[dice] Move format_condig_descriptor to diced_open_dice

Test: atest diced_utils_test diced_sample_inputs_test \
diced_test diced_vendor_test diced_open_dice_cbor_test \
diced_client_test
Test: m pvmfw_img microdroid_manager
Test: atest microdroid_manager_test vmbase_example.integration_test
Bug: 267575445

Change-Id: Iba7f775c1d1a3070c119da546edad38c2bbf67ac
diff --git a/diced/open_dice/Android.bp b/diced/open_dice/Android.bp
index f4c2155..e581085 100644
--- a/diced/open_dice/Android.bp
+++ b/diced/open_dice/Android.bp
@@ -20,6 +20,7 @@
     name: "libdiced_open_dice_nostd",
     defaults: ["libdiced_open_dice_defaults"],
     rustlibs: [
+        "libopen_dice_bcc_bindgen_nostd",
         "libopen_dice_cbor_bindgen_nostd",
     ],
 }
@@ -28,6 +29,7 @@
     name: "libdiced_open_dice",
     defaults: ["libdiced_open_dice_defaults"],
     rustlibs: [
+        "libopen_dice_bcc_bindgen",
         "libopen_dice_cbor_bindgen",
         // For ZVec
         "libkeystore2_crypto_rust",
@@ -35,4 +37,7 @@
     features: [
         "std",
     ],
+    whole_static_libs: [
+        "libopen_dice_bcc",
+    ],
 }
\ No newline at end of file
diff --git a/diced/open_dice/src/bcc.rs b/diced/open_dice/src/bcc.rs
new file mode 100644
index 0000000..8bda225
--- /dev/null
+++ b/diced/open_dice/src/bcc.rs
@@ -0,0 +1,56 @@
+// Copyright 2023, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! This module mirrors the content in open-dice/include/dice/android/bcc.h
+
+use crate::error::{check_result, Result};
+use open_dice_bcc_bindgen::{
+    BccConfigValues, BccFormatConfigDescriptor, BCC_INPUT_COMPONENT_NAME,
+    BCC_INPUT_COMPONENT_VERSION, BCC_INPUT_RESETTABLE,
+};
+use std::{ffi::CStr, ptr};
+
+/// Formats a configuration descriptor following the BCC's specification.
+/// See https://cs.android.com/android/platform/superproject/+/master:hardware/interfaces/security/rkp/aidl/android/hardware/security/keymint/ProtectedData.aidl
+pub fn bcc_format_config_descriptor(
+    name: Option<&CStr>,
+    version: Option<u64>,
+    resettable: bool,
+    buffer: &mut [u8],
+) -> Result<usize> {
+    let mut inputs = 0;
+    if name.is_some() {
+        inputs |= BCC_INPUT_COMPONENT_NAME;
+    }
+    if version.is_some() {
+        inputs |= BCC_INPUT_COMPONENT_VERSION;
+    }
+    if resettable {
+        inputs |= BCC_INPUT_RESETTABLE;
+    }
+
+    let values = BccConfigValues {
+        inputs,
+        component_name: name.map_or(ptr::null(), |p| p.as_ptr()),
+        component_version: version.unwrap_or(0),
+    };
+
+    let mut buffer_size = 0;
+    // SAFETY: The function writes to the buffer, within the given bounds, and only reads the
+    // input values. It writes its result to buffer_size.
+    check_result(unsafe {
+        BccFormatConfigDescriptor(&values, buffer.len(), buffer.as_mut_ptr(), &mut buffer_size)
+    })?;
+    Ok(buffer_size)
+}
diff --git a/diced/open_dice/src/dice.rs b/diced/open_dice/src/dice.rs
index 93d9617..a4615d3 100644
--- a/diced/open_dice/src/dice.rs
+++ b/diced/open_dice/src/dice.rs
@@ -15,8 +15,9 @@
 //! Structs and functions about the types used in DICE.
 //! This module mirrors the content in open-dice/include/dice/dice.h
 
+pub use open_dice_cbor_bindgen::DiceMode;
 use open_dice_cbor_bindgen::{
-    DiceConfigType, DiceInputValues, DiceMode, DICE_CDI_SIZE, DICE_HASH_SIZE, DICE_HIDDEN_SIZE,
+    DiceConfigType, DiceInputValues, DICE_CDI_SIZE, DICE_HASH_SIZE, DICE_HIDDEN_SIZE,
     DICE_INLINE_CONFIG_SIZE,
 };
 use std::ptr;
diff --git a/diced/open_dice/src/error.rs b/diced/open_dice/src/error.rs
index 9cf2ae8..7405c51 100644
--- a/diced/open_dice/src/error.rs
+++ b/diced/open_dice/src/error.rs
@@ -29,11 +29,6 @@
     BufferTooSmall,
     /// Platform error.
     PlatformError,
-    /// Input string has an interior nul byte.
-    /// TODO(b/267575445): Remove this error once we change the param of
-    /// `format_config_descriptor to take &CStr.
-    #[cfg(feature = "std")]
-    CStrNulError,
     /// The allocation of a ZVec failed.
     #[cfg(feature = "std")]
     ZVecError(keystore2_crypto::zvec::Error),
@@ -57,8 +52,6 @@
             Self::BufferTooSmall => write!(f, "buffer too small"),
             Self::PlatformError => write!(f, "platform error"),
             #[cfg(feature = "std")]
-            Self::CStrNulError => write!(f, "input string has an interior nul byte"),
-            #[cfg(feature = "std")]
             Self::ZVecError(e) => write!(f, "ZVec allocation failed {e}"),
         }
     }
diff --git a/diced/open_dice/src/lib.rs b/diced/open_dice/src/lib.rs
index 4cdd5c9..0723b2d 100644
--- a/diced/open_dice/src/lib.rs
+++ b/diced/open_dice/src/lib.rs
@@ -20,10 +20,17 @@
 #[cfg(not(feature = "std"))]
 extern crate core as std;
 
+mod bcc;
 mod dice;
 mod error;
+#[cfg(feature = "std")]
+mod retry;
 
+pub use bcc::bcc_format_config_descriptor;
 pub use dice::{
-    Cdi, Config, Hash, Hidden, InlineConfig, InputValues, CDI_SIZE, HASH_SIZE, HIDDEN_SIZE,
+    Cdi, Config, DiceMode, Hash, Hidden, InlineConfig, InputValues, CDI_SIZE, HASH_SIZE,
+    HIDDEN_SIZE,
 };
 pub use error::{check_result, DiceError, Result};
+#[cfg(feature = "std")]
+pub use retry::retry_bcc_format_config_descriptor;
diff --git a/diced/open_dice/src/retry.rs b/diced/open_dice/src/retry.rs
new file mode 100644
index 0000000..648fd91
--- /dev/null
+++ b/diced/open_dice/src/retry.rs
@@ -0,0 +1,64 @@
+// Copyright 2023, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! This module implements a retry version for multiple DICE functions that
+//! require preallocated output buffer. As the retry functions require
+//! memory allocation on heap, currently we only expose these functions in
+//! std environment.
+
+use crate::bcc::bcc_format_config_descriptor;
+use crate::error::{DiceError, Result};
+use std::ffi::CStr;
+
+/// Retries the given function with bigger output buffer size.
+fn retry_with_bigger_buffer<F>(mut f: F) -> Result<Vec<u8>>
+where
+    F: FnMut(&mut Vec<u8>) -> Result<usize>,
+{
+    const INITIAL_BUFFER_SIZE: usize = 256;
+    const MAX_BUFFER_SIZE: usize = 64 * 1024 * 1024;
+
+    let mut buffer = vec![0u8; INITIAL_BUFFER_SIZE];
+    while buffer.len() <= MAX_BUFFER_SIZE {
+        match f(&mut buffer) {
+            Err(DiceError::BufferTooSmall) => {
+                let new_size = buffer.len() * 2;
+                buffer.resize(new_size, 0);
+            }
+            Err(e) => return Err(e),
+            Ok(actual_size) => {
+                if actual_size > buffer.len() {
+                    panic!(
+                        "actual_size larger than buffer size: open-dice function
+                         may have written past the end of the buffer."
+                    );
+                }
+                buffer.truncate(actual_size);
+                return Ok(buffer);
+            }
+        }
+    }
+    Err(DiceError::PlatformError)
+}
+
+/// Formats a configuration descriptor following the BCC's specification.
+pub fn retry_bcc_format_config_descriptor(
+    name: Option<&CStr>,
+    version: Option<u64>,
+    resettable: bool,
+) -> Result<Vec<u8>> {
+    retry_with_bigger_buffer(|buffer| {
+        bcc_format_config_descriptor(name, version, resettable, buffer)
+    })
+}