Added example of program manually mapping the RTLD into its own address space

1 files changed, 78 insertions, 0 deletions

diff --git a/examples/manually_map_rtld.c b/examples/manually_map_rtld.c
new file mode 100644
index 0000000..cfec1e6
--- /dev/null
+++ b/examples/manually_map_rtld.c
@@ -0,0 +1,78 @@
+/* An self-contained example of a program that maps the glibc RTLD into
+   its own address space using open(2) and mmap(2).
+
+   Sizes and offsets are hardcoded to avoid any complicated ELF parsing.
+
+   Copyright (C) 2017 Jakob Kreuze, All Rights Reserved.
+
+   This file is part of Hypodermic.
+
+   Hypodermic is free software: you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation, either version 3 of the License, or (at
+   your option) any later version.
+
+   Hypodermic is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Hypodermic. If not, see <http://www.gnu.org/licenses/>. */
+
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+/* This is going to vary from distro to distro. */
+#define LD_LINUX_PATH "/lib64/ld-2.25.so"
+
+
+int main(void) {
+    int   fd;
+    char  buf;
+    void *ld_text;
+    void *ld_rodata;
+    void *ld_data;
+
+    if ((fd = open(LD_LINUX_PATH, O_RDONLY)) < 0) {
+        fprintf(stderr, "Failed to open the runtime linker\n");
+        return 1;
+    }
+
+    if ((ld_text = mmap(NULL, 0x23000, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0)) == MAP_FAILED) {
+        fprintf(stderr, "Failed to map the runtime linker's .text\n");
+        return 1;
+    }
+
+    if ((ld_rodata = mmap(ld_text + 0x223000, 0x1000, PROT_READ, MAP_PRIVATE, fd, 0x23000)) == MAP_FAILED) {
+        fprintf(stderr, "Failed to map the runtime linker's .rodata\n");
+        return 1;
+    }
+
+    if ((ld_data = mmap(ld_text + 0x224000, 0x1000, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0x24000)) == MAP_FAILED) {
+        fprintf(stderr, "Failed to map the runtime linker .data\n");
+        return 1;
+    }
+
+    printf("Mapping successful!\n");
+    printf("You can check procfs maps to see actual permissions.\n");
+    printf("%s .text:   %p\n", LD_LINUX_PATH, ld_text);
+    printf("%s .rodata: %p\n", LD_LINUX_PATH, ld_rodata);
+    printf("%s .data:   %p\n", LD_LINUX_PATH, ld_data);
+
+    printf("Press any key to continue...\n");
+    read(0, &buf, 1);
+
+    munmap(ld_data, 0x23000);
+    munmap(ld_rodata, 0x1000);
+    munmap(ld_text, 0x1000);
+    close(fd);
+
+    return 0;
+}