Fixes https://github.com/NixOS/nixpkgs/issues/140735. Co-authored-by: Jörg Thalheim <Mic92@users.noreply.github.com>
296 lines
8.3 KiB
C
296 lines
8.3 KiB
C
#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdarg.h>
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#include <stdlib.h>
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#include <dlfcn.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <string.h>
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#include <spawn.h>
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#include <dirent.h>
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#define MAX_REDIRECTS 128
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static int nrRedirects = 0;
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static char * from[MAX_REDIRECTS];
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static char * to[MAX_REDIRECTS];
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static int isInitialized = 0;
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// FIXME: might run too late.
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static void init() __attribute__((constructor));
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static void init()
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{
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if (isInitialized) return;
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char * spec = getenv("NIX_REDIRECTS");
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if (!spec) return;
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// Ensure we only run this code once.
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// We do not do `unsetenv("NIX_REDIRECTS")` to ensure that redirects
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// also get initialized for subprocesses.
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isInitialized = 1;
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char * spec2 = malloc(strlen(spec) + 1);
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strcpy(spec2, spec);
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char * pos = spec2, * eq;
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while ((eq = strchr(pos, '='))) {
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*eq = 0;
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from[nrRedirects] = pos;
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pos = eq + 1;
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to[nrRedirects] = pos;
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nrRedirects++;
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if (nrRedirects == MAX_REDIRECTS) break;
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char * end = strchr(pos, ':');
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if (!end) break;
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*end = 0;
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pos = end + 1;
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}
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}
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static const char * rewrite(const char * path, char * buf)
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{
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if (path == NULL) return path;
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for (int n = 0; n < nrRedirects; ++n) {
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int len = strlen(from[n]);
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if (strncmp(path, from[n], len) != 0) continue;
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if (snprintf(buf, PATH_MAX, "%s%s", to[n], path + len) >= PATH_MAX)
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abort();
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return buf;
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}
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return path;
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}
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static int open_needs_mode(int flags)
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{
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#ifdef O_TMPFILE
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return (flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE;
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#else
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return flags & O_CREAT;
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#endif
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}
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/* The following set of Glibc library functions is very incomplete -
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it contains only what we needed for programs in Nixpkgs. Just add
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more functions as needed. */
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int open(const char * path, int flags, ...)
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{
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int (*open_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open");
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mode_t mode = 0;
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if (open_needs_mode(flags)) {
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va_list ap;
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va_start(ap, flags);
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mode = va_arg(ap, mode_t);
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va_end(ap);
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}
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char buf[PATH_MAX];
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return open_real(rewrite(path, buf), flags, mode);
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}
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int open64(const char * path, int flags, ...)
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{
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int (*open64_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open64");
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mode_t mode = 0;
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if (open_needs_mode(flags)) {
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va_list ap;
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va_start(ap, flags);
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mode = va_arg(ap, mode_t);
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va_end(ap);
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}
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char buf[PATH_MAX];
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return open64_real(rewrite(path, buf), flags, mode);
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}
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int openat(int dirfd, const char * path, int flags, ...)
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{
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int (*openat_real) (int, const char *, int, mode_t) = dlsym(RTLD_NEXT, "openat");
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mode_t mode = 0;
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if (open_needs_mode(flags)) {
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va_list ap;
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va_start(ap, flags);
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mode = va_arg(ap, mode_t);
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va_end(ap);
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}
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char buf[PATH_MAX];
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return openat_real(dirfd, rewrite(path, buf), flags, mode);
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}
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FILE * fopen(const char * path, const char * mode)
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{
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FILE * (*fopen_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen");
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char buf[PATH_MAX];
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return fopen_real(rewrite(path, buf), mode);
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}
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FILE * __nss_files_fopen(const char * path)
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{
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FILE * (*__nss_files_fopen_real) (const char *) = dlsym(RTLD_NEXT, "__nss_files_fopen");
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char buf[PATH_MAX];
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return __nss_files_fopen_real(rewrite(path, buf));
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}
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FILE * fopen64(const char * path, const char * mode)
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{
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FILE * (*fopen64_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen64");
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char buf[PATH_MAX];
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return fopen64_real(rewrite(path, buf), mode);
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}
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int __xstat(int ver, const char * path, struct stat * st)
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{
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int (*__xstat_real) (int ver, const char *, struct stat *) = dlsym(RTLD_NEXT, "__xstat");
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char buf[PATH_MAX];
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return __xstat_real(ver, rewrite(path, buf), st);
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}
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int __xstat64(int ver, const char * path, struct stat64 * st)
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{
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int (*__xstat64_real) (int ver, const char *, struct stat64 *) = dlsym(RTLD_NEXT, "__xstat64");
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char buf[PATH_MAX];
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return __xstat64_real(ver, rewrite(path, buf), st);
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}
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int stat(const char * path, struct stat * st)
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{
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int (*__stat_real) (const char *, struct stat *) = dlsym(RTLD_NEXT, "stat");
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char buf[PATH_MAX];
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return __stat_real(rewrite(path, buf), st);
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}
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int access(const char * path, int mode)
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{
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int (*access_real) (const char *, int mode) = dlsym(RTLD_NEXT, "access");
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char buf[PATH_MAX];
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return access_real(rewrite(path, buf), mode);
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}
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int posix_spawn(pid_t * pid, const char * path,
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const posix_spawn_file_actions_t * file_actions,
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const posix_spawnattr_t * attrp,
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char * const argv[], char * const envp[])
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{
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int (*posix_spawn_real) (pid_t *, const char *,
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const posix_spawn_file_actions_t *,
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const posix_spawnattr_t *,
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char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawn");
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char buf[PATH_MAX];
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return posix_spawn_real(pid, rewrite(path, buf), file_actions, attrp, argv, envp);
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}
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int posix_spawnp(pid_t * pid, const char * file,
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const posix_spawn_file_actions_t * file_actions,
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const posix_spawnattr_t * attrp,
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char * const argv[], char * const envp[])
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{
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int (*posix_spawnp_real) (pid_t *, const char *,
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const posix_spawn_file_actions_t *,
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const posix_spawnattr_t *,
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char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawnp");
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char buf[PATH_MAX];
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return posix_spawnp_real(pid, rewrite(file, buf), file_actions, attrp, argv, envp);
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}
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int execv(const char * path, char * const argv[])
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{
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int (*execv_real) (const char * path, char * const argv[]) = dlsym(RTLD_NEXT, "execv");
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char buf[PATH_MAX];
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return execv_real(rewrite(path, buf), argv);
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}
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int execvp(const char * path, char * const argv[])
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{
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int (*_execvp) (const char *, char * const argv[]) = dlsym(RTLD_NEXT, "execvp");
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char buf[PATH_MAX];
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return _execvp(rewrite(path, buf), argv);
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}
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int execve(const char * path, char * const argv[], char * const envp[])
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{
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int (*_execve) (const char *, char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "execve");
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char buf[PATH_MAX];
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return _execve(rewrite(path, buf), argv, envp);
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}
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DIR * opendir(const char * path)
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{
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char buf[PATH_MAX];
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DIR * (*_opendir) (const char*) = dlsym(RTLD_NEXT, "opendir");
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return _opendir(rewrite(path, buf));
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}
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#define SYSTEM_CMD_MAX 512
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char *replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
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char head[SYSTEM_CMD_MAX] = {0};
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strncpy(head, source, start_ptr - source);
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char tail[SYSTEM_CMD_MAX] = {0};
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if(suffix_ptr < source + strlen(source)) {
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strcpy(tail, suffix_ptr);
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}
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sprintf(buf, "%s%s%s", head, replace_string, tail);
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return buf;
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}
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char *replace_string(char * buf, char * from, char * to) {
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int num_matches = 0;
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char * matches[SYSTEM_CMD_MAX];
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int from_len = strlen(from);
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for(int i=0; i<strlen(buf); i++){
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char *cmp_start = buf + i;
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if(strncmp(from, cmp_start, from_len) == 0){
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matches[num_matches] = cmp_start;
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num_matches++;
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}
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}
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int len_diff = strlen(to) - strlen(from);
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for(int n = 0; n < num_matches; n++) {
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char replaced[SYSTEM_CMD_MAX];
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replace_substring(buf, replaced, to, matches[n], matches[n]+from_len);
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strcpy(buf, replaced);
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for(int nn = n+1; nn < num_matches; nn++) {
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matches[nn] += len_diff;
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}
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}
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return buf;
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}
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void rewriteSystemCall(const char * command, char * buf) {
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strcpy(buf, command);
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for (int n = 0; n < nrRedirects; ++n) {
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replace_string(buf, from[n], to[n]);
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}
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}
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int system(const char *command)
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{
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int (*_system) (const char*) = dlsym(RTLD_NEXT, "system");
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char newCommand[SYSTEM_CMD_MAX];
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rewriteSystemCall(command, newCommand);
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return _system(newCommand);
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}
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int mkdir(const char *path, mode_t mode)
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{
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int (*mkdir_real) (const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdir");
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char buf[PATH_MAX];
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return mkdir_real(rewrite(path, buf), mode);
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}
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int mkdirat(int dirfd, const char *path, mode_t mode)
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{
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int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdirat");
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char buf[PATH_MAX];
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return mkdirat_real(dirfd, rewrite(path, buf), mode);
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}
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