Add a function to query output length of symmetric cipher

4 files changed, 18 insertions, 1 deletions

diff --git a/src/lib/ffi/ffi.h b/src/lib/ffi/ffi.h
index 19a65f946..89ac30e27 100644
--- a/src/lib/ffi/ffi.h
+++ b/src/lib/ffi/ffi.h
@@ -416,6 +416,8 @@ BOTAN_PUBLIC_API(2,0) int botan_cipher_init(botan_cipher_t* cipher, const char*
 
 BOTAN_PUBLIC_API(2,8) int botan_cipher_name(botan_cipher_t cipher, char* name, size_t* name_len);
 
+BOTAN_PUBLIC_API(2,8) int botan_cipher_output_length(botan_cipher_t cipher, size_t in_len, size_t* out_len);
+
 BOTAN_PUBLIC_API(2,0) int botan_cipher_valid_nonce_length(botan_cipher_t cipher, size_t nl);
 BOTAN_PUBLIC_API(2,0) int botan_cipher_get_tag_length(botan_cipher_t cipher, size_t* tag_size);
 BOTAN_PUBLIC_API(2,0) int botan_cipher_get_default_nonce_length(botan_cipher_t cipher, size_t* nl);
diff --git a/src/lib/ffi/ffi_cipher.cpp b/src/lib/ffi/ffi_cipher.cpp
index 094656fd2..8dee35a81 100644
--- a/src/lib/ffi/ffi_cipher.cpp
+++ b/src/lib/ffi/ffi_cipher.cpp
@@ -41,6 +41,14 @@ int botan_cipher_clear(botan_cipher_t cipher)
    return BOTAN_FFI_DO(Botan::Cipher_Mode, cipher, c, { c.clear(); });
    }
 
+int botan_cipher_output_length(botan_cipher_t cipher, size_t in_len, size_t* out_len)
+   {
+   if(out_len == nullptr)
+      return BOTAN_FFI_ERROR_NULL_POINTER;
+
+   return BOTAN_FFI_DO(Botan::Cipher_Mode, cipher, c, { *out_len = c.output_length(in_len); });
+   }
+
 int botan_cipher_query_keylen(botan_cipher_t cipher,
                               size_t* out_minimum_keylength,
                               size_t* out_maximum_keylength)
diff --git a/src/lib/ffi/ffi_pk_op.cpp b/src/lib/ffi/ffi_pk_op.cpp
index 0f18fca3e..5f2437a10 100644
--- a/src/lib/ffi/ffi_pk_op.cpp
+++ b/src/lib/ffi/ffi_pk_op.cpp
@@ -46,6 +46,8 @@ int botan_pk_op_encrypt_destroy(botan_pk_op_encrypt_t op)
 
 int botan_pk_op_encrypt_output_length(botan_pk_op_encrypt_t op, size_t ptext_len, size_t* ctext_len)
    {
+   if(ctext_len == nullptr)
+      return BOTAN_FFI_ERROR_NULL_POINTER;
    return BOTAN_FFI_DO(Botan::PK_Encryptor, op, o, { *ctext_len = o.ciphertext_length(ptext_len); });
    }
 
@@ -88,6 +90,8 @@ int botan_pk_op_decrypt_destroy(botan_pk_op_decrypt_t op)
 
 int botan_pk_op_decrypt_output_length(botan_pk_op_decrypt_t op, size_t ctext_len, size_t* ptext_len)
    {
+   if(ptext_len == nullptr)
+      return BOTAN_FFI_ERROR_NULL_POINTER;
    return BOTAN_FFI_DO(Botan::PK_Decryptor, op, o, { *ptext_len = o.plaintext_length(ctext_len); });
    }
 
diff --git a/src/lib/ffi/ffi_util.h b/src/lib/ffi/ffi_util.h
index afd359dbb..2aa0edd83 100644
--- a/src/lib/ffi/ffi_util.h
+++ b/src/lib/ffi/ffi_util.h
@@ -136,10 +136,13 @@ int ffi_delete_object(botan_struct<T, M>* obj, const char* func_name)
 
 inline int write_output(uint8_t out[], size_t* out_len, const uint8_t buf[], size_t buf_len)
    {
+   if(out_len == nullptr)
+      return BOTAN_FFI_ERROR_NULL_POINTER;
+
    const size_t avail = *out_len;
    *out_len = buf_len;
 
-   if(avail >= buf_len)
+   if((avail >= buf_len) && (out != nullptr))
       {
       Botan::copy_mem(out, buf, buf_len);
       return BOTAN_FFI_SUCCESS;