Correct the maximum output size in cipher_test.cc

EVP_CIPH_NO_PADDING is a no-op when block_size is one, yet we sized the
output expecting it to always add a byte of padding. (I don't think this
makes a difference because most call sites of DoCipher set
EVP_CIPH_NO_PADDING.)

Bug: 494
Change-Id: Ic75e48a60e669270a093416b862ec03706e1d6ef
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/55386
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/cipher_extra/cipher_test.cc

diff --git a/crypto/cipher_extra/cipher_test.cc b/crypto/cipher_extra/cipher_test.cc
index 44c3570..1cbda56 100644
--- a/crypto/cipher_extra/cipher_test.cc
+++ b/crypto/cipher_extra/cipher_test.cc
@@ -126,9 +126,10 @@
                      bssl::Span<const uint8_t> in, size_t chunk,
                      bool in_place) {
   size_t max_out = in.size();
-  if ((EVP_CIPHER_CTX_flags(ctx) & EVP_CIPH_NO_PADDING) == 0 &&
+  size_t block_size = EVP_CIPHER_CTX_block_size(ctx);
+  if (block_size > 1 &&
+      (EVP_CIPHER_CTX_flags(ctx) & EVP_CIPH_NO_PADDING) == 0 &&
       EVP_CIPHER_CTX_encrypting(ctx)) {
-    unsigned block_size = EVP_CIPHER_CTX_block_size(ctx);
     max_out += block_size - (max_out % block_size);
   }
   out->resize(max_out);