fix(public-key): enforce message length validation for ECDSA signatures

src/PrivateKey.cpp

@@ -256,10 +256,9 @@ PublicKey PrivateKey::getPublicKey(TWPublicKeyType type) const {
 }
 
 int ecdsa_sign_digest_checked(const ecdsa_curve* curve, const uint8_t* priv_key, const uint8_t* digest, size_t digest_size, uint8_t* sig, uint8_t* pby, int (*is_canonical)(uint8_t by, uint8_t sig[64])) {
-    if (digest_size < 32) {
+    if (digest_size != 32) {
         return -1;
     }
-    assert(digest_size >= 32);
     return ecdsa_sign_digest(curve, priv_key, digest, sig, pby, is_canonical);
 }
 

src/PublicKey.cpp

@@ -20,7 +20,7 @@
 
 namespace TW {
 
-bool validateSignatureLength(TWPublicKeyType type, const Data& signature) {
+static bool validateSignatureLength(TWPublicKeyType type, const Data& signature) {
     switch (type) {
     case TWPublicKeyTypeSECP256k1:
     case TWPublicKeyTypeSECP256k1Extended:
@@ -35,6 +35,25 @@ bool validateSignatureLength(TWPublicKeyType type, const Data& signature) {
     }
 }
 
+static bool validateMessageLength(TWPublicKeyType type, const Data& message) {
+    switch (type) {
+    case TWPublicKeyTypeED25519:
+    case TWPublicKeyTypeCURVE25519:
+    case TWPublicKeyTypeED25519Blake2b:
+    case TWPublicKeyTypeED25519Cardano:
+        // Technically, we should allow any message size for ed25519.
+        return true;
+    case TWPublicKeyTypeSECP256k1:
+    case TWPublicKeyTypeNIST256p1:
+    case TWPublicKeyTypeSECP256k1Extended:
+    case TWPublicKeyTypeNIST256p1Extended:
+    case TWPublicKeyTypeStarkex:
+        return message.size() == PublicKey::ecdsaMessageSize;
+    default:
+        return false;
+    }
+}
+
 /// Determines if a collection of bytes makes a valid public key of the
 /// given type.
 bool PublicKey::isValid(const Data& data, enum TWPublicKeyType type) {
@@ -165,6 +184,9 @@ bool PublicKey::verify(const Data& signature, const Data& message) const {
     if (!validateSignatureLength(type, signature)) {
         return false;
     }
+    if (!validateMessageLength(type, message)) {
+        return false;
+    }
 
     switch (type) {
     case TWPublicKeyTypeSECP256k1:

src/PublicKey.h

@@ -37,9 +37,12 @@ class PublicKey {
     /// The number of bytes in a secp256k1 signature.
     static const size_t secp256k1SignatureSize = 65;
 
-    /// Magic number used in V compnent encoding
+    /// Magic number used in V component encoding
     static const byte SignatureVOffset = 27;
 
+    /// The exact number of bytes in a message that can be signed or verified.
+    static const size_t ecdsaMessageSize = 32;
+
     /// The public key bytes.
     Data bytes;