diff options
| -rw-r--r-- | auth.c | 154 | ||||
| -rw-r--r-- | auth.h | 8 | ||||
| -rw-r--r-- | auth2-pubkey.c | 12 | ||||
| -rw-r--r-- | misc.c | 171 | ||||
| -rw-r--r-- | misc.h | 12 |
5 files changed, 190 insertions, 167 deletions
@@ -1,4 +1,4 @@ -/* $OpenBSD: auth.c,v 1.150 2020/12/20 23:36:51 djm Exp $ */ +/* $OpenBSD: auth.c,v 1.151 2020/12/22 00:12:22 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * @@ -841,158 +841,6 @@ auth_get_canonical_hostname(struct ssh *ssh, int use_dns) } } -/* - * Runs command in a subprocess with a minimal environment. - * Returns pid on success, 0 on failure. - * The child stdout and stderr maybe captured, left attached or sent to - * /dev/null depending on the contents of flags. - * "tag" is prepended to log messages. - * NB. "command" is only used for logging; the actual command executed is - * av[0]. - */ -pid_t -subprocess(const char *tag, struct passwd *pw, const char *command, - int ac, char **av, FILE **child, u_int flags) -{ - FILE *f = NULL; - struct stat st; - int fd, devnull, p[2], i; - pid_t pid; - char *cp, errmsg[512]; - u_int envsize; - char **child_env; - - if (child != NULL) - *child = NULL; - - debug3_f("%s command \"%s\" running as %s (flags 0x%x)", - tag, command, pw->pw_name, flags); - - /* Check consistency */ - if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && - (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { - error_f("inconsistent flags"); - return 0; - } - if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { - error_f("inconsistent flags/output"); - return 0; - } - - /* - * If executing an explicit binary, then verify the it exists - * and appears safe-ish to execute - */ - if (!path_absolute(av[0])) { - error("%s path is not absolute", tag); - return 0; - } - temporarily_use_uid(pw); - if (stat(av[0], &st) == -1) { - error("Could not stat %s \"%s\": %s", tag, - av[0], strerror(errno)); - restore_uid(); - return 0; - } - if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { - error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); - restore_uid(); - return 0; - } - /* Prepare to keep the child's stdout if requested */ - if (pipe(p) == -1) { - error("%s: pipe: %s", tag, strerror(errno)); - restore_uid(); - return 0; - } - restore_uid(); - - switch ((pid = fork())) { - case -1: /* error */ - error("%s: fork: %s", tag, strerror(errno)); - close(p[0]); - close(p[1]); - return 0; - case 0: /* child */ - /* Prepare a minimal environment for the child. */ - envsize = 5; - child_env = xcalloc(sizeof(*child_env), envsize); - child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); - child_set_env(&child_env, &envsize, "USER", pw->pw_name); - child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); - child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); - if ((cp = getenv("LANG")) != NULL) - child_set_env(&child_env, &envsize, "LANG", cp); - - for (i = 0; i < NSIG; i++) - ssh_signal(i, SIG_DFL); - - if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { - error("%s: open %s: %s", tag, _PATH_DEVNULL, - strerror(errno)); - _exit(1); - } - if (dup2(devnull, STDIN_FILENO) == -1) { - error("%s: dup2: %s", tag, strerror(errno)); - _exit(1); - } - - /* Set up stdout as requested; leave stderr in place for now. */ - fd = -1; - if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) - fd = p[1]; - else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) - fd = devnull; - if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { - error("%s: dup2: %s", tag, strerror(errno)); - _exit(1); - } - closefrom(STDERR_FILENO + 1); - - /* Don't use permanently_set_uid() here to avoid fatal() */ - if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) { - error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, - strerror(errno)); - _exit(1); - } - if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) { - error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, - strerror(errno)); - _exit(1); - } - /* stdin is pointed to /dev/null at this point */ - if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && - dup2(STDIN_FILENO, STDERR_FILENO) == -1) { - error("%s: dup2: %s", tag, strerror(errno)); - _exit(1); - } - - execve(av[0], av, child_env); - error("%s exec \"%s\": %s", tag, command, strerror(errno)); - _exit(127); - default: /* parent */ - break; - } - - close(p[1]); - if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) - close(p[0]); - else if ((f = fdopen(p[0], "r")) == NULL) { - error("%s: fdopen: %s", tag, strerror(errno)); - close(p[0]); - /* Don't leave zombie child */ - kill(pid, SIGTERM); - while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) - ; - return 0; - } - /* Success */ - debug3_f("%s pid %ld", tag, (long)pid); - if (child != NULL) - *child = f; - return pid; -} - /* These functions link key/cert options to the auth framework */ /* Log sshauthopt options locally and (optionally) for remote transmission */ @@ -1,4 +1,4 @@ -/* $OpenBSD: auth.h,v 1.100 2019/09/06 05:23:55 djm Exp $ */ +/* $OpenBSD: auth.h,v 1.101 2020/12/22 00:12:22 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. @@ -225,12 +225,6 @@ void auth_debug_reset(void); struct passwd *fakepw(void); -#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */ -#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */ -#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */ -pid_t subprocess(const char *, struct passwd *, - const char *, int, char **, FILE **, u_int flags); - int sys_auth_passwd(struct ssh *, const char *); #if defined(KRB5) && !defined(HEIMDAL) diff --git a/auth2-pubkey.c b/auth2-pubkey.c index 307afa56..14863cbf 100644 --- a/auth2-pubkey.c +++ b/auth2-pubkey.c @@ -1,4 +1,4 @@ -/* $OpenBSD: auth2-pubkey.c,v 1.102 2020/12/17 23:28:50 djm Exp $ */ +/* $OpenBSD: auth2-pubkey.c,v 1.103 2020/12/22 00:12:22 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * @@ -530,9 +530,10 @@ match_principals_command(struct ssh *ssh, struct passwd *user_pw, /* Prepare a printable command for logs, etc. */ command = argv_assemble(ac, av); - if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command, + if ((pid = subprocess("AuthorizedPrincipalsCommand", command, ac, av, &f, - SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) + SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, + runas_pw, temporarily_use_uid, restore_uid)) == 0) goto out; uid_swapped = 1; @@ -968,9 +969,10 @@ user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw, xasprintf(&command, "%s %s", av[0], av[1]); } - if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command, + if ((pid = subprocess("AuthorizedKeysCommand", command, ac, av, &f, - SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) + SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, + runas_pw, temporarily_use_uid, restore_uid)) == 0) goto out; uid_swapped = 1; @@ -1,4 +1,4 @@ -/* $OpenBSD: misc.c,v 1.156 2020/11/27 00:49:58 djm Exp $ */ +/* $OpenBSD: misc.c,v 1.157 2020/12/22 00:12:22 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * Copyright (c) 2005-2020 Damien Miller. All rights reserved. @@ -2479,3 +2479,172 @@ stdfd_devnull(int do_stdin, int do_stdout, int do_stderr) close(devnull); return ret; } + +/* + * Runs command in a subprocess with a minimal environment. + * Returns pid on success, 0 on failure. + * The child stdout and stderr maybe captured, left attached or sent to + * /dev/null depending on the contents of flags. + * "tag" is prepended to log messages. + * NB. "command" is only used for logging; the actual command executed is + * av[0]. + */ +pid_t +subprocess(const char *tag, const char *command, + int ac, char **av, FILE **child, u_int flags, + struct passwd *pw, privdrop_fn *drop_privs, privrestore_fn *restore_privs) +{ + FILE *f = NULL; + struct stat st; + int fd, devnull, p[2], i; + pid_t pid; + char *cp, errmsg[512]; + u_int nenv = 0; + char **env = NULL; + + /* If dropping privs, then must specify user and restore function */ + if (drop_privs != NULL && (pw == NULL || restore_privs == NULL)) { + error("%s: inconsistent arguments", tag); /* XXX fatal? */ + return 0; + } + if (pw == NULL && (pw = getpwuid(getuid())) == NULL) { + error("%s: no user for current uid", tag); + return 0; + } + if (child != NULL) + *child = NULL; + + debug3_f("%s command \"%s\" running as %s (flags 0x%x)", + tag, command, pw->pw_name, flags); + + /* Check consistency */ + if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && + (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { + error_f("inconsistent flags"); + return 0; + } + if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { + error_f("inconsistent flags/output"); + return 0; + } + + /* + * If executing an explicit binary, then verify the it exists + * and appears safe-ish to execute + */ + if (!path_absolute(av[0])) { + error("%s path is not absolute", tag); + return 0; + } + if (drop_privs != NULL) + drop_privs(pw); + if (stat(av[0], &st) == -1) { + error("Could not stat %s \"%s\": %s", tag, + av[0], strerror(errno)); + goto restore_return; + } + if ((flags & SSH_SUBPROCESS_UNSAFE_PATH) == 0 && + safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { + error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); + goto restore_return; + } + /* Prepare to keep the child's stdout if requested */ + if (pipe(p) == -1) { + error("%s: pipe: %s", tag, strerror(errno)); + restore_return: + if (restore_privs != NULL) + restore_privs(); + return 0; + } + if (restore_privs != NULL) + restore_privs(); + + switch ((pid = fork())) { + case -1: /* error */ + error("%s: fork: %s", tag, strerror(errno)); + close(p[0]); + close(p[1]); + return 0; + case 0: /* child */ + /* Prepare a minimal environment for the child. */ + if ((flags & SSH_SUBPROCESS_PRESERVE_ENV) == 0) { + nenv = 5; + env = xcalloc(sizeof(*env), nenv); + child_set_env(&env, &nenv, "PATH", _PATH_STDPATH); + child_set_env(&env, &nenv, "USER", pw->pw_name); + child_set_env(&env, &nenv, "LOGNAME", pw->pw_name); + child_set_env(&env, &nenv, "HOME", pw->pw_dir); + if ((cp = getenv("LANG")) != NULL) + child_set_env(&env, &nenv, "LANG", cp); + } + + for (i = 0; i < NSIG; i++) + ssh_signal(i, SIG_DFL); + + if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { + error("%s: open %s: %s", tag, _PATH_DEVNULL, + strerror(errno)); + _exit(1); + } + if (dup2(devnull, STDIN_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + + /* Set up stdout as requested; leave stderr in place for now. */ + fd = -1; + if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) + fd = p[1]; + else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) + fd = devnull; + if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + closefrom(STDERR_FILENO + 1); + + if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) { + error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, + strerror(errno)); + _exit(1); + } + if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) { + error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, + strerror(errno)); + _exit(1); + } + /* stdin is pointed to /dev/null at this point */ + if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && + dup2(STDIN_FILENO, STDERR_FILENO) == -1) { + error("%s: dup2: %s", tag, strerror(errno)); + _exit(1); + } + if (env != NULL) + execve(av[0], av, env); + else + execv(av[0], av); + error("%s %s \"%s\": %s", tag, env == NULL ? "execv" : "execve", + command, strerror(errno)); + _exit(127); + default: /* parent */ + break; + } + + close(p[1]); + if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) + close(p[0]); + else if ((f = fdopen(p[0], "r")) == NULL) { + error("%s: fdopen: %s", tag, strerror(errno)); + close(p[0]); + /* Don't leave zombie child */ + kill(pid, SIGTERM); + while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) + ; + return 0; + } + /* Success */ + debug3_f("%s pid %ld", tag, (long)pid); + if (child != NULL) + *child = f; + return pid; +} @@ -1,4 +1,4 @@ -/* $OpenBSD: misc.h,v 1.90 2020/11/27 00:49:58 djm Exp $ */ +/* $OpenBSD: misc.h,v 1.91 2020/12/22 00:12:22 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -99,6 +99,16 @@ void sock_set_v6only(int); struct passwd *pwcopy(struct passwd *); const char *ssh_gai_strerror(int); +typedef void privdrop_fn(struct passwd *); +typedef void privrestore_fn(void); +#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */ +#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */ +#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */ +#define SSH_SUBPROCESS_UNSAFE_PATH (1<<3) /* Don't check for safe cmd */ +#define SSH_SUBPROCESS_PRESERVE_ENV (1<<4) /* Keep parent environment */ +pid_t subprocess(const char *, const char *, int, char **, FILE **, u_int, + struct passwd *, privdrop_fn *, privrestore_fn *); + typedef struct arglist arglist; struct arglist { char **list; |