[refactoring] Group all the CBOR util functions in cbor_util

This cl only moves all the CBOR utility functions in one place.
Some return error types are adjusted to adapt the change. There
should be no behavior change.

Bug: 310931749
Test: atest rialto_test
Change-Id: Ie3db9c93b1355d25d7d796818e19e554560e1f23
diff --git a/service_vm/comm/Android.bp b/service_vm/comm/Android.bp
index bdfc099..bf923a4 100644
--- a/service_vm/comm/Android.bp
+++ b/service_vm/comm/Android.bp
@@ -23,6 +23,7 @@
     rustlibs: [
         "libbssl_avf_error_nostd",
         "libciborium_nostd",
+        "libcbor_util_nostd",
         "libcoset_nostd",
         "libder_nostd",
         "liblog_rust_nostd",
@@ -36,6 +37,7 @@
     rustlibs: [
         "libbssl_avf_error",
         "libciborium",
+        "libcbor_util",
         "libcoset",
         "liblog_rust",
         "libserde",
diff --git a/service_vm/comm/src/csr.rs b/service_vm/comm/src/csr.rs
index f14787f..a87d28f 100644
--- a/service_vm/comm/src/csr.rs
+++ b/service_vm/comm/src/csr.rs
@@ -17,9 +17,9 @@
 
 use alloc::vec;
 use alloc::vec::Vec;
+use cbor_util::{cbor_value_type, value_to_bytes};
 use ciborium::Value;
 use coset::{self, CborSerializable, CoseError};
-use log::error;
 
 /// Represents a CSR sent from the client VM to the service VM for attestation.
 ///
@@ -99,37 +99,3 @@
         })
     }
 }
-
-/// Converts the provided value `v` to bytes array.
-pub fn value_to_bytes(v: Value, context: &'static str) -> coset::Result<Vec<u8>> {
-    v.into_bytes().map_err(|e| to_unexpected_item_error(&e, "bstr", context))
-}
-
-/// Builds a `CoseError::UnexpectedItem` error when the provided value `v` is not of the expected
-/// type `expected_type` and logs the error message with the provided `context`.
-pub fn to_unexpected_item_error(
-    v: &Value,
-    expected_type: &'static str,
-    context: &'static str,
-) -> CoseError {
-    let v_type = cbor_value_type(v);
-    assert!(v_type != expected_type);
-    error!("The provided value type '{v_type}' is not of type '{expected_type}': {context}");
-    CoseError::UnexpectedItem(v_type, expected_type)
-}
-
-/// Reads the type of the provided value `v`.
-pub fn cbor_value_type(v: &Value) -> &'static str {
-    match v {
-        Value::Integer(_) => "int",
-        Value::Bytes(_) => "bstr",
-        Value::Float(_) => "float",
-        Value::Text(_) => "tstr",
-        Value::Bool(_) => "bool",
-        Value::Null => "nul",
-        Value::Tag(_, _) => "tag",
-        Value::Array(_) => "array",
-        Value::Map(_) => "map",
-        _ => "other",
-    }
-}
diff --git a/service_vm/comm/src/lib.rs b/service_vm/comm/src/lib.rs
index 343d48e..bb85a26 100644
--- a/service_vm/comm/src/lib.rs
+++ b/service_vm/comm/src/lib.rs
@@ -23,7 +23,7 @@
 mod message;
 mod vsock;
 
-pub use csr::{cbor_value_type, to_unexpected_item_error, value_to_bytes, Csr, CsrPayload};
+pub use csr::{Csr, CsrPayload};
 pub use message::{
     ClientVmAttestationParams, EcdsaP256KeyPair, GenerateCertificateRequestParams, Request,
     RequestProcessingError, Response, ServiceVmRequest,
diff --git a/service_vm/requests/src/dice.rs b/service_vm/requests/src/dice.rs
index 15cfbc9..557b678 100644
--- a/service_vm/requests/src/dice.rs
+++ b/service_vm/requests/src/dice.rs
@@ -16,7 +16,11 @@
 
 use alloc::string::String;
 use alloc::vec::Vec;
-use ciborium::value::{Integer, Value};
+use cbor_util::{
+    cbor_value_type, value_to_array, value_to_byte_array, value_to_bytes, value_to_map,
+    value_to_num, value_to_text,
+};
+use ciborium::value::Value;
 use core::cell::OnceCell;
 use core::result;
 use coset::{
@@ -24,9 +28,7 @@
 };
 use diced_open_dice::{DiceMode, HASH_SIZE};
 use log::error;
-use service_vm_comm::{
-    cbor_value_type, to_unexpected_item_error, value_to_bytes, RequestProcessingError,
-};
+use service_vm_comm::RequestProcessingError;
 
 type Result<T> = result::Result<T, RequestProcessingError>;
 
@@ -399,33 +401,6 @@
     }
 }
 
-fn value_to_array(v: Value, context: &'static str) -> coset::Result<Vec<Value>> {
-    v.into_array().map_err(|e| to_unexpected_item_error(&e, "array", context))
-}
-
-fn value_to_text(v: Value, context: &'static str) -> coset::Result<String> {
-    v.into_text().map_err(|e| to_unexpected_item_error(&e, "tstr", context))
-}
-
-fn value_to_map(v: Value, context: &'static str) -> coset::Result<Vec<(Value, Value)>> {
-    v.into_map().map_err(|e| to_unexpected_item_error(&e, "map", context))
-}
-
-fn value_to_num<T: TryFrom<Integer>>(v: Value, context: &'static str) -> Result<T> {
-    let num = v.into_integer().map_err(|e| to_unexpected_item_error(&e, "int", context))?;
-    num.try_into().map_err(|_| {
-        error!("The provided value '{num:?}' is not a valid number: {context}");
-        RequestProcessingError::InvalidDiceChain
-    })
-}
-
-fn value_to_byte_array<const N: usize>(v: Value, context: &'static str) -> Result<[u8; N]> {
-    value_to_bytes(v, context)?.try_into().map_err(|e| {
-        error!("The provided value '{context}' is not an array of length {N}: {e:?}");
-        RequestProcessingError::InternalError
-    })
-}
-
 fn to_mode(value: Value) -> Result<DiceMode> {
     let mode = match value {
         // Mode is supposed to be encoded as a 1-byte bstr, but some implementations instead