modules: make use of secure memory erasure

Use empty initialization of structs to minimize the memset() usage, to
reduce the amount of calls which are not sensitive.

Non trivial changes:

- pam_env:
  * erase environment variables where possible

- pam_exec:
  * erase responce on error
  * erase auth token

- pam_pwhistory:
  * erase buffers containing old passwords

- pam_selinux: skip overwriting data structure consisting of only
  pointers to insensitive data, which also gets free'd afterwards (so
  it currently does not protect against double-free or use-after-free on
  the member pointers)

- pam_unix: erase cipher data in more places

- pam_userdb: erase password hashes

1 files changed, 3 insertions, 1 deletions

diff --git a/modules/pam_namespace/md5.c b/modules/pam_namespace/md5.c
index 22e41ee0..07ad9a02 100644
--- a/modules/pam_namespace/md5.c
+++ b/modules/pam_namespace/md5.c
@@ -21,6 +21,8 @@
 #include "md5.h"
 #include <string.h>
 
+#include "pam_inline.h"
+
 #define MD5Name(x) x
 
 #ifdef WORDS_BIGENDIAN
@@ -149,7 +151,7 @@ void MD5Name(MD5Final)(unsigned char digest[16], struct MD5Context *ctx)
 	MD5Name(MD5Transform)(ctx->buf.i, ctx->in.i);
 	byteReverse(ctx->buf.c, 4);
 	memcpy(digest, ctx->buf.c, 16);
-	memset(ctx, 0, sizeof(*ctx));	/* In case it's sensitive */
+	pam_overwrite_object(ctx);	/* In case it's sensitive */
 }
 
 /* The four core functions - F1 is optimized somewhat */