math: change get_digit() return value

unsigned long is 32bit wide when compiling with the compiler flag "-mx32"
but the digit size of the math libraries is still 64 bit which lead to
the buggy ecc code.

Therefore define a new type ltc_mp_digit with the correct width and use
that as return value of get_digit()

Has been tested with all three math providers

src/headers/tomcrypt_cfg.h

@@ -122,6 +122,11 @@ typedef ulong32 __attribute__((__may_alias__)) LTC_FAST_TYPE;
   #endif
 #endif
 
+#ifdef ENDIAN_64BITWORD
+typedef ulong64 ltc_mp_digit;
+#else
+typedef ulong32 ltc_mp_digit;
+#endif
 
 #ifdef LTC_NO_FAST
    #ifdef LTC_FAST

src/headers/tomcrypt_math.h

@@ -80,7 +80,7 @@ typedef struct {
      @param n  The number of the digit to fetch
      @return  The bits_per_digit  sized n'th digit of a
    */
-   unsigned long (*get_digit)(void *a, int n);
+   ltc_mp_digit (*get_digit)(void *a, int n);
 
    /** Get the number of digits that represent the number
      @param a   The number to count

src/math/gmp_desc.c

@@ -74,7 +74,7 @@ static unsigned long get_int(void *a)
    return mpz_get_ui(a);
 }
 
-static unsigned long get_digit(void *a, int n)
+static ltc_mp_digit get_digit(void *a, int n)
 {
    LTC_ARGCHK(a != NULL);
    return mpz_getlimbn(a, n);

src/math/ltm_desc.c

@@ -100,7 +100,7 @@ static unsigned long get_int(void *a)
    return mp_get_int(a);
 }
 
-static unsigned long get_digit(void *a, int n)
+static ltc_mp_digit get_digit(void *a, int n)
 {
    mp_int *A;
    LTC_ARGCHK(a != NULL);

src/math/tfm_desc.c

@@ -99,7 +99,7 @@ static unsigned long get_int(void *a)
    return A->used > 0 ? A->dp[0] : 0;
 }
 
-static unsigned long get_digit(void *a, int n)
+static ltc_mp_digit get_digit(void *a, int n)
 {
    fp_int *A;
    LTC_ARGCHK(a != NULL);

src/pk/ecc/ltc_ecc_mulmod.c

@@ -41,7 +41,7 @@ int ltc_ecc_mulmod(void *k, ecc_point *G, ecc_point *R, void *modulus, int map)
    ecc_point *tG, *M[8];
    int        i, j, err;
    void       *mu, *mp;
-   unsigned long buf;
+   ltc_mp_digit buf;
    int        first, bitbuf, bitcpy, bitcnt, mode, digidx;
 
    LTC_ARGCHK(k       != NULL);

src/pk/ecc/ltc_ecc_mulmod_timing.c

@@ -39,7 +39,7 @@ int ltc_ecc_mulmod(void *k, ecc_point *G, ecc_point *R, void *modulus, int map)
    ecc_point *tG, *M[3];
    int        i, j, err;
    void       *mu, *mp;
-   unsigned long buf;
+   ltc_mp_digit buf;
    int        bitcnt, mode, digidx;
 
    LTC_ARGCHK(k       != NULL);