upstream commit

Move several subprocess-related functions from various
locations to misc.c. Extend subprocess() to offer a little more control over
stdio disposition.

feedback & ok dtucker@

Upstream-ID: 3573dd7109d13ef9bd3bed93a3deb170fbfce049

1 files changed, 9 insertions, 290 deletions

diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index 1c59b5bb0..0b1e88deb 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.68 2017/06/24 06:34:38 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.69 2017/08/18 05:36:45 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -27,7 +27,6 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/wait.h>
 
 #include <errno.h>
 #include <fcntl.h>
@@ -242,288 +241,6 @@ done:
         return authenticated;
 }
 
-/*
- * Splits 's' into an argument vector. Handles quoted string and basic
- * escape characters (\\, \", \'). Caller must free the argument vector
- * and its members.
- */
-static int
-split_argv(const char *s, int *argcp, char ***argvp)
-{
-        int r = SSH_ERR_INTERNAL_ERROR;
-        int argc = 0, quote, i, j;
-        char *arg, **argv = xcalloc(1, sizeof(*argv));
-
-        *argvp = NULL;
-        *argcp = 0;
-
-        for (i = 0; s[i] != '\0'; i++) {
-                /* Skip leading whitespace */
-                if (s[i] == ' ' || s[i] == '\t')
-                        continue;
-
-                /* Start of a token */
-                quote = 0;
-                if (s[i] == '\\' &&
-                    (s[i + 1] == '\'' || s[i + 1] == '\"' || s[i + 1] == '\\'))
-                        i++;
-                else if (s[i] == '\'' || s[i] == '"')
-                        quote = s[i++];
-
-                argv = xreallocarray(argv, (argc + 2), sizeof(*argv));
-                arg = argv[argc++] = xcalloc(1, strlen(s + i) + 1);
-                argv[argc] = NULL;
-
-                /* Copy the token in, removing escapes */
-                for (j = 0; s[i] != '\0'; i++) {
-                        if (s[i] == '\\') {
-                                if (s[i + 1] == '\'' ||
-                                    s[i + 1] == '\"' ||
-                                    s[i + 1] == '\\') {
-                                        i++; /* Skip '\' */
-                                        arg[j++] = s[i];
-                                } else {
-                                        /* Unrecognised escape */
-                                        arg[j++] = s[i];
-                                }
-                        } else if (quote == 0 && (s[i] == ' ' || s[i] == '\t'))
-                                break; /* done */
-                        else if (quote != 0 && s[i] == quote)
-                                break; /* done */
-                        else
-                                arg[j++] = s[i];
-                }
-                if (s[i] == '\0') {
-                        if (quote != 0) {
-                                /* Ran out of string looking for close quote */
-                                r = SSH_ERR_INVALID_FORMAT;
-                                goto out;
-                        }
-                        break;
-                }
-        }
-        /* Success */
-        *argcp = argc;
-        *argvp = argv;
-        argc = 0;
-        argv = NULL;
-        r = 0;
- out:
-        if (argc != 0 && argv != NULL) {
-                for (i = 0; i < argc; i++)
-                        free(argv[i]);
-                free(argv);
-        }
-        return r;
-}
-
-/*
- * Reassemble an argument vector into a string, quoting and escaping as
- * necessary. Caller must free returned string.
- */
-static char *
-assemble_argv(int argc, char **argv)
-{
-        int i, j, ws, r;
-        char c, *ret;
-        struct sshbuf *buf, *arg;
-
-        if ((buf = sshbuf_new()) == NULL || (arg = sshbuf_new()) == NULL)
-                fatal("%s: sshbuf_new failed", __func__);
-
-        for (i = 0; i < argc; i++) {
-                ws = 0;
-                sshbuf_reset(arg);
-                for (j = 0; argv[i][j] != '\0'; j++) {
-                        r = 0;
-                        c = argv[i][j];
-                        switch (c) {
-                        case ' ':
-                        case '\t':
-                                ws = 1;
-                                r = sshbuf_put_u8(arg, c);
-                                break;
-                        case '\\':
-                        case '\'':
-                        case '"':
-                                if ((r = sshbuf_put_u8(arg, '\\')) != 0)
-                                        break;
-                                /* FALLTHROUGH */
-                        default:
-                                r = sshbuf_put_u8(arg, c);
-                                break;
-                        }
-                        if (r != 0)
-                                fatal("%s: sshbuf_put_u8: %s",
-                                    __func__, ssh_err(r));
-                }
-                if ((i != 0 && (r = sshbuf_put_u8(buf, ' ')) != 0) ||
-                    (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0) ||
-                    (r = sshbuf_putb(buf, arg)) != 0 ||
-                    (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0))
-                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
-        }
-        if ((ret = malloc(sshbuf_len(buf) + 1)) == NULL)
-                fatal("%s: malloc failed", __func__);
-        memcpy(ret, sshbuf_ptr(buf), sshbuf_len(buf));
-        ret[sshbuf_len(buf)] = '\0';
-        sshbuf_free(buf);
-        sshbuf_free(arg);
-        return ret;
-}
-
-/*
- * Runs command in a subprocess. Returns pid on success and a FILE* to the
- * subprocess' stdout or 0 on failure.
- * NB. "command" is only used for logging.
- */
-static pid_t
-subprocess(const char *tag, struct passwd *pw, const char *command,
-    int ac, char **av, FILE **child)
-{
-        FILE *f;
-        struct stat st;
-        int devnull, p[2], i;
-        pid_t pid;
-        char *cp, errmsg[512];
-        u_int envsize;
-        char **child_env;
-
-        *child = NULL;
-
-        debug3("%s: %s command \"%s\" running as %s", __func__,
-            tag, command, pw->pw_name);
-
-        /* Verify the path exists and is safe-ish to execute */
-        if (*av[0] != '/') {
-                error("%s path is not absolute", tag);
-                return 0;
-        }
-        temporarily_use_uid(pw);
-        if (stat(av[0], &st) < 0) {
-                error("Could not stat %s \"%s\": %s", tag,
-                    av[0], strerror(errno));
-                restore_uid();
-                return 0;
-        }
-        if (auth_secure_path(av[0], &st, NULL, 0,
-            errmsg, sizeof(errmsg)) != 0) {
-                error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
-                restore_uid();
-                return 0;
-        }
-
-        /*
-         * Run the command; stderr is left in place, stdout is the
-         * authorized_keys output.
-         */
-        if (pipe(p) != 0) {
-                error("%s: pipe: %s", tag, strerror(errno));
-                restore_uid();
-                return 0;
-        }
-
-        /*
-         * Don't want to call this in the child, where it can fatal() and
-         * run cleanup_exit() code.
-         */
-        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++)
-                        signal(i, SIG_DFL);
-
-                if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
-                        error("%s: open %s: %s", tag, _PATH_DEVNULL,
-                            strerror(errno));
-                        _exit(1);
-                }
-                /* Keep stderr around a while longer to catch errors */
-                if (dup2(devnull, STDIN_FILENO) == -1 ||
-                    dup2(p[1], 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) != 0) {
-                        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) != 0) {
-                        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 (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 ((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("%s: %s pid %ld", __func__, tag, (long)pid);
-        *child = f;
-        return pid;
-}
-
-/* Returns 0 if pid exited cleanly, non-zero otherwise */
-static int
-exited_cleanly(pid_t pid, const char *tag, const char *cmd)
-{
-        int status;
-
-        while (waitpid(pid, &status, 0) == -1) {
-                if (errno != EINTR) {
-                        error("%s: waitpid: %s", tag, strerror(errno));
-                        return -1;
-                }
-        }
-        if (WIFSIGNALED(status)) {
-                error("%s %s exited on signal %d", tag, cmd, WTERMSIG(status));
-                return -1;
-        } else if (WEXITSTATUS(status) != 0) {
-                error("%s %s failed, status %d", tag, cmd, WEXITSTATUS(status));
-                return -1;
-        }
-        return 0;
-}
-
 static int
 match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 {
@@ -656,7 +373,7 @@ match_principals_command(struct passwd *user_pw, const struct sshkey *key)
         }
 
         /* Turn the command into an argument vector */
-        if (split_argv(options.authorized_principals_command, &ac, &av) != 0) {
+        if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
                 error("AuthorizedPrincipalsCommand \"%s\" contains "
                     "invalid quotes", command);
                 goto out;
@@ -705,10 +422,11 @@ match_principals_command(struct passwd *user_pw, const struct sshkey *key)
                 av[i] = tmp;
         }
         /* Prepare a printable command for logs, etc. */
-        command = assemble_argv(ac, av);
+        command = argv_assemble(ac, av);
 
         if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command,
-            ac, av, &f)) == 0)
+            ac, av, &f,
+            SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
                 goto out;
 
         uid_swapped = 1;
@@ -996,7 +714,7 @@ user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key)
         }
 
         /* Turn the command into an argument vector */
-        if (split_argv(options.authorized_keys_command, &ac, &av) != 0) {
+        if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
                 error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
                     command);
                 goto out;
@@ -1020,7 +738,7 @@ user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key)
                 av[i] = tmp;
         }
         /* Prepare a printable command for logs, etc. */
-        command = assemble_argv(ac, av);
+        command = argv_assemble(ac, av);
 
         /*
          * If AuthorizedKeysCommand was run without arguments
@@ -1037,7 +755,8 @@ user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key)
         }
 
         if ((pid = subprocess("AuthorizedKeysCommand", pw, command,
-            ac, av, &f)) == 0)
+            ac, av, &f,
+            SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
                 goto out;
 
         uid_swapped = 1;