Adding upstream version 1.9.15p5.upstream/1.9.15p5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 538 insertions, 0 deletions

diff --git a/src/edit_open.c b/src/edit_open.c
new file mode 100644
index 0000000..2fa58f5
--- /dev/null
+++ b/src/edit_open.c
@@ -0,0 +1,538 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2015-2021 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <fcntl.h>
+
+#include <sudo.h>
+#include <sudo_edit.h>
+
+#if defined(HAVE_SETRESUID) || defined(HAVE_SETREUID) || defined(HAVE_SETEUID)
+
+static int
+switch_user_int(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups,
+    bool nonfatal)
+{
+    int serrno = errno;
+    int ret = -1;
+    debug_decl(switch_user, SUDO_DEBUG_EDIT);
+
+    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+	"set uid:gid to %u:%u(%u)", (unsigned int)euid, (unsigned int)egid,
+	ngroups > 0 ? (unsigned int)groups[0] : (unsigned int)egid);
+
+    /* When restoring root, change euid first; otherwise change it last. */
+    if (euid == ROOT_UID) {
+	if (seteuid(ROOT_UID) != 0) {
+	    if (nonfatal)
+		goto done;
+	    sudo_fatal("seteuid(ROOT_UID)");
+	}
+    }
+    if (setegid(egid) != 0) {
+	if (nonfatal)
+	    goto done;
+	sudo_fatal("setegid(%d)", (int)egid);
+    }
+    if (ngroups != -1) {
+	if (sudo_setgroups(ngroups, groups) != 0) {
+	    if (nonfatal)
+		goto done;
+	    sudo_fatal("setgroups");
+	}
+    }
+    if (euid != ROOT_UID) {
+	if (seteuid(euid) != 0) {
+	    if (nonfatal)
+		goto done;
+	    sudo_fatal("seteuid(%u)", (unsigned int)euid);
+	}
+    }
+    ret = 0;
+
+done:
+    errno = serrno;
+    debug_return_int(ret);
+}
+
+#if defined(HAVE_FACCESSAT) && defined(AT_EACCESS)
+static int
+switch_user_nonfatal(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups)
+{
+    return switch_user_int(euid, egid, ngroups, groups, true);
+}
+#endif
+
+void
+switch_user(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups)
+{
+    (void)switch_user_int(euid, egid, ngroups, groups, false);
+}
+
+static bool
+group_matches(gid_t target, const struct sudo_cred *cred)
+{
+    int i;
+    debug_decl(group_matches, SUDO_DEBUG_EDIT);
+
+    if (target == cred->gid) {
+	sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+	    "user gid %u matches directory gid %u", (unsigned int)cred->gid,
+	    (unsigned int)target);
+	debug_return_bool(true);
+    }
+    for (i = 0; i < cred->ngroups; i++) {
+	if (target == cred->groups[i]) {
+	    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+		"user gid %u matches directory gid %u",
+		(unsigned int)cred->groups[i], (unsigned int)target);
+	    debug_return_bool(true);
+	}
+    }
+    debug_return_bool(false);
+}
+
+static bool
+is_writable(const struct sudo_cred *user_cred, struct stat *sb)
+{
+    debug_decl(is_writable, SUDO_DEBUG_EDIT);
+
+    /* Other writable? */
+    if (ISSET(sb->st_mode, S_IWOTH)) {
+	sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+	    "directory is writable by other");
+	debug_return_int(true);
+    }
+
+    /* Group writable? */
+    if (ISSET(sb->st_mode, S_IWGRP)) {
+	if (group_matches(sb->st_gid, user_cred)) {
+	    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+		"directory is writable by one of the user's groups");
+	    debug_return_int(true);
+	}
+    }
+
+    errno = EACCES;
+    debug_return_int(false);
+}
+
+#if defined(HAVE_FACCESSAT) && defined(AT_EACCESS)
+/*
+ * Checks whether the open directory dfd is owned or writable by the user.
+ * Returns true if writable, false if not, or -1 on error.
+ */
+int
+dir_is_writable(int dfd, const struct sudo_cred *user_cred,
+    const struct sudo_cred *cur_cred)
+{
+    struct stat sb;
+    int rc;
+    debug_decl(dir_is_writable, SUDO_DEBUG_EDIT);
+
+    if (fstat(dfd, &sb) == -1)
+	debug_return_int(-1);
+
+    /* If the user owns the dir we always consider it writable. */
+    if (sb.st_uid == user_cred->uid) {
+	sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+	    "user uid %u matches directory uid %u",
+	    (unsigned int)user_cred->uid, (unsigned int)sb.st_uid);
+	debug_return_int(true);
+    }
+
+    /* Change uid/gid/groups to invoking user, usually needs root perms. */
+    if (cur_cred->euid != ROOT_UID) {
+	if (seteuid(ROOT_UID) != 0) {
+	    sudo_debug_printf(
+		SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+		"seteuid(ROOT_UID)");
+	    goto fallback;
+	}
+    }
+    if (switch_user_nonfatal(user_cred->uid, user_cred->gid, user_cred->ngroups,
+	    user_cred->groups) == -1) {
+	sudo_debug_printf(
+	    SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+	    "unable to switch to user_cred");
+	goto fallback;
+    }
+
+    /* Access checks are done using the euid/egid and group vector. */
+    rc = faccessat(dfd, ".", W_OK, AT_EACCESS);
+
+    /* Restore uid/gid/groups, may need root perms. */
+    if (user_cred->uid != ROOT_UID) {
+	if (seteuid(ROOT_UID) != 0)
+	    sudo_fatal("seteuid(ROOT_UID)");
+    }
+    switch_user(cur_cred->euid, cur_cred->egid, cur_cred->ngroups,
+	cur_cred->groups);
+
+    if (rc == 0)
+	debug_return_int(true);
+    if (errno == EACCES || errno == EPERM || errno == EROFS)
+	debug_return_int(false);
+    debug_return_int(-1);
+
+fallback:
+    debug_return_int(is_writable(user_cred, &sb));
+}
+#endif /* HAVE_FACCESSAT && AT_EACCESS */
+
+#if !defined(HAVE_FACCESSAT) || !defined(AT_EACCESS)
+/*
+ * Checks whether the open directory dfd is owned or writable by the user.
+ * Returns true if writable, false if not, or -1 on error.
+ */
+int
+dir_is_writable(int dfd, const struct sudo_cred *user_cred,
+    const struct sudo_cred *cur_cred)
+{
+    struct stat sb;
+    debug_decl(dir_is_writable, SUDO_DEBUG_EDIT);
+
+    if (fstat(dfd, &sb) == -1)
+	debug_return_int(-1);
+
+    /* If the user owns the dir we always consider it writable. */
+    if (sb.st_uid == user_cred->uid) {
+	sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+	    "user uid %u matches directory uid %u",
+	    (unsigned int)user_cred->uid, (unsigned int)sb.st_uid);
+	debug_return_int(true);
+    }
+
+    debug_return_int(is_writable(user_cred, &sb));
+}
+#endif /* HAVE_FACCESSAT && AT_EACCESS */
+
+#ifdef O_NOFOLLOW
+static int
+sudo_edit_openat_nofollow(int dfd, char *path, int oflags, mode_t mode)
+{
+    int fd;
+    debug_decl(sudo_edit_openat_nofollow, SUDO_DEBUG_EDIT);
+
+    fd = openat(dfd, path, oflags|O_NOFOLLOW, mode);
+    if (fd == -1) {
+	/* Handle non-standard O_NOFOLLOW errno values. */
+	if (errno == EMLINK)
+	    errno = ELOOP;		/* FreeBSD */
+#ifdef EFTYPE
+	else if (errno == EFTYPE)
+	    errno = ELOOP;		/* NetBSD */
+#endif
+    }
+
+    debug_return_int(fd);
+}
+#else
+/*
+ * Returns true if fd and path don't match or path is a symlink.
+ * Used on older systems without O_NOFOLLOW.
+ */
+static bool
+sudo_edit_is_symlink(int fd, char *path)
+{
+    struct stat sb1, sb2;
+    debug_decl(sudo_edit_is_symlink, SUDO_DEBUG_EDIT);
+
+    /*
+     * Treat [fl]stat() failure like there was a symlink.
+     */
+    if (fstat(fd, &sb1) == -1 || lstat(path, &sb2) == -1)
+	debug_return_bool(true);
+
+    /*
+     * Make sure we did not open a link and that what we opened
+     * matches what is currently on the file system.
+     */
+    if (S_ISLNK(sb2.st_mode) ||
+	sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino) {
+	debug_return_bool(true);
+    }
+
+    debug_return_bool(false);
+}
+
+static int
+sudo_edit_openat_nofollow(int dfd, char *path, int oflags, mode_t mode)
+{
+    int fd = -1, odfd = -1;
+    struct stat sb;
+    debug_decl(sudo_edit_openat_nofollow, SUDO_DEBUG_EDIT);
+
+    /* Save cwd and chdir to dfd */
+    if ((odfd = open(".", O_RDONLY)) == -1)
+	debug_return_int(-1);
+    if (fchdir(dfd) == -1) {
+	close(odfd);
+	debug_return_int(-1);
+    }
+
+    /*
+     * Check if path is a symlink.  This is racey but we detect whether
+     * we lost the race in sudo_edit_is_symlink() after the open.
+     */
+    if (lstat(path, &sb) == -1 && errno != ENOENT)
+	goto done;
+    if (S_ISLNK(sb.st_mode)) {
+	errno = ELOOP;
+	goto done;
+    }
+
+    fd = open(path, oflags, mode);
+    if (fd == -1)
+	goto done;
+
+    /*
+     * Post-open symlink check.  This will leave a zero-length file if
+     * O_CREAT was specified but it is too dangerous to try and remove it.
+     */
+    if (sudo_edit_is_symlink(fd, path)) {
+	close(fd);
+	fd = -1;
+	errno = ELOOP;
+    }
+
+done:
+    /* Restore cwd */
+    if (odfd != -1) {
+	if (fchdir(odfd) == -1)
+	    sudo_fatal("%s", U_("unable to restore current working directory"));
+	close(odfd);
+    }
+
+    debug_return_int(fd);
+}
+#endif /* O_NOFOLLOW */
+
+static int
+sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode,
+    const struct sudo_cred *user_cred, const struct sudo_cred *cur_cred)
+{
+    const int dflags = DIR_OPEN_FLAGS;
+    int dfd, fd, writable;
+    debug_decl(sudo_edit_open_nonwritable, SUDO_DEBUG_EDIT);
+
+    if (path[0] == '/') {
+	dfd = open("/", dflags);
+	path++;
+    } else {
+	dfd = open(".", dflags);
+	if (path[0] == '.' && path[1] == '/')
+	    path += 2;
+    }
+    if (dfd == -1)
+	debug_return_int(-1);
+
+    for (;;) {
+	char *slash;
+	int subdfd;
+
+	/*
+	 * Look up one component at a time, avoiding symbolic links in
+	 * writable directories.
+	 */
+	writable = dir_is_writable(dfd, user_cred, cur_cred);
+	if (writable == -1) {
+	    close(dfd);
+	    debug_return_int(-1);
+	}
+
+	path += strspn(path, "/");
+	slash = strchr(path, '/');
+	if (slash == NULL)
+	    break;
+	*slash = '\0';
+	if (writable)
+	    subdfd = sudo_edit_openat_nofollow(dfd, path, dflags, 0);
+	else
+	    subdfd = openat(dfd, path, dflags, 0);
+	*slash = '/';			/* restore path */
+	close(dfd);
+	if (subdfd == -1)
+	    debug_return_int(-1);
+	path = slash + 1;
+	dfd = subdfd;
+    }
+
+    if (writable) {
+	close(dfd);
+	errno = EISDIR;
+	debug_return_int(-1);
+    }
+
+    /*
+     * For "sudoedit /" we will receive ENOENT from openat() and sudoedit
+     * will try to create a file with an empty name.  We treat an empty
+     * path as the cwd so sudoedit can give a sensible error message.
+     */
+    fd = openat(dfd, *path ? path : ".", oflags, mode);
+    close(dfd);
+    debug_return_int(fd);
+}
+
+#ifdef O_NOFOLLOW
+int
+sudo_edit_open(char *path, int oflags, mode_t mode, unsigned int sflags,
+    const struct sudo_cred *user_cred, const struct sudo_cred *cur_cred)
+{
+    int fd;
+    debug_decl(sudo_edit_open, SUDO_DEBUG_EDIT);
+
+    if (!ISSET(sflags, CD_SUDOEDIT_FOLLOW))
+	oflags |= O_NOFOLLOW;
+    if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) {
+	fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode,
+	    user_cred, cur_cred);
+    } else {
+	fd = open(path, oflags|O_NONBLOCK, mode);
+    }
+    if (fd == -1 && ISSET(oflags, O_NOFOLLOW)) {
+	/* Handle non-standard O_NOFOLLOW errno values. */
+	if (errno == EMLINK)
+	    errno = ELOOP;		/* FreeBSD */
+#ifdef EFTYPE
+	else if (errno == EFTYPE)
+	    errno = ELOOP;		/* NetBSD */
+#endif
+    }
+    if (fd != -1 && !ISSET(oflags, O_NONBLOCK))
+	(void) fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
+    debug_return_int(fd);
+}
+#else
+int
+sudo_edit_open(char *path, int oflags, mode_t mode, unsigned int sflags,
+    const struct sudo_cred *user_cred, const struct sudo_cred *cur_cred)
+{
+    struct stat sb;
+    int fd;
+    debug_decl(sudo_edit_open, SUDO_DEBUG_EDIT);
+
+    /*
+     * Check if path is a symlink.  This is racey but we detect whether
+     * we lost the race in sudo_edit_is_symlink() after the file is opened.
+     */
+    if (!ISSET(sflags, CD_SUDOEDIT_FOLLOW)) {
+	if (lstat(path, &sb) == -1 && errno != ENOENT)
+	    debug_return_int(-1);
+	if (S_ISLNK(sb.st_mode)) {
+	    errno = ELOOP;
+	    debug_return_int(-1);
+	}
+    }
+
+    if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) {
+	fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode,
+	    user_cred, cur_cred);
+    } else {
+	fd = open(path, oflags|O_NONBLOCK, mode);
+    }
+    if (fd == -1)
+	debug_return_int(-1);
+    if (!ISSET(oflags, O_NONBLOCK))
+	(void) fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);
+
+    /*
+     * Post-open symlink check.  This will leave a zero-length file if
+     * O_CREAT was specified but it is too dangerous to try and remove it.
+     */
+    if (!ISSET(sflags, CD_SUDOEDIT_FOLLOW) && sudo_edit_is_symlink(fd, path)) {
+	close(fd);
+	fd = -1;
+	errno = ELOOP;
+    }
+
+    debug_return_int(fd);
+}
+#endif /* O_NOFOLLOW */
+
+/*
+ * Verify that the parent dir of a new file exists and is not writable
+ * by the user.  This fails early so the user knows ahead of time if the
+ * edit won't succeed.  Additional checks are performed when copying the
+ * temporary file back to the origin so there are no TOCTOU issues.
+ * Does not modify the value of errno.
+ */
+bool
+sudo_edit_parent_valid(char *path, unsigned int sflags,
+    const struct sudo_cred *user_cred, const struct sudo_cred *cur_cred)
+{
+    const int serrno = errno;
+    struct stat sb;
+    bool ret = false;
+    char *slash;
+    char pathbuf[2];
+    int dfd;
+    debug_decl(sudo_edit_parent_valid, SUDO_DEBUG_EDIT);
+
+    /* Get dirname of path (the slash is restored later). */
+    slash = strrchr(path, '/');
+    if (slash == NULL) {
+	/* cwd */
+	pathbuf[0] = '.';
+	pathbuf[1] = '\0';
+	path = pathbuf;
+    } else if (slash == path) {
+	pathbuf[0] = '/';
+	pathbuf[1] = '\0';
+	path = pathbuf;
+	slash = NULL;
+    } else {
+	*slash = '\0';
+    }
+
+    /*
+     * The parent directory is allowed to be a symbolic link unless
+     * *its* parent is writable and CD_SUDOEDIT_CHECK is set.
+     */
+    dfd = sudo_edit_open(path, DIR_OPEN_FLAGS, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH,
+	sflags|CD_SUDOEDIT_FOLLOW, user_cred, cur_cred);
+    if (dfd != -1) {
+	if (fstat(dfd, &sb) == 0 && S_ISDIR(sb.st_mode))
+	    ret = true;
+	close(dfd);
+    }
+    if (slash != NULL)
+	*slash = '/';
+
+    /* Restore errno. */
+    errno = serrno;
+
+    debug_return_bool(ret);
+}
+
+#endif /* HAVE_SETRESUID || HAVE_SETREUID || HAVE_SETEUID */