Realization while thinking about the recently added truncate: in a STL

container like vector, truncate is simply resize, but what
MemoryRegion called resize will zap the entire contents, and then what
was resize was called grow_to. This is really problematic in terms of
the goal of replacing MemoryRegion with a vector with a custom
allocator.

In this checkin:
  - Remove MemoryRegion::grow_to and MemoryRegion::truncate

  - Change the semantics of MemoryRegion::resize to change the size
    while keeping any current contents intact (up to the new size),
    zero initializing any new values.

Unrelated, just noticed the lack while I was in there, add a version
of CryptoBox::decrypt taking a std::string for the input.

2 files changed, 23 insertions, 5 deletions

diff --git a/src/constructs/cryptobox/cryptobox.cpp b/src/constructs/cryptobox/cryptobox.cpp
index 6dcca0754..61fe51a88 100644
--- a/src/constructs/cryptobox/cryptobox.cpp
+++ b/src/constructs/cryptobox/cryptobox.cpp
@@ -73,16 +73,18 @@ std::string encrypt(const byte input[], u32bit input_len,
       mac (20 bytes)
       ciphertext
    */
-   u32bit ciphertext_len = pipe.remaining(0);
+   const u32bit ciphertext_len = pipe.remaining(0);
 
-   SecureVector<byte> out_buf;
+   SecureVector<byte> out_buf(VERSION_CODE_LEN +
+                              PBKDF_SALT_LEN +
+                              MAC_OUTPUT_LEN +
+                              ciphertext_len);
 
    for(u32bit i = 0; i != VERSION_CODE_LEN; ++i)
-      out_buf.append(get_byte(i, CRYPTOBOX_VERSION_CODE));
+     out_buf[i] = get_byte(i, CRYPTOBOX_VERSION_CODE);
 
-   out_buf.append(pbkdf_salt.begin(), pbkdf_salt.size());
+   out_buf.copy(VERSION_CODE_LEN, pbkdf_salt, PBKDF_SALT_LEN);
 
-   out_buf.grow_to(out_buf.size() + MAC_OUTPUT_LEN + ciphertext_len);
    pipe.read(out_buf + VERSION_CODE_LEN + PBKDF_SALT_LEN, MAC_OUTPUT_LEN, 1);
    pipe.read(out_buf + VERSION_CODE_LEN + PBKDF_SALT_LEN + MAC_OUTPUT_LEN,
              ciphertext_len, 0);
@@ -140,6 +142,14 @@ std::string decrypt(const byte input[], u32bit input_len,
    return pipe.read_all_as_string(0);
    }
 
+std::string decrypt(const std::string& input,
+                    const std::string& passphrase)
+   {
+   return decrypt(reinterpret_cast<const byte*>(&input[0]),
+                  input.size(),
+                  passphrase);
+   }
+
 }
 
 }
diff --git a/src/constructs/cryptobox/cryptobox.h b/src/constructs/cryptobox/cryptobox.h
index 0380dcff9..12f054eff 100644
--- a/src/constructs/cryptobox/cryptobox.h
+++ b/src/constructs/cryptobox/cryptobox.h
@@ -38,6 +38,14 @@ BOTAN_DLL std::string encrypt(const byte input[], u32bit input_len,
 BOTAN_DLL std::string decrypt(const byte input[], u32bit input_len,
                               const std::string& passphrase);
 
+/**
+* Decrypt a message encrypted with CryptoBox::encrypt
+* @param input the input data
+* @param passphrase the passphrase used to encrypt the message
+*/
+BOTAN_DLL std::string decrypt(const std::string& input,
+                              const std::string& passphrase);
+
 }
 
 }