sudo: add upstream security patch for CVE-2017-1000367

CVE-2017-1000367 - Potential overwrite of arbitrary files on Linux

On Linux systems, sudo parses the /proc/[pid]/stat file to determine the
device number of the process's tty (field 7).  The fields in the file are
space-delimited, but it is possible for the command name (field 2) to
include spaces, which sudo does not account for.  A user with sudo
privileges can cause sudo to use a device number of the user's choosing by
creating a symbolic link from the sudo binary to a name that contains a
space, followed by a number.

If SELinux is enabled on the system and sudo was built with SELinux support,
a user with sudo privileges may be able to to overwrite an arbitrary file.
This can be escalated to full root access by rewriting a trusted file such
as /etc/shadow or even /etc/sudoers.

For more details, see: https://www.sudo.ws/alerts/linux_tty.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/sudo/0001-fix-CVE-2017-1000367.patch

@@ -0,0 +1,264 @@
+Downloaded from upstream: https://www.sudo.ws/repos/sudo/raw-rev/b5460cbbb11b
+
+# HG changeset patch
+# User Todd C. Miller <Todd.Miller@courtesan.com>
+# Date 1496089973 21600
+# Node ID b5460cbbb11bbf9d92ffcc6798a686cf4125efd3
+# Parent  c303e6eecc7841e2f891d70613e80fcf27fa6e86
+Fix for CVE-2017-1000367, parsing of /proc/pid/stat on Linux when
+the process name contains spaces.  Since the user has control over
+the command name this could be used by a user with sudo access to
+overwrite an arbitrary file.
+Thanks to Qualys for investigating and reporting this bug.
+
+Also stop performing a breadth-first traversal of /dev when looking
+for the device.  Only the directories specified in search_devs[]
+are checked.
+
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+diff -r c303e6eecc78 -r b5460cbbb11b src/ttyname.c
+--- a/src/ttyname.c	Tue May 23 13:26:54 2017 -0600
++++ b/src/ttyname.c	Mon May 29 14:32:53 2017 -0600
+@@ -1,5 +1,5 @@
+ /*
+- * Copyright (c) 2012-2016 Todd C. Miller <Todd.Miller@courtesan.com>
++ * Copyright (c) 2012-2017 Todd C. Miller <Todd.Miller@courtesan.com>
+  *
+  * Permission to use, copy, modify, and distribute this software for any
+  * purpose with or without fee is hereby granted, provided that the above
+@@ -145,20 +145,22 @@
+ }
+ #elif defined(HAVE_STRUCT_PSINFO_PR_TTYDEV) || defined(HAVE_PSTAT_GETPROC) || defined(__linux__)
+ /*
+- * Devices to search before doing a breadth-first scan.
++ * Device nodes and directories to search before searching all of /dev
+  */
+ static char *search_devs[] = {
+     "/dev/console",
+-    "/dev/wscons",
+-    "/dev/pts/",
+-    "/dev/vt/",
+-    "/dev/term/",
+-    "/dev/zcons/",
++    "/dev/pts/",	/* POSIX pty */
++    "/dev/vt/",		/* Solaris virtual console */
++    "/dev/term/",	/* Solaris serial ports */
++    "/dev/zcons/",	/* Solaris zone console */
++    "/dev/pty/",	/* HP-UX old-style pty */
+     NULL
+ };
+ 
++/*
++ * Device nodes to ignore when searching all of /dev
++ */
+ static char *ignore_devs[] = {
+-    "/dev/fd/",
+     "/dev/stdin",
+     "/dev/stdout",
+     "/dev/stderr",
+@@ -166,16 +168,18 @@
+ };
+ 
+ /*
+- * Do a breadth-first scan of dir looking for the specified device.
++ * Do a scan of a directory looking for the specified device.
++ * Does not descend into subdirectories.
+  * Returns name on success and NULL on failure, setting errno.
+  */
+ static char *
+-sudo_ttyname_scan(const char *dir, dev_t rdev, bool builtin, char *name, size_t namelen)
++sudo_ttyname_scan(const char *dir, dev_t rdev, char *name, size_t namelen)
+ {
+-    size_t sdlen, num_subdirs = 0, max_subdirs = 0;
+-    char pathbuf[PATH_MAX], **subdirs = NULL;
++    size_t sdlen;
++    char pathbuf[PATH_MAX];
+     char *ret = NULL;
+     struct dirent *dp;
++    struct stat sb;
+     unsigned int i;
+     DIR *d = NULL;
+     debug_decl(sudo_ttyname_scan, SUDO_DEBUG_UTIL)
+@@ -187,6 +191,18 @@
+     if ((d = opendir(dir)) == NULL)
+ 	goto done;
+ 
++    if (fstat(dirfd(d), &sb) == -1) {
++	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
++	    "unable to fstat %s", dir);
++	goto done;
++    }
++    if ((sb.st_mode & S_IWOTH) != 0) {
++	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
++	    "ignoring world-writable directory %s", dir);
++	errno = ENOENT;
++	goto done;
++    }
++
+     sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+ 	"scanning for dev %u in %s", (unsigned int)rdev, dir);
+ 
+@@ -224,18 +240,6 @@
+ 	}
+ 	if (ignore_devs[i] != NULL)
+ 	    continue;
+-	if (!builtin) {
+-	    /* Skip entries in search_devs; we already checked them. */
+-	    for (i = 0; search_devs[i] != NULL; i++) {
+-		len = strlen(search_devs[i]);
+-		if (search_devs[i][len - 1] == '/')
+-		    len--;
+-		if (d_len == len && strncmp(pathbuf, search_devs[i], len) == 0)
+-		    break;
+-	    }
+-	    if (search_devs[i] != NULL)
+-		continue;
+-	}
+ # if defined(HAVE_STRUCT_DIRENT_D_TYPE) && defined(DTTOIF)
+ 	/*
+ 	 * Avoid excessive stat() calls by checking dp->d_type.
+@@ -248,39 +252,14 @@
+ 		if (stat(pathbuf, &sb) == -1)
+ 		    continue;
+ 		break;
+-	    case DT_DIR:
+-		/* Directory, no need to stat() it. */
+-		sb.st_mode = DTTOIF(dp->d_type);
+-		sb.st_rdev = 0;		/* quiet ccc-analyzer false positive */
+-		break;
+ 	    default:
+-		/* Not a character device, link or directory, skip it. */
++		/* Not a character device or link, skip it. */
+ 		continue;
+ 	}
+ # else
+ 	if (stat(pathbuf, &sb) == -1)
+ 	    continue;
+ # endif
+-	if (S_ISDIR(sb.st_mode)) {
+-	    if (!builtin) {
+-		/* Add to list of subdirs to search. */
+-		if (num_subdirs + 1 > max_subdirs) {
+-		    char **new_subdirs;
+-
+-		    new_subdirs = reallocarray(subdirs, max_subdirs + 64,
+-			sizeof(char *));
+-		    if (new_subdirs == NULL)
+-			goto done;
+-		    subdirs = new_subdirs;
+-		    max_subdirs += 64;
+-		}
+-		subdirs[num_subdirs] = strdup(pathbuf);
+-		if (subdirs[num_subdirs] == NULL)
+-		    goto done;
+-		num_subdirs++;
+-	    }
+-	    continue;
+-	}
+ 	if (S_ISCHR(sb.st_mode) && sb.st_rdev == rdev) {
+ 	    sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
+ 		"resolved dev %u as %s", (unsigned int)rdev, pathbuf);
+@@ -296,16 +275,9 @@
+ 	}
+     }
+ 
+-    /* Search subdirs if we didn't find it in the root level. */
+-    for (i = 0; ret == NULL && i < num_subdirs; i++)
+-	ret = sudo_ttyname_scan(subdirs[i], rdev, false, name, namelen);
+-
+ done:
+     if (d != NULL)
+ 	closedir(d);
+-    for (i = 0; i < num_subdirs; i++)
+-	free(subdirs[i]);
+-    free(subdirs);
+     debug_return_str(ret);
+ }
+ 
+@@ -324,7 +296,7 @@
+     debug_decl(sudo_ttyname_dev, SUDO_DEBUG_UTIL)
+ 
+     /*
+-     * First check search_devs for common tty devices.
++     * First check search_devs[] for common tty devices.
+      */
+     for (sd = search_devs; (devname = *sd) != NULL; sd++) {
+ 	len = strlen(devname);
+@@ -349,7 +321,7 @@
+ 		    "comparing dev %u to %s: no", (unsigned int)rdev, buf);
+ 	    } else {
+ 		/* Traverse directory */
+-		ret = sudo_ttyname_scan(devname, rdev, true, name, namelen);
++		ret = sudo_ttyname_scan(devname, rdev, name, namelen);
+ 		if (ret != NULL || errno == ENOMEM)
+ 		    goto done;
+ 	    }
+@@ -367,9 +339,9 @@
+     }
+ 
+     /*
+-     * Not found?  Do a breadth-first traversal of /dev/.
++     * Not found?  Check all device nodes in /dev.
+      */
+-    ret = sudo_ttyname_scan(_PATH_DEV, rdev, false, name, namelen);
++    ret = sudo_ttyname_scan(_PATH_DEV, rdev, name, namelen);
+ 
+ done:
+     debug_return_str(ret);
+@@ -493,28 +465,35 @@
+ 	len = getline(&line, &linesize, fp);
+ 	fclose(fp);
+ 	if (len != -1) {
+-	    /* Field 7 is the tty dev (0 if no tty) */
+-	    char *cp = line;
+-	    char *ep = line;
+-	    const char *errstr;
+-	    int field = 0;
+-	    while (*++ep != '\0') {
+-		if (*ep == ' ') {
+-		    *ep = '\0';
+-		    if (++field == 7) {
+-			dev_t tdev = strtonum(cp, INT_MIN, INT_MAX, &errstr);
+-			if (errstr) {
+-			    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+-				"%s: tty device %s: %s", path, cp, errstr);
++	    /*
++	     * Field 7 is the tty dev (0 if no tty).
++	     * Since the process name at field 2 "(comm)" may include spaces,
++	     * start at the last ')' found.
++	     */
++	    char *cp = strrchr(line, ')');
++	    if (cp != NULL) {
++		char *ep = cp;
++		const char *errstr;
++		int field = 1;
++
++		while (*++ep != '\0') {
++		    if (*ep == ' ') {
++			*ep = '\0';
++			if (++field == 7) {
++			    dev_t tdev = strtonum(cp, INT_MIN, INT_MAX, &errstr);
++			    if (errstr) {
++				sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
++				    "%s: tty device %s: %s", path, cp, errstr);
++			    }
++			    if (tdev > 0) {
++				errno = serrno;
++				ret = sudo_ttyname_dev(tdev, name, namelen);
++				goto done;
++			    }
++			    break;
+ 			}
+-			if (tdev > 0) {
+-			    errno = serrno;
+-			    ret = sudo_ttyname_dev(tdev, name, namelen);
+-			    goto done;
+-			}
+-			break;
++			cp = ep + 1;
+ 		    }
+-		    cp = ep + 1;
+ 		}
+ 	    }
+ 	}
+