Revert "fix: static build + new syscall spoofer"

This reverts commit 197cc3098d.

Makefile

@@ -72,11 +72,11 @@ host: $(HOST_EXE) $(HOST_EXE_SPOOFER)
 
 # Build the main challenge executable
 $(HOST_EXE): $(HOST_SRC) | $(BUILD_DIR)
-	$(HOST_CC) $(HOST_CFLAGS) $(HOST_LDFLAGS) -static $(HOST_INCLUDE) $(HOST_SRC) -o $@
+	$(HOST_CC) $(HOST_CFLAGS) $(HOST_LDFLAGS) $(HOST_INCLUDE) $(HOST_SRC) -o $@
 
 # Build the spoofer
 $(HOST_EXE_SPOOFER): $(HOST_SRC_SPOOFER) | $(BUILD_DIR)
-	$(HOST_CC) $(HOST_CFLAGS) $(HOST_LDFLAGS) -static $^ -o $@ -ldl
+	$(HOST_CC) $(HOST_CFLAGS) $(HOST_LDFLAGS) -shared -fPIC $^ -o $@ -ldl
 
 # Build the encryptor
 $(HOST_EXE_ENCRYPTOR): $(HOST_SRC_ENCRYPTOR) | $(BUILD_DIR)

src/spoof/spoofer.c

@@ -1,164 +1,40 @@
-#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <errno.h>
+#include <dlfcn.h>
-#include <unistd.h>
-#include <sys/ptrace.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <sys/user.h>
-#include <sys/uio.h>
-#include <sys/syscall.h>
-#include <fcntl.h>
 
-static void write_mem(pid_t pid, unsigned long addr, const char *buf, size_t len)
+static FILE *(*real_fopen)(const char *path, const char *mode) = NULL;
-{
+
-    struct iovec local = {(void *)buf, len};
+static void init_real_fopen(void) {
-    struct iovec remote = {(void *)addr, len};
+    if (!real_fopen) {
-    if (process_vm_writev(pid, &local, 1, &remote, 1, 0) < 0)
+        real_fopen = dlsym(RTLD_NEXT, "fopen");
-    {
+        if (!real_fopen) {
-        perror("spoofer: process_vm_writev");
+            fprintf(stderr, "proc_redirect: dlsym(fopen) failed: %s\n", dlerror());
             abort();
         }
     }
-
-static int read_string(pid_t pid, unsigned long addr, char *buf, size_t max)
-{
-    struct iovec local = {buf, max};
-    struct iovec remote = {(void *)addr, max};
-    ssize_t n = process_vm_readv(pid, &local, 1, &remote, 1, 0);
-    if (n < 0)
-        return -1;
-    buf[n < (ssize_t)max ? (size_t)n : max - 1] = '\0';
-    buf[strnlen(buf, max - 1)] = '\0';
-    return 0;
 }
 
-static void handle_openat(pid_t pid, struct user_regs_struct *regs)
+FILE *fopen(const char *path, const char *mode) {
-{
+    init_real_fopen();
-    unsigned long path_ptr = regs->rsi;
-    char orig[4096] = {0};
-    if (read_string(pid, path_ptr, orig, sizeof(orig)) < 0)
-        return;
-    if (strncmp(orig, "/proc/", 6) != 0)
-        return;
 
-    char newpath[4096];
+    if (path && strncmp(path, "/proc/", 6) == 0) {
-    snprintf(newpath, sizeof(newpath), ".%s", orig + 1);
+        const char *rel_suffix = path + 1;
+        size_t len = strlen(rel_suffix) + 4;
+        char *new_path = malloc(len);
+        if (!new_path) {
+            fprintf(stderr, "proc_redirect: malloc failed\n");
+            abort();
+        }
+        new_path[0] = '.';
+        new_path[1] = '/';
+        new_path[2] = '.';
+        strcpy(new_path + 3, rel_suffix);
 
-    /* Scratch space below the red zone, safe from any live stack frame */
+        FILE *f = real_fopen(new_path, mode);
-    unsigned long scratch = regs->rsp - 256 - sizeof(newpath);
+        free(new_path);
-    write_mem(pid, scratch, newpath, strlen(newpath) + 1);
+        return f;
-
-    struct user_regs_struct r = *regs;
-    r.rsi = scratch;
-    if (ptrace(PTRACE_SETREGS, pid, NULL, &r) < 0)
-        perror("spoofer: PTRACE_SETREGS");
-    else
-        fprintf(stderr, "spoofer: redirected '%s' -> '%s'\n", orig, newpath);
     }
 
-int main(int argc, char **argv)
+    return real_fopen(path, mode);
-{
-    if (argc < 2)
-    {
-        fprintf(stderr, "usage: %s <program> [args...]\n", argv[0]);
-        return 1;
-    }
-
-    pid_t pid = fork();
-    if (pid < 0)
-    {
-        perror("fork");
-        return 1;
-    }
-
-    if (pid == 0)
-    {
-        if (ptrace(PTRACE_TRACEME, 0, NULL, NULL) < 0)
-        {
-            perror("spoofer: PTRACE_TRACEME");
-            _exit(1);
-        }
-        execvp(argv[1], argv + 1);
-        perror("spoofer: execvp");
-        _exit(1);
-    }
-
-    int status;
-    if (waitpid(pid, &status, 0) < 0)
-    {
-        perror("waitpid");
-        return 1;
-    }
-    if (!WIFSTOPPED(status))
-    {
-        fprintf(stderr, "spoofer: unexpected initial status %d\n", status);
-        return 1;
-    }
-
-    if (ptrace(PTRACE_SETOPTIONS, pid, NULL,
-               (void *)(long)(PTRACE_O_TRACESYSGOOD | PTRACE_O_EXITKILL)) < 0)
-    {
-        perror("spoofer: PTRACE_SETOPTIONS");
-        return 1;
-    }
-
-    int in_syscall = 0;
-
-    while (1)
-    {
-        if (ptrace(PTRACE_SYSCALL, pid, NULL, NULL) < 0)
-        {
-            perror("spoofer: PTRACE_SYSCALL");
-            break;
-        }
-        if (waitpid(pid, &status, 0) < 0)
-        {
-            perror("waitpid");
-            break;
-        }
-        if (WIFEXITED(status) || WIFSIGNALED(status))
-            break;
-        if (!WIFSTOPPED(status))
-            continue;
-
-        int sig = WSTOPSIG(status);
-
-        if (sig == (SIGTRAP | 0x80))
-        {
-            if (!in_syscall)
-            {
-                struct user_regs_struct regs;
-                if (ptrace(PTRACE_GETREGS, pid, NULL, &regs) == 0)
-                {
-                    if (regs.orig_rax == SYS_openat)
-                    {
-                        handle_openat(pid, &regs);
-                    }
-                    else if (regs.orig_rax == SYS_open)
-                    {
-                        /* SYS_open: rdi=path — copy to rsi so handle_openat works */
-                        regs.rsi = regs.rdi;
-                        handle_openat(pid, &regs);
-                    }
-                }
-            }
-            in_syscall ^= 1;
-        }
-        else
-        {
-            /* Forward real signals to the tracee */
-            ptrace(PTRACE_SYSCALL, pid, NULL, (void *)(long)sig);
-            in_syscall = 0;
-            continue;
-        }
-    }
-
-    if (WIFEXITED(status))
-        return WEXITSTATUS(status);
-    if (WIFSIGNALED(status))
-        return 128 + WTERMSIG(status);
-    return 0;
 }