safevar.c

#include <stdio.h>
#include <stdlib.h>

#include "common/md5.h"

// __builtin_types_compatible_p

/////////////////////////////////////
// some preprocessor magic

// double indirection needed to concatenate two macro expansions
#define M_CONCAT(x, y) M_PASTER(x, y)
#define M_PASTER(x, y) x##y

/////////////////////////////////////
// hack to detect empty vararg
// based on a majestic hack found in
// http://gustedt.wordpress.com/2010/06/08/detect-empty-macro-arguments/
// kudos to Jens Gustedt.
#define _ARG16(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13,     \
               _14, _15, ...)                                                  \
  _15
#define HAS_COMMA(...)                                                         \
  _ARG16(__VA_ARGS__, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0)
#define _TRIGGER_PARENTHESIS_(...) ,
#define ISEMPTY(...)                                                           \
  _ISEMPTY(/* test if there is just one argument, eventually an empty          \
              one */                                                           \
           HAS_COMMA(__VA_ARGS__), /* test if _TRIGGER_PARENTHESIS_ together   \
                                      with the argument                        \
                                      adds a comma */                          \
           HAS_COMMA(_TRIGGER_PARENTHESIS_ __VA_ARGS__), /* test if the        \
                                                            argument together  \
                                                            with a parenthesis \
                                                            adds a comma */    \
           HAS_COMMA(__VA_ARGS__(/*empty*/)), /* test if placing it between    \
                                                 _TRIGGER_PARENTHESIS_ and the \
                                                 parenthesis adds a comma */   \
           HAS_COMMA(_TRIGGER_PARENTHESIS_ __VA_ARGS__(/*empty*/)))

#define _IS_EMPTY_CASE_0001 ,
#define PASTE5(_0, _1, _2, _3, _4) _0##_1##_2##_3##_4
#define _ISEMPTY(_0, _1, _2, _3)                                               \
  HAS_COMMA(PASTE5(_IS_EMPTY_CASE_, _0, _1, _2, _3))

////////// REAL CODE

#define _MD5_COND_1(iftrue, iffalse) iftrue
#define _MD5_COND_0(iftrue, iffalse) iffalse
#define _MD5_IF_LAST(iftrue, iffalse, eat, ...)                                \
  M_CONCAT(_MD5_COND_, ISEMPTY(__VA_ARGS__))(iftrue, iffalse)
#define _MD5_SENTINEL(...) NULL

#define _STATIC_ASSERT(COND, MSG)                                              \
  typedef char static_assertion_##MSG[2 * (!!(COND)) - 1]

#define _MD5_CHECK_LEN(len)                                                    \
  ({                                                                           \
    _STATIC_ASSERT(sizeof(typeof(len)) == sizeof(size_t),                      \
                   LENGTH_MUST_BE_SIZE_T);                                     \
    static_assertion_LENGTH_MUST_BE_SIZE_T dummy;                              \
    (void) dummy;                                                              \
    len;                                                                       \
  })

#define safe_md5_args_9(p, len, ...) ___BAD_ARGLIST_TOO_LONG

#define safe_md5_args_8(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_9, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_7(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_8, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_6(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_7, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_5(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_6, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_4(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_5, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_3(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_4, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_2(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_3, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args_1(p, len, ...)                                           \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_2, __VA_ARGS__)(__VA_ARGS__)
#define safe_md5_args(p, len, ...)                                             \
  p, _MD5_CHECK_LEN(len),                                                      \
      _MD5_IF_LAST(_MD5_SENTINEL, safe_md5_args_1, __VA_ARGS__)(__VA_ARGS__)
#define safe_cs_md5(ha1, ...) cs_md5(ha1, safe_md5_args(__VA_ARGS__))

static void add_pw_line(char ha1[33], const char *user, const char *domain,
                        const char *pass) {
  safe_cs_md5(ha1, user, strlen(user), ":", (size_t)1, domain, strlen(domain),
              ":", (size_t)1, pass, strlen(pass), NULL);
  printf("%s:%s:%s\n", user, domain, ha1);
}

int main() {
  char ha1[33];
  add_pw_line(ha1, "joe", "cesanta.com", "bloggs");

  return 0;
}