# DP: libsanitzer: Remove crypt and crypt_r interceptors.

From 9b116160a1482c5c0c199f9c21d78a527d11d9ea Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Fri, 28 Apr 2023 09:59:17 -0700
Subject: [PATCH] Remove crypt and crypt_r interceptors

From Florian Weimer's D144073

> On GNU/Linux (glibc), the crypt and crypt_r functions are not part of the main shared object (libc.so.6), but libcrypt (with multiple possible sonames). The sanitizer libraries do not depend on libcrypt, so it can happen that during sanitizer library initialization, no real implementation will be found because the crypt, crypt_r functions are not present in the process image (yet). If its interceptors are called nevertheless, this results in a call through a null pointer when the sanitizer library attempts to forward the call to the real implementation.
>
> Many distributions have already switched to libxcrypt, a library that is separate from glibc and that can be build with sanitizers directly (avoiding the need for interceptors). This patch disables building the interceptor for glibc targets.

Let's remove crypt and crypt_r interceptors (D68431) to fix issues with
newer glibc.

For older glibc, msan will not know that an uninstrumented crypt_r call
initializes `data`, so there is a risk for false positives. However, with some
codebase survey, I think crypt_r uses are very few and the call sites typically
have a `memset(&data, 0, sizeof(data));` anyway.

Fix https://github.com/google/sanitizers/issues/1365
Related: https://bugzilla.redhat.com/show_bug.cgi?id=2169432

Reviewed By: #sanitizers, fweimer, thesamesam, vitalybuka

Differential Revision: https://reviews.llvm.org/D149403
---
 .../sanitizer_common_interceptors.inc         | 37 -------------------
 .../sanitizer_platform_interceptors.h         |  2 -
 .../sanitizer_platform_limits_posix.cpp       |  8 ----
 .../sanitizer_platform_limits_posix.h         |  1 -
 4 files changed, 48 deletions(-)

--- a/src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc
@@ -10187,41 +10187,6 @@ INTERCEPTOR(SSIZE_T, getrandom, void *bu
 #define INIT_GETRANDOM
 #endif
 
-#if SANITIZER_INTERCEPT_CRYPT
-INTERCEPTOR(char *, crypt, char *key, char *salt) {
-  void *ctx;
-  COMMON_INTERCEPTOR_ENTER(ctx, crypt, key, salt);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, key, internal_strlen(key) + 1);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, salt, internal_strlen(salt) + 1);
-  char *res = REAL(crypt)(key, salt);
-  if (res != nullptr)
-    COMMON_INTERCEPTOR_INITIALIZE_RANGE(res, internal_strlen(res) + 1);
-  return res;
-}
-#define INIT_CRYPT COMMON_INTERCEPT_FUNCTION(crypt);
-#else
-#define INIT_CRYPT
-#endif
-
-#if SANITIZER_INTERCEPT_CRYPT_R
-INTERCEPTOR(char *, crypt_r, char *key, char *salt, void *data) {
-  void *ctx;
-  COMMON_INTERCEPTOR_ENTER(ctx, crypt_r, key, salt, data);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, key, internal_strlen(key) + 1);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, salt, internal_strlen(salt) + 1);
-  char *res = REAL(crypt_r)(key, salt, data);
-  if (res != nullptr) {
-    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, data,
-                                   __sanitizer::struct_crypt_data_sz);
-    COMMON_INTERCEPTOR_INITIALIZE_RANGE(res, internal_strlen(res) + 1);
-  }
-  return res;
-}
-#define INIT_CRYPT_R COMMON_INTERCEPT_FUNCTION(crypt_r);
-#else
-#define INIT_CRYPT_R
-#endif
-
 #if SANITIZER_INTERCEPT_GETENTROPY
 INTERCEPTOR(int, getentropy, void *buf, SIZE_T buflen) {
   void *ctx;
@@ -10772,8 +10737,6 @@ static void InitializeCommonInterceptors
   INIT_GETUSERSHELL;
   INIT_SL_INIT;
   INIT_GETRANDOM;
-  INIT_CRYPT;
-  INIT_CRYPT_R;
   INIT_GETENTROPY;
   INIT_QSORT;
   INIT_QSORT_R;
--- a/src/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h
+++ b/src/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h
@@ -571,8 +571,6 @@
 #define SANITIZER_INTERCEPT_FDEVNAME SI_FREEBSD
 #define SANITIZER_INTERCEPT_GETUSERSHELL (SI_POSIX && !SI_ANDROID)
 #define SANITIZER_INTERCEPT_SL_INIT (SI_FREEBSD || SI_NETBSD)
-#define SANITIZER_INTERCEPT_CRYPT (SI_POSIX && !SI_ANDROID)
-#define SANITIZER_INTERCEPT_CRYPT_R (SI_LINUX && !SI_ANDROID)
 
 #define SANITIZER_INTERCEPT_GETRANDOM \
   ((SI_LINUX && __GLIBC_PREREQ(2, 25)) || SI_FREEBSD)
--- a/src/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cpp
+++ b/src/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cpp
@@ -177,10 +177,6 @@ typedef struct user_fpregs elf_fpregset_
 #  include "sanitizer_platform_interceptors.h"
 #  include "sanitizer_platform_limits_posix.h"
 
-#if SANITIZER_INTERCEPT_CRYPT_R
-#include <crypt.h>
-#endif
-
 namespace __sanitizer {
   unsigned struct_utsname_sz = sizeof(struct utsname);
   unsigned struct_stat_sz = sizeof(struct stat);
@@ -284,10 +280,6 @@ namespace __sanitizer {
   unsigned struct_statvfs64_sz = sizeof(struct statvfs64);
 #endif // SANITIZER_LINUX && !SANITIZER_ANDROID
 
-#if SANITIZER_INTERCEPT_CRYPT_R
-  unsigned struct_crypt_data_sz = sizeof(struct crypt_data);
-#endif
-
 #if SANITIZER_LINUX && !SANITIZER_ANDROID
   unsigned struct_timex_sz = sizeof(struct timex);
   unsigned struct_msqid_ds_sz = sizeof(struct msqid_ds);
--- a/src/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
+++ b/src/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -319,7 +319,6 @@ extern unsigned struct_msqid_ds_sz;
 extern unsigned struct_mq_attr_sz;
 extern unsigned struct_timex_sz;
 extern unsigned struct_statvfs_sz;
-extern unsigned struct_crypt_data_sz;
 #endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
 
 struct __sanitizer_iovec {
