[avb][test] Move test util methods to a separate module

Bug: 256148034
Test: atest libpvmfw_avb.integration_test
Change-Id: Ibd24eadd1d8d8d6007dab9f63a28c963790a8563
diff --git a/pvmfw/avb/tests/utils.rs b/pvmfw/avb/tests/utils.rs
new file mode 100644
index 0000000..aa40bb8
--- /dev/null
+++ b/pvmfw/avb/tests/utils.rs
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 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.
+ */
+
+//! Utility methods used by API tests.
+
+use anyhow::Result;
+use avb_bindgen::{
+    avb_footer_validate_and_byteswap, avb_vbmeta_image_header_to_host_byte_order, AvbFooter,
+    AvbVBMetaImageHeader,
+};
+use pvmfw_avb::{verify_payload, AvbSlotVerifyError};
+use std::{
+    fs,
+    mem::{size_of, transmute, MaybeUninit},
+};
+
+const MICRODROID_KERNEL_IMG_PATH: &str = "microdroid_kernel";
+const INITRD_NORMAL_IMG_PATH: &str = "microdroid_initrd_normal.img";
+const INITRD_DEBUG_IMG_PATH: &str = "microdroid_initrd_debuggable.img";
+const PUBLIC_KEY_RSA4096_PATH: &str = "data/testkey_rsa4096_pub.bin";
+
+pub const PUBLIC_KEY_RSA2048_PATH: &str = "data/testkey_rsa2048_pub.bin";
+
+pub fn assert_payload_verification_with_initrd_eq(
+    kernel: &[u8],
+    initrd: &[u8],
+    trusted_public_key: &[u8],
+    expected_result: Result<(), AvbSlotVerifyError>,
+) -> Result<()> {
+    assert_payload_verification_eq(kernel, Some(initrd), trusted_public_key, expected_result)
+}
+
+pub fn assert_payload_verification_eq(
+    kernel: &[u8],
+    initrd: Option<&[u8]>,
+    trusted_public_key: &[u8],
+    expected_result: Result<(), AvbSlotVerifyError>,
+) -> Result<()> {
+    assert_eq!(expected_result, verify_payload(kernel, initrd, trusted_public_key));
+    Ok(())
+}
+
+pub fn load_latest_signed_kernel() -> Result<Vec<u8>> {
+    Ok(fs::read(MICRODROID_KERNEL_IMG_PATH)?)
+}
+
+pub fn load_latest_initrd_normal() -> Result<Vec<u8>> {
+    Ok(fs::read(INITRD_NORMAL_IMG_PATH)?)
+}
+
+pub fn load_latest_initrd_debug() -> Result<Vec<u8>> {
+    Ok(fs::read(INITRD_DEBUG_IMG_PATH)?)
+}
+
+pub fn load_trusted_public_key() -> Result<Vec<u8>> {
+    Ok(fs::read(PUBLIC_KEY_RSA4096_PATH)?)
+}
+
+pub fn extract_avb_footer(kernel: &[u8]) -> Result<AvbFooter> {
+    let footer_start = kernel.len() - size_of::<AvbFooter>();
+    // SAFETY: The slice is the same size as the struct which only contains simple data types.
+    let mut footer = unsafe {
+        transmute::<[u8; size_of::<AvbFooter>()], AvbFooter>(kernel[footer_start..].try_into()?)
+    };
+    // SAFETY: The function updates the struct in-place.
+    unsafe {
+        avb_footer_validate_and_byteswap(&footer, &mut footer);
+    }
+    Ok(footer)
+}
+
+pub fn extract_vbmeta_header(kernel: &[u8], footer: &AvbFooter) -> Result<AvbVBMetaImageHeader> {
+    let vbmeta_offset: usize = footer.vbmeta_offset.try_into()?;
+    let vbmeta_size: usize = footer.vbmeta_size.try_into()?;
+    let vbmeta_src = &kernel[vbmeta_offset..(vbmeta_offset + vbmeta_size)];
+    // SAFETY: The latest kernel has a valid VBMeta header at the position specified in footer.
+    let vbmeta_header = unsafe {
+        let mut header = MaybeUninit::uninit();
+        let src = vbmeta_src.as_ptr() as *const _ as *const AvbVBMetaImageHeader;
+        avb_vbmeta_image_header_to_host_byte_order(src, header.as_mut_ptr());
+        header.assume_init()
+    };
+    Ok(vbmeta_header)
+}