Merge pull request #3123 from SparkiDev/mp_rshb

rshb check range of n

wolfcrypt/src/integer.c

@@ -549,6 +549,17 @@ void mp_rshb (mp_int *c, int x)
     mp_digit r, rr;
     mp_digit D = x;
 
+    /* shifting by a negative number not supported */
+    if (x < 0) return;
+
+    /* shift digits first if needed */
+    if (x >= DIGIT_BIT) {
+        mp_rshd(c, x / DIGIT_BIT);
+        /* recalculate number of bits to shift */
+        D = x % DIGIT_BIT;
+    }
+
+    /* zero shifted is always zero */
     if (mp_iszero(c)) return;
 
     /* mask */

wolfcrypt/src/sp_int.c

@@ -658,21 +658,28 @@ int sp_sub(sp_int* a, sp_int* b, sp_int* r)
  */
 void sp_rshb(sp_int* a, int n, sp_int* r)
 {
-    int i;
+    int i = n / SP_WORD_SIZE;
     int j;
-    int s = n % SP_WORD_SIZE;
 
-    if (s == 0) {
+    if (i >= a->used) {
-        for (i = n / SP_WORD_SIZE, j = 0; i < a->used-1; i++, j++)
+       r->dp[0] = 0;
-            r->dp[j] = a->dp[i];
+       r->used = 0;
     }
     else {
-        for (i = n / SP_WORD_SIZE, j = 0; i < a->used-1; i++, j++)
+        n %= SP_WORD_SIZE;
-            r->dp[j] = (a->dp[i] >> s) | (a->dp[i+1] << (SP_WORD_SIZE - s));
+        if (n == 0) {
+            for (j = 0; i < a->used; i++, j++)
+                r->dp[j] = a->dp[i];
+            r->used = j;
         }
-    r->dp[j] = a->dp[i] >> s;
+        if (n > 0) {
+            for (j = 0; i < a->used-1; i++, j++)
+                r->dp[j] = (a->dp[i] >> n) | (a->dp[i+1] << (SP_WORD_SIZE - n));
+            r->dp[j] = a->dp[i] >> n;
             r->used = j + 1;
             sp_clamp(r);
+        }
+    }
 }
 
 /* Multiply a by digit n and put result into r shifting up o digits.

wolfcrypt/src/tfm.c

@@ -3415,6 +3415,17 @@ void fp_rshb(fp_int *c, int x)
     fp_digit r, rr;
     fp_digit D = x;
 
+    /* shifting by a negative number not supported */
+    if (x < 0) return;
+
+    /* shift digits first if needed */
+    if (x >= DIGIT_BIT) {
+        fp_rshd(c, x / DIGIT_BIT);
+        /* recalculate number of bits to shift */
+        D = x % DIGIT_BIT;
+    }
+
+    /* zero shifted is always zero */
     if (fp_iszero(c)) return;
 
     /* mask */