]; + char *envbuf = xe->envbuf; + 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("USER=%s", pw->pw_name); @@ -108,18 +85,43 @@ getpwagain: 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("PWD=%s", !chroot_path ? pw->pw_dir : "/"); - if (chroot_path && chroot(chroot_path)) { ret = -4; goto out; } - if (chdir(chroot_path ? chroot_path : "/")) { ret = -4; goto out; } + if (chroot_path && chroot(chroot_path)) return -4; + if (chdir(chroot_path ? chroot_path : "/")) return -4; - env[env_offset] = 0; -out: - free(pw_buf); - return ret; + xe->env[env_offset] = 0; + return 0; } +#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 { \ 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"; \ safe_write(STDERR_FILENO, errstr, sizeof errstr); \ _Exit(EXIT_FAILURE); \ diff --git a/nk/exec.h b/nk/exec.h index e2d97c4..ecbbff7 100644 --- a/nk/exec.h +++ b/nk/exec.h @@ -1,10 +1,16 @@ -// Copyright 2003-2016 Nicholas J. Kain +// Copyright 2003-2022 Nicholas J. Kain // SPDX-License-Identifier: MIT #ifndef NCM_EXEC_H_ #define NCM_EXEC_H_ -int nk_generate_env(uid_t uid, const char *chroot_path, const char *path_var, - char *env[], size_t envlen, char *envbuf, size_t envbuflen); +struct nk_exec_env +{ + 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)) nk_execute(const char *command, const char *args, char * const envp[]) ; diff --git a/scriptd.c b/scriptd.c index 148c588..6d60057 100644 --- a/scriptd.c +++ b/scriptd.c @@ -17,9 +17,6 @@ #include "ndhc.h" #include "sys.h" -#define MAX_ENVBUF 2048 -#define MAX_CENV 50 - bool valid_script_file = false; // Runs the 'script_file'-specified script. Called from ndhc process. @@ -36,30 +33,15 @@ void request_scriptd_run(void) static void run_script(void) { - char *env[MAX_CENV]; - char envbuf[MAX_ENVBUF]; + struct nk_exec_env xe; switch ((int)fork()) { 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) { - static const char errstr[] = "exec: failed to generate environment - "; - 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); + nk_generate_env_print_error(r); exit(EXIT_FAILURE); } - nk_execute(script_file, NULL, env); + nk_execute(script_file, NULL, xe.env); } case -1: { static const char errstr[] = "exec: fork failed\n";