WIP dir support (also demons)

Signed-off-by: Leah Rowe <leah@libreboot.org>

2 files changed, 294 insertions, 81 deletions

diff --git a/util/nvmutil/include/common.h b/util/nvmutil/include/common.h
index 0fedeedd..67969832 100644
--- a/util/nvmutil/include/common.h
+++ b/util/nvmutil/include/common.h
@@ -36,6 +36,13 @@
 
 int fchmod(int fd, mode_t mode);
 
+#define MKHTEMP_RETRY_MAX 512
+#define MKHTEMP_SPIN_THRESHOLD 32
+
+#define MKHTEMP_FILE 0
+#define MKHTEMP_DIR  1
+
+
 /* if 1: on operations that
  * check ownership, always
  * permit root to access even
@@ -493,10 +500,11 @@ static int mkhtemp_try_create(int dirfd,
     char *p,
     size_t xc,
     int *fd,
-    struct stat *st);
+    struct stat *st,
+    int type);
 int mkhtemp(int *fd, struct stat *st,
     char *template, int dirfd, const char *fname,
-    struct stat *st_dir_initial);
+    struct stat *st_dir_initial, int type);
 int mkhtemp_fill_random(char *p, size_t xc);
 int world_writeable_and_sticky(const char *s,
     int sticky_allowed, int always_sticky);
@@ -529,6 +537,8 @@ int fs_dirname_basename(const char *path,
     char **dir, char **base, int allow_relative);
 int openat2p(int dirfd, const char *path,
     int flags, mode_t mode);
+int mkdirat_on_eintr(int dirfd, 
+    const char *pathname, mode_t mode);
 
 /* asserts */
 
diff --git a/util/nvmutil/lib/file.c b/util/nvmutil/lib/file.c
index f0cb5ad4..a490b358 100644
--- a/util/nvmutil/lib/file.c
+++ b/util/nvmutil/lib/file.c
@@ -30,9 +30,6 @@
 /* check that a file changed
  */
 
-#define MKHTEMP_RETRY_MAX 512
-#define MKHTEMP_SPIN_THRESHOLD 32
-
 int
 same_file(int fd, struct stat *st_old,
     int check_size)
@@ -109,7 +106,7 @@ xopen(int *fd_ptr, const char *path, int flags, struct stat *st)
 	if (!S_ISREG(st->st_mode))
 		err(errno, "%s: not a regular file", path);
 
-	if (lseek(*fd_ptr, 0, SEEK_CUR) == (off_t)-1)
+	if (lseek_on_eintr(*fd_ptr, 0, SEEK_CUR, 1, 1) == (off_t)-1)
 		err(errno, "%s: file not seekable", path);
 }
 
@@ -131,6 +128,8 @@ fsync_dir(const char *path)
 	char *slash = NULL;
 	struct stat st = {0};
 
+	int close_errno;
+
 #if defined(PATH_LEN) && \
     (PATH_LEN) >= 256
 	maxlen = PATH_LEN;
@@ -233,7 +232,9 @@ err_fsync_dir:
 
 	if (dirfd >= 0) {
 
+		close_errno = errno;
 		(void) close_on_eintr(dirfd);
+		errno = close_errno;
 		dirfd = -1;
 	}
 
@@ -263,6 +264,7 @@ new_tmpfile(int *fd, char **path)
 	    "tmpXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
 	char *tmpdir = NULL;
 
+	int close_errno;
 	size_t dirlen;
 	size_t destlen;
 	char *dest = NULL; /* final path */
@@ -275,15 +277,26 @@ new_tmpfile(int *fd, char **path)
 	if (path == NULL || fd == NULL) {
 		errno = EFAULT;
 		goto err_new_tmpfile;
-	} else if (*path == NULL) {
-		errno = EFAULT;
-		goto err_new_tmpfile;
 	}
 
-	if (*fd >= 0) { /* file already opend */
+	/* don't mess with someone's file
+	 * if already opened
+	 */
+	if (*fd >= 0) {
 		errno = EEXIST;
 		goto err_new_tmpfile;
 	}
+
+	/* regarding **path:
+	 * the pointer (to the pointer)
+	 * must nott be null, but we don't
+	 * care about the pointer it points
+	 * to. you should expect it to be
+	 * replaced upon successful return
+	 *
+	 * (on error, it will not be touched)
+	 */
+
 	*fd = -1;
 
 #if defined(PERMIT_NON_STICKY_ALWAYS) && \
@@ -335,12 +348,15 @@ new_tmpfile(int *fd, char **path)
 	if (fstat(dirfd, &st_dir_initial) < 0)
 		goto err_new_tmpfile;
 
-	*fd = mkhtemp(fd, &st, dest, dirfd, fname, &st_dir_initial);
+	*fd = mkhtemp(fd, &st, dest, dirfd,
+	    fname, &st_dir_initial, MKHTEMP_FILE);
 	if (*fd < 0)
 		goto err_new_tmpfile;
 
 	if (dirfd >= 0) {
+		close_errno = errno;
 		(void) close_on_eintr(dirfd);
+		errno = close_errno;
 		dirfd = -1;
 	}
 
@@ -363,14 +379,16 @@ err_new_tmpfile:
 	}
 
 	if (dirfd >= 0) {
-
+		close_errno = errno;
 		(void) close_on_eintr(dirfd);
+		errno = close_errno;
 		dirfd = -1;
 	}
 
 	if (*fd >= 0) {
-
+		close_errno = errno;
 		(void) close_on_eintr(*fd);
+		errno = close_errno;
 		*fd = -1;
 	}
 
@@ -661,18 +679,53 @@ sticky_hell:
 
 /* mk(h)temp - hardened mktemp.
  * like mkstemp, but (MUCH) harder.
- * TODO:
- * directory support (currently only
- *                    generates files)
+ *
+ * designed to resist TOCTOU attacsk
+ * e.g. directory race / symlink attack
+ * 
+ * extremely strict and even implements
+ * some limited userspace-level sandboxing,
+ * similar to openbsd unveil (which you
+ * can also use with this in your program)
+ *
+ * supports both files and directories.
+ * file: type = MKHTEMP_FILE (0)
+ * dir: type = MKHTEMP_DIR (1)
+ *
+ * DESIGN NOTES:
+ *
+ * caller is expected to handle
+ * cleanup e.g. free(), on *st,
+ * *template, *fname (all of the
+ * pointers). ditto fd cleanup.
+ *
+ * some limited cleanup is
+ * performed here, e.g. directory/file
+ * cleanup on error in mkhtemp_try_create
+ *
+ * we only check if these are not NULL,
+ * and the caller is expected to take
+ * care; without too many conditions,
+ * these functions are more flexible,
+ * but some precauttions are taken:
+ *
+ * when used via the function new_tmpfile
+ * or new_tmpdir, thtis is extremely strict,
+ * much stricter than previous mktemp
+ * variants. for example, it is much
+ * stricter about stickiness on world
+ * writeable directories, and it enforces
+ * file ownership under hardened mode
+ * (only lets you touch your own files/dirs)
  */
-
 int
 mkhtemp(int *fd,
     struct stat *st,
     char *template,
     int dirfd,
     const char *fname,
-    struct stat *st_dir_initial)
+    struct stat *st_dir_initial,
+    int type)
 {
 	size_t len = 0;
 	size_t xc = 0;
@@ -683,6 +736,7 @@ mkhtemp(int *fd,
 
 	size_t retries;
 
+	int close_errno;
 	int saved_errno = errno;
 
 #if defined(PATH_LEN) && \
@@ -703,8 +757,11 @@ mkhtemp(int *fd,
 		return -1;
 	}
 
+	/* we do not mess with an
+	   open descriptor.
+	 */
 	if (*fd >= 0) {
-		errno = EEXIST;
+		errno = EEXIST; /* leave their file alone */
 		return -1;
 	}
 
@@ -778,13 +835,20 @@ mkhtemp(int *fd,
 		    p,
 		    xc,
 		    fd,
-		    st);
+		    st,
+		    type);
 
-		if (r != 1) {
-			if (retries >= MKHTEMP_SPIN_THRESHOLD)
+		if (r == 0) {
+			if (retries >= MKHTEMP_SPIN_THRESHOLD) {
+				/* usleep can return EINTR */
+				close_errno = errno;
 				usleep((useconds_t)rlong() & 0x3FF);
+				errno = close_errno;
+			}
 			continue;
 		}
+		if (r < 0)
+			goto err;
 
 		/* success: copy final name back */
 		memcpy(template + len - fname_len,
@@ -798,7 +862,9 @@ mkhtemp(int *fd,
 
 err:
 	if (*fd >= 0) {
+		close_errno = errno;
 		(void)close_on_eintr(*fd);
+		errno = close_errno;
 		*fd = -1;
 	}
 
@@ -817,34 +883,75 @@ mkhtemp_try_create(int dirfd,
     char *p,
     size_t xc,
     int *fd,
-    struct stat *st)
+    struct stat *st,
+    int type)
 {
-	struct stat st_dir_now;
 	struct stat st_open;
 	int saved_errno = errno;
 	int close_errno;
 	int rval = -1;
 
-	if (mkhtemp_fill_random(p, xc) < 0)
+	int file_created = 0;
+	int dir_created = 0;
+
+	if (fd == NULL || st == NULL || p == NULL || fname_copy == NULL ||
+	    st_dir_initial == NULL) {
+		errno = EFAULT;
+		goto err;
+	} else if (*fd >= 0) { /* do not mess with someone else's file */
+		errno = EEXIST;
 		goto err;
+	}
 
-	if (fstat(dirfd, &st_dir_now) < 0)
+	if (mkhtemp_fill_random(p, xc) < 0)
 		goto err;
 
 	if (fd_verify_dir_identity(dirfd, st_dir_initial) < 0)
 		goto err;
 
-	*fd = openat2p(dirfd, fname_copy,
-	    O_RDWR | O_CREAT | O_EXCL |
-	    O_NOFOLLOW | O_CLOEXEC | O_NOCTTY,
-	    0600);
+	if (type == MKHTEMP_FILE) {
+		*fd = openat2p(dirfd, fname_copy,
+		    O_RDWR | O_CREAT | O_EXCL |
+		    O_NOFOLLOW | O_CLOEXEC | O_NOCTTY,
+		    0600);
+
+		/* O_CREAT and O_EXCL guarantees
+		 * creation upon success
+		 */
+		if (*fd >= 0)
+			file_created = 1;
+
+	} else { /* dir: MKHTEMP_DIR */
+
+		if (mkdirat_on_eintr(dirfd, fname_copy, 0700) < 0)
+			goto err;
+
+		/* ^ NOTE: opening the directory here
+		           will never set errno=EEXIST,
+		  	   since we're not creating it */
+
+		dir_created = 1;
+
+		/* do it again (mitigate directory race) */
+		if (fd_verify_dir_identity(dirfd, st_dir_initial) < 0)
+			goto err;
+
+		*fd = openat2p(dirfd, fname_copy,
+		    O_RDONLY | O_DIRECTORY | O_CLOEXEC, 0);
+		if (*fd < 0)
+			goto err;
+
+		if (fd_verify_dir_identity(dirfd, st_dir_initial) < 0)
+			goto err;
+
+	}
+
+	/* NOTE: openat2p and mkdirat_on_eintr
+	 * already handled EINTR/EAGAIN looping
+	 */
 
 	if (*fd < 0) {
-		if (errno == EEXIST ||
-		    errno == EINTR ||
-		    errno == EAGAIN ||
-		    errno == EWOULDBLOCK ||
-		    errno == ETXTBSY) {
+		if (errno == EEXIST) {
 
 			rval = 0;
 			goto out;
@@ -852,17 +959,37 @@ mkhtemp_try_create(int dirfd,
 		goto err;
 	}
 
-	/* fd is now live */
-
 	if (fstat(*fd, &st_open) < 0)
 		goto err;
 
-	if (fd_verify_dir_identity(dirfd, st_dir_initial) < 0)
-		goto err;
+	if (type == MKHTEMP_FILE) {
 
-	if (secure_file(fd, st, &st_open,
-	    O_APPEND, 1, 1, 0600) < 0)
-		goto err;
+		if (fd_verify_dir_identity(dirfd, st_dir_initial) < 0)
+			goto err;
+
+		if (secure_file(fd, st, &st_open,
+		    O_APPEND, 1, 1, 0600) < 0) /* WARNING: only once */
+			goto err;
+
+	} else { /* dir: MKHTEMP_DIR */
+
+		if (fd_verify_identity(*fd, &st_open, st_dir_initial) < 0)
+			goto err;
+
+		if (!S_ISDIR(st_open.st_mode)) {
+			errno = ENOTDIR;
+			goto err;
+		}
+
+		if (is_owner(&st_open) < 0)
+			goto err;
+
+		/* group/world writeable */
+		if (st_open.st_mode & (S_IWGRP | S_IWOTH)) {
+			errno = EPERM;
+			goto err;
+		}
+	}
 
 	errno = saved_errno;
 	rval = 1;
@@ -876,6 +1003,12 @@ err:
 		*fd = -1;
 	}
 
+	if (file_created)
+		(void) unlinkat(dirfd, fname_copy, 0);
+
+	if (dir_created)
+		(void) unlinkat(dirfd, fname_copy, AT_REMOVEDIR);
+
 	errno = close_errno;
 	rval = -1;
 out:
@@ -947,6 +1080,11 @@ err_mkhtemp_fill_random:
 	return -1;
 }
 
+/* WARNING: **ONCE** per file.
+ *
+ *	!!! DO NOT RUN TWICE PER FILE. BEWARE OF THE DEMON !!!
+ *	               watch out for spikes!
+ */
 int secure_file(int *fd,
     struct stat *st,
     struct stat *expected,
@@ -958,25 +1096,25 @@ int secure_file(int *fd,
 	int flags;
 	struct stat st_now;
 	int saved_errno = errno;
-
+	/* you have been warned */
 	if (fd == NULL) {
 		errno = EFAULT;
-		goto err_secure_file;
+		goto err_demons;
 	}
 	if (*fd < 0) {
 		errno = EBADF;
-		goto err_secure_file;
+		goto err_demons;
 	}
 
 	if (st == NULL) {
 		errno = EFAULT;
-		goto err_secure_file;
+		goto err_demons;
 	}
 
 	flags = fcntl(*fd, F_GETFL);
 
 	if (flags == -1)
-		goto err_secure_file;
+		goto err_demons;
 
 	if (bad_flags > 0) {
 
@@ -984,49 +1122,49 @@ int secure_file(int *fd,
 		 * by allowing offsets to be ignored */
 		if (flags & bad_flags) {
 			errno = EPERM;
-			goto err_secure_file;
+			goto err_demons;
 		}
 	}
 
-	if (fstat(*fd, &st_now) == -1)
-		goto err_secure_file;
-
 	if (expected != NULL) {
-		if (fd_verify_identity(*fd, expected, &st_now) < 0)
-			goto err_secure_file;
-	}
+		if (fd_verify_regular(*fd, expected, st) < 0)
+			goto err_demons;
+	} else {
+		if (fstat(*fd, &st_now) == -1)
+			goto err_demons;
 
-	*st = st_now;
+		if (!S_ISREG(st_now.st_mode)) {
+			errno = EBADF;
+			goto err_demons;
+		}
 
-	if (!S_ISREG(st->st_mode)) {
-		errno = EBADF;
-		goto err_secure_file;
+		*st = st_now;
 	}
 
-	if (fd_verify_regular(*fd, expected, st) < 0)
-		goto err_secure_file;
-
 	if (check_seek) {
 
 		/* check if it's seekable */
 		if (lseek(*fd, 0, SEEK_CUR) == (off_t)-1)
-			goto err_secure_file;
+			goto err_demons;
 	}
 
-	/* tmpfile re/un linked while open */
-	if (st->st_nlink != 1) {
-		errno = ELOOP;
-		goto err_secure_file;
+	/* don't release the demon
+	 */
+	if (st->st_nlink != 1) { /***********/
+		                 /* ( >:3 ) */
+		errno = ELOOP;   /*  /| |\  */  /* don't let him out */
+		goto err_demons; /*   / \   */
+	                         /***********/
 	}
 
 	if (st->st_uid != geteuid() && /* someone else's file */
 	    geteuid() != 0) { /* override for root */
 
 		errno = EPERM;
-		goto err_secure_file;
+		goto err_demons;
 	}
 	if (is_owner(st) < 0)
-		goto err_secure_file;
+		goto err_demons;
 
 	/* world-writeable or group-ownership.
 	 * if these are set, then others could
@@ -1034,26 +1172,26 @@ int secure_file(int *fd,
 	 */
 	if (st->st_mode & (S_IWGRP | S_IWOTH)) {
 		errno = EPERM;
-		goto err_secure_file;
+		goto err_demons;
 	}
 
 	if (do_lock) {
 		if (lock_file(*fd, flags) == -1)
-			goto err_secure_file;
+			goto err_demons;
 
 		if (expected != NULL) {
 			if (fd_verify_identity(*fd, expected, &st_now) < 0)
-				goto err_secure_file;
+				goto err_demons;
 		}
 	}
 
 	if (fchmod(*fd, mode) == -1)
-		goto err_secure_file;
+		goto err_demons;
 
 	errno = saved_errno;
 	return 0;
 
-err_secure_file:
+err_demons:
 
 	if (errno == saved_errno)
 		errno = EIO;
@@ -1674,7 +1812,9 @@ lseek_on_eintr(int fd, off_t off, int whence,
 		old = lseek(fd, off, whence);
 	} while (old == (off_t)-1 && (
 	    errno == try_err(loop_eintr, EINTR) ||
-	    errno == try_err(loop_eagain, EAGAIN)));
+	    errno == try_err(loop_eintr, ETXTBSY) ||
+	    errno == try_err(loop_eagain, EAGAIN) ||
+	    errno == try_err(loop_eagain, EWOULDBLOCK)));
 
 	return old;
 }
@@ -1697,7 +1837,9 @@ close_on_eintr(int fd)
 
 	do {
 		r = close(fd);
-	} while (r == -1 && (errno == EINTR || errno == EAGAIN));
+	} while (r == -1 && (
+	    errno == EINTR || errno == EAGAIN ||
+	    errno == EWOULDBLOCK || errno == ETXTBSY));
 
 	if (r >= 0)
 		errno = saved_errno;
@@ -1713,7 +1855,8 @@ fsync_on_eintr(int fd)
 
 	do {
 		r = fsync(fd);
-	} while (r == -1 && (errno == EINTR || errno == EAGAIN));
+	} while (r == -1 && (errno == EINTR || errno == EAGAIN ||
+	    errno == ETXTBSY || errno == EWOULDBLOCK));
 
 	if (r >= 0)
 		errno = saved_errno;
@@ -1797,6 +1940,8 @@ fs_mkdir_p_at(int dirfd, const char *path, mode_t mode)
 	struct stat st_parent_initial;
 	struct stat st_parent_now;
 	int saved_errno = errno;
+	int close_errno;
+	int dir_created = 0;
 	int r;
 
 	if (path == NULL) {
@@ -1834,16 +1979,20 @@ fs_mkdir_p_at(int dirfd, const char *path, mode_t mode)
 			if (errno != ENOENT)
 				goto err;
 
-			if (mkdirat(dirfd, name, mode) < 0)
+			if (mkdirat_on_eintr(dirfd, name, mode) < 0)
 				goto err;
 
+			dir_created = 1;
+
 			nextfd = openat2p(dirfd, name,
 			    O_RDONLY | O_DIRECTORY | O_CLOEXEC, 0);
 			if (nextfd < 0)
 				goto err;
 		}
 
+		close_errno = errno;
 		(void)close_on_eintr(dirfd);
+		errno = close_errno;
 		dirfd = nextfd;
 		nextfd = -1;
 
@@ -1855,9 +2004,11 @@ fs_mkdir_p_at(int dirfd, const char *path, mode_t mode)
 
 err:
 	if (dirfd >= 0)
-		(void)close_on_eintr(dirfd);
+		(void) close_on_eintr(dirfd);
 	if (nextfd >= 0)
-		(void)close_on_eintr(nextfd);
+		(void) close_on_eintr(nextfd);
+	if (dir_created)
+		(void) unlinkat(dirfd, name, AT_REMOVEDIR);
 
 	errno = saved_errno;
 	return (-1);
@@ -2122,6 +2273,7 @@ fs_dirname_basename(const char *path,
  * with fallback for others e.g. openbsd
  *
  * BONUS: arg checks
+ * TODO: consider EINTR/EAGAIN retry loop
  */
 int
 openat2p(int dirfd, const char *path,
@@ -2137,6 +2289,8 @@ openat2p(int dirfd, const char *path,
 		    RESOLVE_NO_MAGICLINKS |
 		    RESOLVE_NO_XDEV
 	};
+	int saved_errno = errno;
+	int rval;
 #endif
 
 	if (dirfd < 0) {
@@ -2149,15 +2303,64 @@ openat2p(int dirfd, const char *path,
 		return -1;
 	}
 
+retry:
+	errno = 0;
+
 #ifdef __linux__
 	/* more secure than regular openat,
 	 * but linux-only at the time of writing
 	 */
-	return syscall(SYS_openat2, dirfd, path, &how, sizeof(how));
+	rval = syscall(SYS_openat2, dirfd, path, &how, sizeof(how));
 #else
 	/* less secure, but e.g. openbsd
 	 * doesn't have openat2 yet
 	 */
-	return openat(dirfd, path, flags, mode);
+	rval = openat(dirfd, path, flags, mode);
 #endif
+	if (rval == -1 && (
+	    errno == EINTR ||
+	    errno == EAGAIN ||
+	    errno == EWOULDBLOCK ||
+	    errno == ETXTBSY))
+		goto retry;
+
+	if (rval >= 0)
+		errno = saved_errno;
+
+	return rval;
+}
+
+int
+mkdirat_on_eintr( /* <-- say that 10 times to please the demon */
+    int dirfd, 
+    const char *path, mode_t mode)
+{
+	int saved_errno = errno;
+	int rval;
+
+	if (dirfd < 0) {
+		errno = EBADF;
+		return -1;
+	}
+
+	if (path == NULL) {
+		errno = EFAULT;
+		return -1;
+	}
+
+retry:
+	errno = 0;
+	rval = mkdirat(dirfd, path, mode);
+
+	if (rval == -1 && (
+	    errno == EINTR ||
+	    errno == EAGAIN ||
+	    errno == EWOULDBLOCK ||
+	    errno == ETXTBSY))
+		goto retry;
+
+	if (rval >= 0)
+		errno = saved_errno;
+
+	return rval;
 }