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Diffstat (limited to '')
| -rw-r--r-- | sftp-realpath.c | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/sftp-realpath.c b/sftp-realpath.c new file mode 100644 index 0000000..2ec779d --- /dev/null +++ b/sftp-realpath.c @@ -0,0 +1,225 @@ +/* $OpenBSD: sftp-realpath.c,v 1.2 2021/09/02 21:03:54 deraadt 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 "includes.h" + +#include <sys/types.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); +} |