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);
+}