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Cider Isn't Darwin Emulation, Really
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#include <lkm/api.h>#ifdef TEST# include <unistd.h># include <sys/stat.h># include <sys/syscall.h># include <stdio.h># include <stdbool.h># include <stdlib.h># include <string.h># include <errno.h># include <dirent.h># include <fcntl.h>
# define LINUX_SYSCALL(...) ({ int __rv = syscall(__VA_ARGS__); if (__rv == -1) __rv = -errno; __rv; })# define LINUX_ENOENT ENOENT# define LINUX_ELOOP ELOOP# define LINUX_ENAMETOOLONG ENAMETOOLONG
# define LINUX_S_IFMT S_IFMT# define LINUX_S_IFLNK S_IFLNK
# define LINUX_O_RDONLY O_RDONLY
# define __simple_sprintf sprintf# define linux_dirent64 direnttypedef struct stat stat_t;#else# include "base.h"# include <mach/lkm.h># include <linux-syscalls/linux.h># include <fcntl/open.h># include "simple.h"# include <stdbool.h># include "errno.h"# include "duct_errno.h"# include "stat/common.h"# include "dirent/getdirentries.h"typedef struct linux_stat stat_t;
extern __SIZE_TYPE__ strlen(const char* s);extern char* strcpy(char* dest, const char* src);extern int strcmp(const char* str1, const char* str2);extern int strncmp(const char* str1, const char* str2, __SIZE_TYPE__ n);extern int strncasecmp(const char* str1, const char* str2, __SIZE_TYPE__ n);extern int strcasecmp(const char* str1, const char* str2);extern void *memcpy(void *dest, const void *src, __SIZE_TYPE__ n);
#define LINUX_S_IFMT 00170000#define LINUX_S_IFLNK 0120000
// #define __simple_printf(...)#define __simple_printf __simple_kprintf // For bug hunting
#endif
static bool next_component(const char* from, const char** end);
static char prefix_path[4096] = {0}; // MUST NOT end with '/'static int prefix_path_len = -1;
static const char EXIT_PATH[] = "/Volumes/SystemRoot";
#ifndef TEST#ifdef VARIANT_DYLD#define icase_enabled false#else#define icase_enabled true#endif
#elsestatic bool icase_enabled = true;#endif
static const int MAX_SYMLINK_DEPTH = 10;
struct context{ const char* current_root; int current_root_len;
char current_path[4096]; int current_path_len;
int symlink_depth; bool unknown_component; bool follow;};
static int vchroot_run(const char* path, struct context* ctxt);
#ifndef TESTVISIBLE#endifint __darling_vchroot(int dfd){ int rv;
#ifndef TEST rv = lkm_call(NR_vchroot, dfd); if (rv != 0) return rv;#endif
char buf[50];
__simple_sprintf(buf, "/proc/self/fd/%d", dfd);
rv = LINUX_SYSCALL(__NR_readlink, buf, prefix_path, sizeof(prefix_path) - 1); prefix_path[rv] = '\0'; prefix_path_len = rv;
return 0;}
#ifndef TESTVISIBLEint __darling_vchroot_expand(const char* path, char* out){ struct vchroot_expand_args a = { .dfd = -100, .flags = 0 };
strcpy(a.path, path);
int rv = vchroot_expand(&a);
strcpy(out, a.path); return rv;}#endif
static void init_vchroot_path(void){ struct vchroot_expand_args a = { .path = "/", .dfd = -100, .flags = 0 };
lkm_call(NR_vchroot_expand, &a); int len = strlen(a.path); if (len > 0 && a.path[len-1] == '/') a.path[--len] = '\0'; strcpy(prefix_path, a.path); prefix_path_len = len;
#ifndef TEST __simple_printf("init_vchroot_path: %s\n", prefix_path);#endif}
int vchroot_expand(struct vchroot_expand_args* args){ struct context ctxt;
#ifndef TEST if (prefix_path_len == -1) init_vchroot_path(); __simple_printf("vchroot_expand(): input %s\n", args->path);#endif
ctxt.unknown_component = false; ctxt.symlink_depth = 0; ctxt.current_root = prefix_path; ctxt.current_root_len = prefix_path_len; ctxt.follow = !!(args->flags & VCHROOT_FOLLOW);
const char* input_path = args->path;
if (*input_path != '/') { char buf[50];
if (args->dfd != -100) __simple_sprintf(buf, "/proc/self/fd/%d", args->dfd); else strcpy(buf, "/proc/self/cwd");
int rv = LINUX_SYSCALL(__NR_readlink, buf, ctxt.current_path, sizeof(ctxt.current_path) - 1);
if (rv < 0) {#ifndef TEST __simple_printf(" dfd %d -> err %d!\n", args->dfd, rv);#endif return rv; } // If we got "/", then turn it into "", because our algorithm will add a trailing slash later if (rv == 1 && ctxt.current_path[0] == '/') { ctxt.current_path[0] = '\0'; ctxt.current_path_len = 0; } else { ctxt.current_path_len = rv; ctxt.current_path[rv] = '\0'; }
// Are we outside the vchrooted area already? if (ctxt.current_path_len < ctxt.current_root_len || strncmp(ctxt.current_path, ctxt.current_root, ctxt.current_root_len) != 0) { ctxt.current_root = ""; ctxt.current_root_len = 0; } }
int rv = vchroot_run(input_path, &ctxt); if (ctxt.current_path_len > 0) strcpy(args->path, ctxt.current_path); else strcpy(args->path, "/");
#ifndef TEST __simple_printf(" vchroot_expand(): rv=%d, expanded to %s\n", rv, args->path);#endif
return rv;}
static int vchroot_run(const char* input_path, struct context* ctxt){ if (ctxt->symlink_depth > MAX_SYMLINK_DEPTH) return -LINUX_ELOOP;
if (*input_path == '/') { strcpy(ctxt->current_path, ctxt->current_root); ctxt->current_path_len = strlen(ctxt->current_path); input_path++; }
const char* end; while (next_component(input_path, &end)) { const unsigned int len = end - input_path;
if ((len == 1 && input_path[0] == '.') || len == 0) // . or nothing (//) { // nothing to do } else { // append / ctxt->current_path[ctxt->current_path_len++] = '/'; ctxt->current_path[ctxt->current_path_len] = '\0';
if (len == 2 && input_path[0] == '.' && input_path[1] == '.') // .. { // Returning back into the vchrooted area if (ctxt->current_path_len <= 1) { strcpy(ctxt->current_path, prefix_path); strcat(ctxt->current_path, EXIT_PATH); ctxt->current_path_len = prefix_path_len + sizeof(EXIT_PATH);
ctxt->current_path[ctxt->current_path_len-1] = '/'; ctxt->current_path[ctxt->current_path_len] = '\0';
ctxt->current_root = prefix_path; ctxt->current_root_len = prefix_path_len; }
// current_path always ends with a slash // p points before the last / char* p = ctxt->current_path + ctxt->current_path_len - 2;
while (true) { if (*p == '/') { *p = '\0'; ctxt->current_path_len = p - ctxt->current_path;
// We cannot exit current_root via .. if (ctxt->current_path_len < ctxt->current_root_len) return -LINUX_ENOENT; break; } p--; } } else { if (len + ctxt->current_path_len + 2 > sizeof(ctxt->current_path)) return -LINUX_ENOENT; // Append the component const int prevlen = ctxt->current_path_len;
memcpy(ctxt->current_path + ctxt->current_path_len, input_path, len); ctxt->current_path_len += len; ctxt->current_path[ctxt->current_path_len] = '\0';
// Only analyze the last path component if we haven't had an unresolvent ENOENT before if (!ctxt->unknown_component) { stat_t st; int status = LINUX_SYSCALL(__NR_lstat, ctxt->current_path, &st);
if (icase_enabled && status == -LINUX_ENOENT) { // Case insensitive search
// Examine the directory above ctxt->current_path[prevlen-1] = '\0';
int dfd = LINUX_SYSCALL(__NR_open, (prevlen > 1) ? ctxt->current_path : "/", LINUX_O_RDONLY); char dirents[4096]; // buffer space for struct linux_dirent64 entries int len;
if (dfd < 0) { ctxt->unknown_component = true; goto done_getdents; } // Get a batch of directory entries while ((len = LINUX_SYSCALL(__NR_getdents64, dfd, dirents, sizeof(dirents))) > 0) { int pos = 0;
// Iterate through directory entries while (pos < len) { struct linux_dirent64* de = (struct linux_dirent64*) &dirents[pos]; if (strcasecmp(de->d_name, ctxt->current_path + prevlen) == 0) { // Fix up the case and be done with it strcpy(ctxt->current_path + prevlen, de->d_name); goto done_getdents; } pos += de->d_reclen; } } ctxt->unknown_component = true;done_getdents: // Restore the / we removed a few lines above ctxt->current_path[prevlen-1] = '/'; LINUX_SYSCALL(__NR_close, dfd); } else if (status == 0 && (st.st_mode & LINUX_S_IFMT) == LINUX_S_IFLNK) { // Follow symlink if follow is true or if we haven't reached the end of the input path yet if (ctxt->follow || *end) { char link[512]; int rv;
rv = LINUX_SYSCALL(__NR_readlink, ctxt->current_path, link, sizeof(link) - 1);
if (rv < 0) return rv;
link[rv] = '\0';
// Remove the last component (because it will be substituted with symlink contents) if (link[0] != '/') // Only bother to do that if we know that the symlink is not absolute { ctxt->current_path_len = prevlen - 1; // kill the last slash as well ctxt->current_path[ctxt->current_path_len] = '\0'; }
// Symbolic link resolution const bool orig_follow = ctxt->follow;
ctxt->follow = true; ctxt->symlink_depth++;
rv = vchroot_run(link, ctxt);
ctxt->symlink_depth--; ctxt->follow = orig_follow;
if (rv != 0) return rv; } } }
if (ctxt->current_root_len > 0 && ctxt->current_path_len - ctxt->current_root_len == sizeof(EXIT_PATH)-1) { if (strncasecmp(ctxt->current_path + ctxt->current_root_len, EXIT_PATH, sizeof(EXIT_PATH) - 1) == 0) { // Switch to the real system root ctxt->current_path[0] = '\0'; ctxt->current_path_len = 0; ctxt->current_root = ""; ctxt->current_root_len = 0; } } } }
// Move on to the next component input_path = end; while (*input_path == '/') input_path++; }
return 0;}
static bool next_component(const char* from, const char** end){ const char* pos = from; while (*pos != '/' && *pos) pos++; *end = pos; return pos != from;}
int vchroot_fdpath(struct vchroot_fdpath_args* args){#ifndef TEST if (prefix_path_len == -1) init_vchroot_path();#endif
char buf[50]; char link[4096];
__simple_sprintf(buf, "/proc/self/fd/%d", args->fd);
int rv = LINUX_SYSCALL(__NR_readlink, buf, link, sizeof(link) - 1); if (rv < 0) return rv;
link[rv] = '\0';
if (rv >= prefix_path_len && strncmp(link, prefix_path, prefix_path_len) == 0) { if (args->maxlen-1 < rv - prefix_path_len) return -LINUX_ENAMETOOLONG; strcpy(args->path, link + prefix_path_len);
if (args->path[0] == '\0') strcpy(args->path, "/"); } else { if (args->maxlen < sizeof(EXIT_PATH) + rv) return -LINUX_ENAMETOOLONG;
memcpy(args->path, EXIT_PATH, sizeof(EXIT_PATH) - 1); memcpy(args->path + sizeof(EXIT_PATH) - 1, link, rv+1); }
#ifndef TEST __simple_printf("fdpath %d -> %s\n", args->fd, args->path);#endif
return 0;}
#ifdef TESTint main(int argc, const char** argv){ if (argc != 3) { printf("Usage: vchroot_expand <vchroot_dir> <path_to_expand>\n"); return 1; }
int dfd = open(argv[1], O_RDONLY | O_DIRECTORY); __darling_vchroot(dfd); close(dfd);
if (getenv("ICASE")) icase_enabled = true;
struct vchroot_expand_args args; args.dfd = -100; strcpy(args.path, argv[2]);
int rv = vchroot_expand(&args); printf("vchroot_expand() rv = %d\n", rv); printf("-> path = %s\n", args.path);
if (rv == 0) { int fd = open(args.path, O_RDONLY); struct vchroot_fdpath_args fdpath_args; char buf[4096];
fdpath_args.path = buf; fdpath_args.maxlen = sizeof(buf); fdpath_args.fd = fd;
rv = vchroot_fdpath(&fdpath_args);
printf("vchroot_fdpath() rv = %d\n", rv); if (rv >= 0) printf("-> path = %s\n", buf);
close(fd); } return 0;}#endif