1 files changed, 51 insertions, 21 deletions
diff --git a/src/key.cpp b/src/key.cpp
index b57b7c506c..2199996cf3 100644
--- a/src/key.cpp
+++ b/src/key.cpp
@@ -332,30 +332,60 @@ public:
     }
 };
 
+int CompareBigEndian(const unsigned char *c1, size_t c1len, const unsigned char *c2, size_t c2len) {
+    while (c1len > c2len) {
+        if (*c1)
+            return 1;
+        c1++;
+        c1len--;
+    }
+    while (c2len > c1len) {
+        if (*c2)
+            return -1;
+        c2++;
+        c2len--;
+    }
+    while (c1len > 0) {
+        if (*c1 > *c2)
+            return 1;
+        if (*c2 > *c1)
+            return -1;
+        c1++;
+        c2++;
+        c1len--;
+    }
+    return 0;
+}
+
+// Order of secp256k1's generator minus 1.
+const unsigned char vchMaxModOrder[32] = {
+    0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+    0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
+    0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
+    0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
+};
+
+// Half of the order of secp256k1's generator minus 1.
+const unsigned char vchMaxModHalfOrder[32] = {
+    0x7F,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+    0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+    0x5D,0x57,0x6E,0x73,0x57,0xA4,0x50,0x1D,
+    0xDF,0xE9,0x2F,0x46,0x68,0x1B,0x20,0xA0
+};
+
+const unsigned char vchZero[0] = {};
+
+
 }; // end of anonymous namespace
 
 bool CKey::Check(const unsigned char *vch) {
-    // Do not convert to OpenSSL's data structures for range-checking keys,
-    // it's easy enough to do directly.
-    static const unsigned char vchMax[32] = {
-        0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
-        0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
-        0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
-        0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
-    };
-    bool fIsZero = true;
-    for (int i=0; i<32 && fIsZero; i++)
-        if (vch[i] != 0)
-            fIsZero = false;
-    if (fIsZero)
-        return false;
-    for (int i=0; i<32; i++) {
-        if (vch[i] < vchMax[i])
-            return true;
-        if (vch[i] > vchMax[i])
-            return false;
-    }
-    return true;
+    return CompareBigEndian(vch, 32, vchZero, 0) > 0 &&
+           CompareBigEndian(vch, 32, vchMaxModOrder, 32) <= 0;
+}
+
+bool CKey::CheckSignatureElement(const unsigned char *vch, int len, bool half) {
+    return CompareBigEndian(vch, len, vchZero, 0) > 0 &&
+           CompareBigEndian(vch, len, half ? vchMaxModHalfOrder : vchMaxModOrder, 32) <= 0;
 }
 
 void CKey::MakeNewKey(bool fCompressedIn) {