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Mini Shell
Mini Shell
#include <string.h>
#include "uv.h"
#include "uvwasi.h"
#include "uvwasi_alloc.h"
#include "uv_mapping.h"
#include "path_resolver.h"
#define UVWASI__MAX_SYMLINK_FOLLOWS 32
#ifndef _WIN32
# define IS_SLASH(c) ((c) == '/')
#else
# define IS_SLASH(c) ((c) == '/' || (c) == '\\')
#endif /* _WIN32 */
static int uvwasi__is_absolute_path(const char* path, uvwasi_size_t path_len) {
/* It's expected that only Unix style paths will be generated by WASI. */
return path != NULL && path_len > 0 && path[0] == '/';
}
static char* uvwasi__strchr_slash(const char* s) {
/* strchr() that identifies /, as well as \ on Windows. */
do {
if (IS_SLASH(*s))
return (char*) s;
} while (*s++);
return NULL;
}
static uvwasi_errno_t uvwasi__combine_paths(const uvwasi_t* uvwasi,
const char* path1,
uvwasi_size_t path1_len,
const char* path2,
uvwasi_size_t path2_len,
char** combined_path,
uvwasi_size_t* combined_len) {
/* This function joins two paths with '/'. */
uvwasi_errno_t err;
char* combined;
int combined_size;
int r;
*combined_path = NULL;
*combined_len = 0;
/* The max combined size is the path1 length + the path2 length
+ 2 for a terminating NULL and a possible path separator. */
combined_size = path1_len + path2_len + 2;
combined = uvwasi__malloc(uvwasi, combined_size);
if (combined == NULL) return UVWASI_ENOMEM;
r = snprintf(combined, combined_size, "%s/%s", path1, path2);
if (r <= 0) {
err = uvwasi__translate_uv_error(uv_translate_sys_error(errno));
goto exit;
}
err = UVWASI_ESUCCESS;
*combined_path = combined;
*combined_len = strlen(combined);
exit:
if (err != UVWASI_ESUCCESS) uvwasi__free(uvwasi, combined);
return err;
}
uvwasi_errno_t uvwasi__normalize_path(const char* path,
uvwasi_size_t path_len,
char* normalized_path,
uvwasi_size_t normalized_len) {
const char* cur;
char* ptr;
char* next;
char* last;
size_t cur_len;
int is_absolute;
if (path_len > normalized_len)
return UVWASI_ENOBUFS;
is_absolute = uvwasi__is_absolute_path(path, path_len);
normalized_path[0] = '\0';
ptr = normalized_path;
for (cur = path; cur != NULL; cur = next + 1) {
next = uvwasi__strchr_slash(cur);
cur_len = (next == NULL) ? strlen(cur) : (size_t) (next - cur);
if (cur_len == 0) {
if (ptr == normalized_path && next != NULL && is_absolute) {
*ptr = '/';
ptr++;
}
*ptr = '\0';
} else if (cur_len == 1 && cur[0] == '.') {
/* No-op. Just consume the '.' */
} else if (cur_len == 2 && cur[0] == '.' && cur[1] == '.') {
/* Identify the path segment that preceded the current one. */
last = ptr;
while (!IS_SLASH(*last) && last != normalized_path) {
last--;
}
/* If the result is currently empty, or the last prior path is also '..'
then output '..'. Otherwise, remove the last path segment. */
if (ptr == normalized_path ||
(last == ptr - 2 && last[0] == '.' && last[1] == '.') ||
(last == ptr - 3 && last[0] == '/' &&
last[1] == '.' && last[2] == '.')) {
if (ptr != normalized_path && *(ptr - 1) != '/') {
*ptr = '/';
ptr++;
}
*ptr = '.';
ptr++;
*ptr = '.';
ptr++;
} else {
/* Strip the last segment, but make sure not to strip the '/' if that
is the entire path. */
if (last == normalized_path && *last == '/')
ptr = last + 1;
else
ptr = last;
}
*ptr = '\0';
} else {
if (ptr != normalized_path && *(ptr - 1) != '/') {
*ptr = '/';
ptr++;
}
memcpy(ptr, cur, cur_len);
ptr += cur_len;
*ptr = '\0';
}
if (next == NULL)
break;
}
/* Normalized the path to the empty string. Return either '/' or '.'. */
if (ptr == normalized_path) {
if (1 == is_absolute)
*ptr = '/';
else
*ptr = '.';
ptr++;
*ptr = '\0';
}
return UVWASI_ESUCCESS;
}
static int uvwasi__is_path_sandboxed(const char* path,
uvwasi_size_t path_len,
const char* fd_path,
uvwasi_size_t fd_path_len) {
char* ptr;
int remaining_len;
if (1 == uvwasi__is_absolute_path(fd_path, fd_path_len))
return path == strstr(path, fd_path) ? 1 : 0;
/* Handle relative fds that normalized to '.' */
if (fd_path_len == 1 && fd_path[0] == '.') {
/* If the fd's path is '.', then any path does not begin with '..' is OK. */
if ((path_len == 2 && path[0] == '.' && path[1] == '.') ||
(path_len > 2 && path[0] == '.' && path[1] == '.' && path[2] == '/')) {
return 0;
}
return 1;
}
if (path != strstr(path, fd_path))
return 0;
/* Fail if the remaining path starts with '..', '../', '/..', or '/../'. */
ptr = (char*) path + fd_path_len;
remaining_len = path_len - fd_path_len;
if (remaining_len < 2)
return 1;
/* Strip a leading slash so the check is only for '..' and '../'. */
if (*ptr == '/') {
ptr++;
remaining_len--;
}
if ((remaining_len == 2 && ptr[0] == '.' && ptr[1] == '.') ||
(remaining_len > 2 && ptr[0] == '.' && ptr[1] == '.' && ptr[2] == '/')) {
return 0;
}
return 1;
}
static uvwasi_errno_t uvwasi__normalize_absolute_path(
const uvwasi_t* uvwasi,
const struct uvwasi_fd_wrap_t* fd,
const char* path,
uvwasi_size_t path_len,
char** normalized_path,
uvwasi_size_t* normalized_len
) {
/* This function resolves an absolute path to the provided file descriptor.
If the file descriptor's path is relative, then this operation will fail
with UVWASI_ENOTCAPABLE since it doesn't make sense to resolve an absolute
path to a relative prefix. If the file desciptor's path is also absolute,
then we just need to verify that the normalized path still starts with
the file descriptor's path. */
uvwasi_errno_t err;
char* abs_path;
int abs_size;
*normalized_path = NULL;
*normalized_len = 0;
abs_size = path_len + 1;
abs_path = uvwasi__malloc(uvwasi, abs_size);
if (abs_path == NULL) {
err = UVWASI_ENOMEM;
goto exit;
}
/* Normalize the input path first. */
err = uvwasi__normalize_path(path, path_len, abs_path, path_len);
if (err != UVWASI_ESUCCESS)
goto exit;
/* Once the input is normalized, ensure that it is still sandboxed. */
if (0 == uvwasi__is_path_sandboxed(abs_path,
path_len,
fd->normalized_path,
strlen(fd->normalized_path))) {
err = UVWASI_ENOTCAPABLE;
goto exit;
}
*normalized_path = abs_path;
*normalized_len = abs_size - 1;
return UVWASI_ESUCCESS;
exit:
uvwasi__free(uvwasi, abs_path);
return err;
}
static uvwasi_errno_t uvwasi__normalize_relative_path(
const uvwasi_t* uvwasi,
const struct uvwasi_fd_wrap_t* fd,
const char* path,
uvwasi_size_t path_len,
char** normalized_path,
uvwasi_size_t* normalized_len
) {
/* This function resolves a relative path to the provided file descriptor.
The relative path is concatenated to the file descriptor's path, and then
normalized. */
uvwasi_errno_t err;
char* combined;
char* normalized;
uvwasi_size_t combined_len;
uvwasi_size_t fd_path_len;
uvwasi_size_t norm_len;
*normalized_path = NULL;
*normalized_len = 0;
fd_path_len = strlen(fd->normalized_path);
err = uvwasi__combine_paths(uvwasi,
fd->normalized_path,
fd_path_len,
path,
path_len,
&combined,
&combined_len);
if (err != UVWASI_ESUCCESS) goto exit;
normalized = uvwasi__malloc(uvwasi, combined_len + 1);
if (normalized == NULL) {
err = UVWASI_ENOMEM;
goto exit;
}
/* Normalize the input path. */
err = uvwasi__normalize_path(combined,
combined_len,
normalized,
combined_len);
if (err != UVWASI_ESUCCESS)
goto exit;
norm_len = strlen(normalized);
/* Once the path is normalized, ensure that it is still sandboxed. */
if (0 == uvwasi__is_path_sandboxed(normalized,
norm_len,
fd->normalized_path,
fd_path_len)) {
err = UVWASI_ENOTCAPABLE;
goto exit;
}
err = UVWASI_ESUCCESS;
*normalized_path = normalized;
*normalized_len = norm_len;
exit:
if (err != UVWASI_ESUCCESS)
uvwasi__free(uvwasi, normalized);
uvwasi__free(uvwasi, combined);
return err;
}
static uvwasi_errno_t uvwasi__resolve_path_to_host(
const uvwasi_t* uvwasi,
const struct uvwasi_fd_wrap_t* fd,
const char* path,
uvwasi_size_t path_len,
char** resolved_path,
uvwasi_size_t* resolved_len
) {
/* Return the normalized path, but resolved to the host's real path. */
char* res_path;
char* stripped_path;
int real_path_len;
int fake_path_len;
int stripped_len;
#ifdef _WIN32
uvwasi_size_t i;
#endif /* _WIN32 */
real_path_len = strlen(fd->real_path);
fake_path_len = strlen(fd->normalized_path);
/* If the fake path is '.' just ignore it. */
if (fake_path_len == 1 && fd->normalized_path[0] == '.') {
fake_path_len = 0;
}
stripped_len = path_len - fake_path_len;
/* The resolved path's length is calculated as: the length of the fd's real
path, + 1 for a path separator, and the length of the input path (with the
fake path stripped off). */
*resolved_len = stripped_len + real_path_len + 1;
*resolved_path = uvwasi__malloc(uvwasi, *resolved_len + 1);
if (*resolved_path == NULL)
return UVWASI_ENOMEM;
res_path = *resolved_path;
stripped_path = (char*) path + fake_path_len;
memcpy(res_path, fd->real_path, real_path_len);
res_path += real_path_len;
if (stripped_len > 1 ||
(stripped_len == 1 && stripped_path[0] != '/')) {
if (stripped_path[0] != '/') {
*res_path = '/';
res_path++;
}
memcpy(res_path, stripped_path, stripped_len);
res_path += stripped_len;
}
*res_path = '\0';
#ifdef _WIN32
/* Replace / with \ on Windows. */
res_path = *resolved_path;
for (i = real_path_len; i < *resolved_len; i++) {
if (res_path[i] == '/')
res_path[i] = '\\';
}
#endif /* _WIN32 */
return UVWASI_ESUCCESS;
}
uvwasi_errno_t uvwasi__resolve_path(const uvwasi_t* uvwasi,
const struct uvwasi_fd_wrap_t* fd,
const char* path,
uvwasi_size_t path_len,
char** resolved_path,
uvwasi_lookupflags_t flags) {
uv_fs_t req;
uvwasi_errno_t err;
const char* input;
char* host_path;
char* normalized_path;
char* link_target;
char* normalized_parent;
char* resolved_link_target;
uvwasi_size_t input_len;
uvwasi_size_t host_path_len;
uvwasi_size_t normalized_len;
uvwasi_size_t link_target_len;
uvwasi_size_t normalized_parent_len;
uvwasi_size_t resolved_link_target_len;
int follow_count;
int r;
input = path;
input_len = path_len;
link_target = NULL;
follow_count = 0;
host_path = NULL;
normalized_parent = NULL;
resolved_link_target = NULL;
start:
normalized_path = NULL;
err = UVWASI_ESUCCESS;
if (1 == uvwasi__is_absolute_path(input, input_len)) {
err = uvwasi__normalize_absolute_path(uvwasi,
fd,
input,
input_len,
&normalized_path,
&normalized_len);
} else {
err = uvwasi__normalize_relative_path(uvwasi,
fd,
input,
input_len,
&normalized_path,
&normalized_len);
}
if (err != UVWASI_ESUCCESS)
goto exit;
uvwasi__free(uvwasi, host_path);
err = uvwasi__resolve_path_to_host(uvwasi,
fd,
normalized_path,
normalized_len,
&host_path,
&host_path_len);
if (err != UVWASI_ESUCCESS)
goto exit;
if ((flags & UVWASI_LOOKUP_SYMLINK_FOLLOW) == UVWASI_LOOKUP_SYMLINK_FOLLOW) {
r = uv_fs_readlink(NULL, &req, host_path, NULL);
if (r != 0) {
#ifdef _WIN32
/* uv_fs_readlink() returns UV__UNKNOWN on Windows. Try to get a better
error using uv_fs_stat(). */
if (r == UV__UNKNOWN) {
uv_fs_req_cleanup(&req);
r = uv_fs_stat(NULL, &req, host_path, NULL);
if (r == 0) {
if (uvwasi__stat_to_filetype(&req.statbuf) !=
UVWASI_FILETYPE_SYMBOLIC_LINK) {
r = UV_EINVAL;
}
}
/* Fall through. */
}
#endif /* _WIN32 */
/* Don't report UV_EINVAL or UV_ENOENT. They mean that either the file
does not exist, or it is not a symlink. Both are OK. */
if (r != UV_EINVAL && r != UV_ENOENT)
err = uvwasi__translate_uv_error(r);
uv_fs_req_cleanup(&req);
goto exit;
}
/* Clean up memory and follow the link, unless it's time to return ELOOP. */
follow_count++;
if (follow_count >= UVWASI__MAX_SYMLINK_FOLLOWS) {
uv_fs_req_cleanup(&req);
err = UVWASI_ELOOP;
goto exit;
}
link_target_len = strlen(req.ptr);
uvwasi__free(uvwasi, link_target);
link_target = uvwasi__malloc(uvwasi, link_target_len + 1);
if (link_target == NULL) {
uv_fs_req_cleanup(&req);
err = UVWASI_ENOMEM;
goto exit;
}
memcpy(link_target, req.ptr, link_target_len + 1);
uv_fs_req_cleanup(&req);
if (1 == uvwasi__is_absolute_path(link_target, link_target_len)) {
input = link_target;
input_len = link_target_len;
} else {
uvwasi__free(uvwasi, normalized_parent);
uvwasi__free(uvwasi, resolved_link_target);
err = uvwasi__combine_paths(uvwasi,
normalized_path,
normalized_len,
"..",
2,
&normalized_parent,
&normalized_parent_len);
if (err != UVWASI_ESUCCESS) goto exit;
err = uvwasi__combine_paths(uvwasi,
normalized_parent,
normalized_parent_len,
link_target,
link_target_len,
&resolved_link_target,
&resolved_link_target_len);
if (err != UVWASI_ESUCCESS) goto exit;
input = resolved_link_target;
input_len = resolved_link_target_len;
}
uvwasi__free(uvwasi, normalized_path);
goto start;
}
exit:
if (err == UVWASI_ESUCCESS) {
*resolved_path = host_path;
} else {
*resolved_path = NULL;
uvwasi__free(uvwasi, host_path);
}
uvwasi__free(uvwasi, link_target);
uvwasi__free(uvwasi, normalized_path);
uvwasi__free(uvwasi, normalized_parent);
uvwasi__free(uvwasi, resolved_link_target);
return err;
}
Zerion Mini Shell 1.0