upstream: add a local implementation of BSD realpath() for

sftp-server use ahead of OpenBSD's realpath changing to match POSIX;

ok deraadt@ (thanks for snaps testing)

OpenBSD-Commit-ID: 4f8cbf7ed8679f6237264301d104ecec64885d55

1 files changed, 224 insertions, 0 deletions

diff --git a/sftp-realpath.c b/sftp-realpath.c
new file mode 100644
index 000000000..0ed808f46
--- /dev/null
+++ b/sftp-realpath.c
@@ -0,0 +1,224 @@
+/*	$OpenBSD: sftp-realpath.c,v 1.1 2019/07/05 04:55:40 djm Exp $ */
+/*
+ * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The names of the authors may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+
+#ifndef SYMLOOP_MAX
+# define SYMLOOP_MAX 32
+#endif
+
+/* XXX rewrite sftp-server to use POSIX realpath and remove this hack */
+
+char *sftp_realpath(const char *path, char *resolved);
+
+/*
+ * char *realpath(const char *path, char resolved[PATH_MAX]);
+ *
+ * Find the real name of path, by removing all ".", ".." and symlink
+ * components.  Returns (resolved) on success, or (NULL) on failure,
+ * in which case the path which caused trouble is left in (resolved).
+ */
+char *
+sftp_realpath(const char *path, char *resolved)
+{
+	struct stat sb;
+	char *p, *q, *s;
+	size_t left_len, resolved_len;
+	unsigned symlinks;
+	int serrno, slen, mem_allocated;
+	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
+
+	if (path[0] == '\0') {
+		errno = ENOENT;
+		return (NULL);
+	}
+
+	serrno = errno;
+
+	if (resolved == NULL) {
+		resolved = malloc(PATH_MAX);
+		if (resolved == NULL)
+			return (NULL);
+		mem_allocated = 1;
+	} else
+		mem_allocated = 0;
+
+	symlinks = 0;
+	if (path[0] == '/') {
+		resolved[0] = '/';
+		resolved[1] = '\0';
+		if (path[1] == '\0')
+			return (resolved);
+		resolved_len = 1;
+		left_len = strlcpy(left, path + 1, sizeof(left));
+	} else {
+		if (getcwd(resolved, PATH_MAX) == NULL) {
+			if (mem_allocated)
+				free(resolved);
+			else
+				strlcpy(resolved, ".", PATH_MAX);
+			return (NULL);
+		}
+		resolved_len = strlen(resolved);
+		left_len = strlcpy(left, path, sizeof(left));
+	}
+	if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
+		errno = ENAMETOOLONG;
+		goto err;
+	}
+
+	/*
+	 * Iterate over path components in `left'.
+	 */
+	while (left_len != 0) {
+		/*
+		 * Extract the next path component and adjust `left'
+		 * and its length.
+		 */
+		p = strchr(left, '/');
+		s = p ? p : left + left_len;
+		if (s - left >= (ptrdiff_t)sizeof(next_token)) {
+			errno = ENAMETOOLONG;
+			goto err;
+		}
+		memcpy(next_token, left, s - left);
+		next_token[s - left] = '\0';
+		left_len -= s - left;
+		if (p != NULL)
+			memmove(left, s + 1, left_len + 1);
+		if (resolved[resolved_len - 1] != '/') {
+			if (resolved_len + 1 >= PATH_MAX) {
+				errno = ENAMETOOLONG;
+				goto err;
+			}
+			resolved[resolved_len++] = '/';
+			resolved[resolved_len] = '\0';
+		}
+		if (next_token[0] == '\0')
+			continue;
+		else if (strcmp(next_token, ".") == 0)
+			continue;
+		else if (strcmp(next_token, "..") == 0) {
+			/*
+			 * Strip the last path component except when we have
+			 * single "/"
+			 */
+			if (resolved_len > 1) {
+				resolved[resolved_len - 1] = '\0';
+				q = strrchr(resolved, '/') + 1;
+				*q = '\0';
+				resolved_len = q - resolved;
+			}
+			continue;
+		}
+
+		/*
+		 * Append the next path component and lstat() it. If
+		 * lstat() fails we still can return successfully if
+		 * there are no more path components left.
+		 */
+		resolved_len = strlcat(resolved, next_token, PATH_MAX);
+		if (resolved_len >= PATH_MAX) {
+			errno = ENAMETOOLONG;
+			goto err;
+		}
+		if (lstat(resolved, &sb) != 0) {
+			if (errno == ENOENT && p == NULL) {
+				errno = serrno;
+				return (resolved);
+			}
+			goto err;
+		}
+		if (S_ISLNK(sb.st_mode)) {
+			if (symlinks++ > SYMLOOP_MAX) {
+				errno = ELOOP;
+				goto err;
+			}
+			slen = readlink(resolved, symlink, sizeof(symlink) - 1);
+			if (slen < 0)
+				goto err;
+			symlink[slen] = '\0';
+			if (symlink[0] == '/') {
+				resolved[1] = 0;
+				resolved_len = 1;
+			} else if (resolved_len > 1) {
+				/* Strip the last path component. */
+				resolved[resolved_len - 1] = '\0';
+				q = strrchr(resolved, '/') + 1;
+				*q = '\0';
+				resolved_len = q - resolved;
+			}
+
+			/*
+			 * If there are any path components left, then
+			 * append them to symlink. The result is placed
+			 * in `left'.
+			 */
+			if (p != NULL) {
+				if (symlink[slen - 1] != '/') {
+					if (slen + 1 >=
+					    (ptrdiff_t)sizeof(symlink)) {
+						errno = ENAMETOOLONG;
+						goto err;
+					}
+					symlink[slen] = '/';
+					symlink[slen + 1] = 0;
+				}
+				left_len = strlcat(symlink, left, sizeof(symlink));
+				if (left_len >= sizeof(symlink)) {
+					errno = ENAMETOOLONG;
+					goto err;
+				}
+			}
+			left_len = strlcpy(left, symlink, sizeof(left));
+		}
+	}
+
+	/*
+	 * Remove trailing slash except when the resolved pathname
+	 * is a single "/".
+	 */
+	if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
+		resolved[resolved_len - 1] = '\0';
+	return (resolved);
+
+err:
+	if (mem_allocated)
+		free(resolved);
+	return (NULL);
+}