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Making LD_PRELOAD/LD_AUDIT modules with Python
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| .PHONY: all clean test | |
| PYTHON_CONFIG = python3-config | |
| CC = gcc -std=gnu11 | |
| CFLAGS = `$(PYTHON_CONFIG) --cflags` | |
| INCLUDES = `$(PYTHON_CONFIG) --includes` | |
| LIBS = `$(PYTHON_CONFIG) --libs` | |
| LD_PATH = `$(PYTHON_CONFIG) --prefix`/lib | |
| CYTHON_TARGETS = malloc | |
| TARGETS = preload | |
| SHARED_OBJS = $(addsuffix .so,$(TARGETS)) $(addsuffix .so,$(CYTHON_TARGETS)) | |
| all: $(SHARED_OBJS) | |
| #preload.so: preload.c | |
| #$(CC) -Wl,--export-dynamic -fPIC -shared -o $@ $^ -ldl | |
| %.so: %.c | |
| $(CC) $(CFLAGS) $(INCLUDES) -L$(LD_PATH) -Wl,--export-dynamic -fPIC -shared -o $@ $^ -ldl $(LIBS) | |
| %.c: %.pyx | |
| cython $^ | |
| prog: prog.c | |
| $(CC) -o $@ $^ -lm | |
| test: $(SHARED_OBJS) | |
| ./preload malloc ls | |
| clean: | |
| rm -f $(SHARED_OBJS) $(addsuffix .c,$(CYTHON_TARGETS)) $(addsuffix .h,$(CYTHON_TARGETS)) |
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| from libc.stdlib cimport malloc as libc_malloc | |
| cdef public void* malloc(size_t x): | |
| print('malloc({})'.format(x)) | |
| return libc_malloc(x) |
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| #/bin/sh | |
| PY_PRELOAD="$1" | |
| shift 1 | |
| env LD_AUDIT=./preload.so PY_PRELOAD="$PY_PRELOAD" $@ |
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| #include <stdio.h> | |
| #include <stdlib.h> | |
| #include <stdbool.h> | |
| #define __USE_GNU | |
| #define _GNU_SOURCE | |
| #include "Python.h" | |
| #include <link.h> | |
| #include <dlfcn.h> | |
| static void __attribute__ ((destructor)) fini(void) { | |
| Py_Finalize(); | |
| } | |
| static void __attribute__ ((constructor)) init(void) { | |
| Py_Initialize(); | |
| PyRun_SimpleStringFlags("from sys import path; from os import getcwd; path.insert(0, getcwd())", NULL); | |
| atexit(fini); | |
| } | |
| unsigned int la_version(unsigned int version) { | |
| return version; | |
| } | |
| uintptr_t la_symbind64(Elf64_Sym *sym, unsigned int ndx, uintptr_t *refcook, | |
| uintptr_t *defcook, unsigned int *flags, const char *symname) { | |
| if (0 == strcmp(symname, "malloc")) { | |
| const char *modname = getenv("PY_PRELOAD"); | |
| if (!modname) goto error; | |
| PyObject *mod = PyImport_ImportModule(modname); | |
| if (!mod) goto error; | |
| PyObject *modfile = PyObject_GetAttrString(mod, "__file__"); | |
| if (!modfile) goto error; | |
| char *filename = PyUnicode_AsUTF8(modfile); | |
| if (!filename) goto error; | |
| void* obj = dlopen(filename, RTLD_LAZY | RTLD_LOCAL); | |
| if (!obj) goto error; | |
| uintptr_t sym = (uintptr_t)dlsym(obj, symname); | |
| if (!sym) goto error; | |
| return (uintptr_t)sym; | |
| } | |
| error: | |
| return sym->st_value; | |
| } | |
| unsigned int la_objopen(struct link_map *map, Lmid_t lmid, uintptr_t *cookie) { | |
| return LA_FLG_BINDTO | LA_FLG_BINDFROM; | |
| } |
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| #include <stdio.h> | |
| #include <stdlib.h> | |
| int main(int argc, char *argv[]) { | |
| for (int i = 1; i < argc; ++i) { | |
| int arg = atoi(argv[i]); | |
| void *rv = malloc(arg); | |
| printf("%s(%d) -> %p\n", argv[0], arg, rv); | |
| } | |
| exit(EXIT_SUCCESS); | |
| return 0; | |
| } |
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