Use 0 not -1 (since type is size_t) for finalisation argument to do_cipher:

the NULL value for the input buffer is sufficient to notice this case.

CHANGES

@@ -11,7 +11,7 @@
      do_cipher is subtly changed if this flag is set: the return value
      is the number of characters written to the output buffer (zero is
      no longer an error code) or a negative error code. Also if the
-     input buffer is NULL and length -1 finalisation should be performed.
+     input buffer is NULL and length 0 finalisation should be performed.
      [Steve Henson]
 
   *) If a candidate issuer certificate is already part of the constructed

crypto/evp/evp_enc.c

@@ -368,10 +368,10 @@ int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
 
 	if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER)
 		{
-		i = ctx->cipher->do_cipher(ctx, out, NULL, -1);
+		i = ctx->cipher->do_cipher(ctx, out, NULL, 0);
 		if (i < 0)
 			return 0;
-		else
+		else 
 			*outl = i;
 		return 1;
 		}
@@ -483,7 +483,7 @@ int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
 
 	if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER)
 		{
-		i = ctx->cipher->do_cipher(ctx, out, NULL, -1);
+		i = ctx->cipher->do_cipher(ctx, out, NULL, 0);
 		if (i < 0)
 			return 0;
 		else