Allow building libfec without libavb

Add stub implementation for avb related functions to allow building
libfec without libavb support. This is useful to build the fec binary
when libavb isn't available on mac.

Test: build, unittests pass
Change-Id: I26f8de390c3c2c37bf48418fb31038ddd9863866

5 files changed, 260 insertions, 148 deletions

diff --git a/libfec/Android.bp b/libfec/Android.bp
index b355dfec..3da6fe7c 100644
--- a/libfec/Android.bp
+++ b/libfec/Android.bp
@@ -1,16 +1,22 @@
 // Copyright 2015 The Android Open Source Project
 
-cc_library {
-    name: "libfec",
-    host_supported: true,
-    recovery_available: true,
+cc_defaults {
+    name: "libfec_default",
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-O3",
+        "-D_LARGEFILE64_SOURCE",
+    ],
+
     srcs: [
         "fec_open.cpp",
         "fec_read.cpp",
         "fec_verity.cpp",
         "fec_process.cpp",
     ],
-    cflags: ["-Wall", "-Werror", "-O3", "-D_LARGEFILE64_SOURCE"],
+
     export_include_dirs: ["include"],
     // Exported header include/fec/io.h includes crypto_utils headers.
     export_shared_lib_headers: ["libcrypto_utils"],
@@ -25,13 +31,15 @@ cc_library {
     ],
 
     static_libs: [
-        "libavb",
         "libfec_rs",
     ],
 
     target: {
         host: {
-            cflags: ["-D_GNU_SOURCE", "-DFEC_NO_KLOG"]
+            cflags: [
+                "-D_GNU_SOURCE",
+                "-DFEC_NO_KLOG",
+            ],
         },
         linux_glibc: {
             sanitize: {
@@ -40,3 +48,28 @@ cc_library {
         },
     },
 }
+
+cc_library {
+    name: "libfec",
+    defaults: ["libfec_default"],
+    host_supported: true,
+    recovery_available: true,
+
+    target: {
+        linux: {
+            srcs: [
+                "avb_utils.cpp",
+            ],
+            static_libs: [
+                "libavb",
+            ],
+        },
+
+        // libavb isn't available on mac.
+        darwin: {
+            srcs: [
+                "avb_utils_stub.cpp",
+            ],
+        },
+    },
+}
diff --git a/libfec/avb_utils.cpp b/libfec/avb_utils.cpp
new file mode 100644
index 00000000..8913f2a1
--- /dev/null
+++ b/libfec/avb_utils.cpp
@@ -0,0 +1,160 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include "avb_utils.h"
+
+#include <android-base/strings.h>
+#include <libavb/libavb.h>
+
+#include "fec_private.h"
+
+int parse_vbmeta_from_footer(fec_handle *f, std::vector<uint8_t> *vbmeta) {
+    if (f->size <= AVB_FOOTER_SIZE) {
+        debug("file size not large enough to be avb images:" PRIu64, f->size);
+        return -1;
+    }
+
+    AvbFooter footer_read;
+    if (!raw_pread(f->fd, &footer_read, AVB_FOOTER_SIZE,
+                   f->size - AVB_FOOTER_SIZE)) {
+        error("failed to read footer: %s", strerror(errno));
+        return -1;
+    }
+
+    AvbFooter footer;
+    if (!avb_footer_validate_and_byteswap(&footer_read, &footer)) {
+        debug("invalid avb footer");
+        return -1;
+    }
+    uint64_t vbmeta_offset = footer.vbmeta_offset;
+    uint64_t vbmeta_size = footer.vbmeta_size;
+    check(vbmeta_offset <= f->size - sizeof(footer) - vbmeta_size);
+
+    std::vector<uint8_t> vbmeta_data(vbmeta_size, 0);
+    // TODO(xunchang) handle the sparse image with libsparse.
+    if (!raw_pread(f->fd, vbmeta_data.data(), vbmeta_data.size(),
+                   vbmeta_offset)) {
+        error("failed to read avb vbmeta: %s", strerror(errno));
+        return -1;
+    }
+
+    if (auto status = avb_vbmeta_image_verify(
+            vbmeta_data.data(), vbmeta_data.size(), nullptr, nullptr);
+        status != AVB_VBMETA_VERIFY_RESULT_OK &&
+        status != AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED) {
+        error("failed to verify avb vbmeta, status: %d", status);
+        return -1;
+    }
+    *vbmeta = std::move(vbmeta_data);
+    return 0;
+}
+
+int parse_avb_image(fec_handle *f, const std::vector<uint8_t> &vbmeta) {
+    // TODO(xunchang) check if avb verification or hashtree is disabled.
+
+    // Look for the hashtree descriptor, we expect exactly one descriptor in
+    // vbmeta.
+    // TODO(xunchang) handle the image with AvbHashDescriptor.
+    auto parse_descriptor = [](const AvbDescriptor *descriptor,
+                               void *user_data) {
+        if (descriptor &&
+            avb_be64toh(descriptor->tag) == AVB_DESCRIPTOR_TAG_HASHTREE) {
+            auto desp = static_cast<const AvbDescriptor **>(user_data);
+            *desp = descriptor;
+            return false;
+        }
+        return true;
+    };
+
+    const AvbHashtreeDescriptor *hashtree_descriptor_ptr = nullptr;
+    avb_descriptor_foreach(vbmeta.data(), vbmeta.size(), parse_descriptor,
+                           &hashtree_descriptor_ptr);
+
+    AvbHashtreeDescriptor hashtree_descriptor;
+    if (!avb_hashtree_descriptor_validate_and_byteswap(hashtree_descriptor_ptr,
+                                                       &hashtree_descriptor)) {
+        error("failed to verify avb hashtree descriptor");
+        return -1;
+    }
+
+    // The partition name, salt, root append right after the hashtree
+    // descriptor.
+    auto read_ptr = reinterpret_cast<const uint8_t *>(hashtree_descriptor_ptr);
+    // Calculate the offset with respect to the vbmeta; and check both the
+    // salt & root are within the range.
+    uint32_t salt_offset =
+        sizeof(AvbHashtreeDescriptor) + hashtree_descriptor.partition_name_len;
+    uint32_t root_offset = salt_offset + hashtree_descriptor.salt_len;
+    check(hashtree_descriptor.salt_len < vbmeta.size());
+    check(salt_offset < vbmeta.size() - hashtree_descriptor.salt_len);
+    check(hashtree_descriptor.root_digest_len < vbmeta.size());
+    check(root_offset < vbmeta.size() - hashtree_descriptor.root_digest_len);
+    std::vector<uint8_t> salt(
+        read_ptr + salt_offset,
+        read_ptr + salt_offset + hashtree_descriptor.salt_len);
+    std::vector<uint8_t> root_hash(
+        read_ptr + root_offset,
+        read_ptr + root_offset + hashtree_descriptor.root_digest_len);
+
+    // Expect the AVB image has the format:
+    // 1. hashtree
+    // 2. ecc data
+    // 3. vbmeta
+    // 4. avb footer
+    check(hashtree_descriptor.fec_offset ==
+          hashtree_descriptor.tree_offset + hashtree_descriptor.tree_size);
+    check(hashtree_descriptor.fec_offset <=
+          f->size - hashtree_descriptor.fec_size);
+
+    f->data_size = hashtree_descriptor.fec_offset;
+
+    f->ecc.blocks = fec_div_round_up(f->data_size, FEC_BLOCKSIZE);
+    f->ecc.rounds = fec_div_round_up(f->ecc.blocks, f->ecc.rsn);
+    f->ecc.size = hashtree_descriptor.fec_size;
+    f->ecc.start = hashtree_descriptor.fec_offset;
+    // TODO(xunchang) verify the integrity of the ecc data.
+    f->ecc.valid = true;
+
+    std::string hash_algorithm =
+        reinterpret_cast<char *>(hashtree_descriptor.hash_algorithm);
+    int nid = -1;
+    if (android::base::EqualsIgnoreCase(hash_algorithm, "sha1")) {
+        nid = NID_sha1;
+    } else if (android::base::EqualsIgnoreCase(hash_algorithm, "sha256")) {
+        nid = NID_sha256;
+    } else {
+        error("unsupported hash algorithm %s", hash_algorithm.c_str());
+    }
+
+    hashtree_info hashtree;
+    hashtree.initialize(hashtree_descriptor.tree_offset,
+                        hashtree_descriptor.tree_offset / FEC_BLOCKSIZE, salt,
+                        nid);
+    if (hashtree.verify_tree(f, root_hash.data()) != 0) {
+        error("failed to verify hashtree");
+        return -1;
+    }
+
+    // We have validate the hashtree,
+    f->data_size = hashtree.hash_start;
+    f->avb = {
+        .valid = true,
+        .vbmeta = vbmeta,
+        .hashtree = std::move(hashtree),
+    };
+
+    return 0;
+}
diff --git a/libfec/avb_utils.h b/libfec/avb_utils.h
new file mode 100644
index 00000000..78254508
--- /dev/null
+++ b/libfec/avb_utils.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <vector>
+
+struct fec_handle;
+
+// Checks if there is a valid AVB footer in the end of the image. If so, parses
+// the contents of vbmeta struct from the given AVB footer. Returns 0 on
+// success.
+int parse_vbmeta_from_footer(fec_handle *f, std::vector<uint8_t> *vbmeta);
+
+// Parses the AVB vbmeta for the information of hashtree and fec data.
+int parse_avb_image(fec_handle *f, const std::vector<uint8_t> &vbmeta);
diff --git a/libfec/avb_utils_stub.cpp b/libfec/avb_utils_stub.cpp
new file mode 100644
index 00000000..0b6061e5
--- /dev/null
+++ b/libfec/avb_utils_stub.cpp
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include "avb_utils.h"
+
+int parse_vbmeta_from_footer(fec_handle* /* f */,
+                             std::vector<uint8_t> * /* vbmeta */) {
+    return -1;
+}
+
+int parse_avb_image(fec_handle* /* f */,
+                    const std::vector<uint8_t>& /* vbmeta */) {
+    return -1;
+}
diff --git a/libfec/fec_open.cpp b/libfec/fec_open.cpp
index 8f3fa22d..fe458097 100644
--- a/libfec/fec_open.cpp
+++ b/libfec/fec_open.cpp
@@ -18,9 +18,7 @@
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 
-#include <android-base/strings.h>
 #include <ext4_utils/ext4_sb.h>
-#include <libavb/libavb.h>
 #include <squashfs_utils.h>
 
 #if defined(__linux__)
@@ -31,6 +29,7 @@
     #define fdatasync(fd) fcntl((fd), F_FULLFSYNC)
 #endif
 
+#include "avb_utils.h"
 #include "fec_private.h"
 
 /* used by `find_offset'; returns metadata size for a file size `size' and
@@ -495,145 +494,6 @@ int fec_get_status(struct fec_handle *f, struct fec_status *s)
     return 0;
 }
 
-static int parse_vbmeta_from_footer(fec_handle *f,
-                                    std::vector<uint8_t> *vbmeta) {
-    if (f->size <= AVB_FOOTER_SIZE) {
-        debug("file size not large enough to be avb images:" PRIu64, f->size);
-        return -1;
-    }
-
-    AvbFooter footer_read;
-    if (!raw_pread(f->fd, &footer_read, AVB_FOOTER_SIZE,
-                   f->size - AVB_FOOTER_SIZE)) {
-        error("failed to read footer: %s", strerror(errno));
-        return -1;
-    }
-
-    AvbFooter footer;
-    if (!avb_footer_validate_and_byteswap(&footer_read, &footer)) {
-        debug("invalid avb footer");
-        return -1;
-    }
-    uint64_t vbmeta_offset = footer.vbmeta_offset;
-    uint64_t vbmeta_size = footer.vbmeta_size;
-    check(vbmeta_offset <= f->size - sizeof(footer) - vbmeta_size);
-
-    std::vector<uint8_t> vbmeta_data(vbmeta_size, 0);
-    // TODO(xunchang) handle the sparse image with libsparse.
-    if (!raw_pread(f->fd, vbmeta_data.data(), vbmeta_data.size(),
-                   vbmeta_offset)) {
-        error("failed to read avb vbmeta: %s", strerror(errno));
-        return -1;
-    }
-
-    if (auto status = avb_vbmeta_image_verify(
-            vbmeta_data.data(), vbmeta_data.size(), nullptr, nullptr);
-        status != AVB_VBMETA_VERIFY_RESULT_OK &&
-        status != AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED) {
-        error("failed to verify avb vbmeta, status: %d", status);
-        return -1;
-    }
-    *vbmeta = std::move(vbmeta_data);
-    return 0;
-}
-
-static int parse_avb_image(fec_handle *f, const std::vector<uint8_t> &vbmeta) {
-    // TODO(xunchang) check if avb verification or hashtree is disabled.
-
-    // Look for the hashtree descriptor, we expect exactly one descriptor in
-    // vbmeta.
-    // TODO(xunchang) handle the image with AvbHashDescriptor.
-    auto parse_descriptor = [](const AvbDescriptor *descriptor,
-                               void *user_data) {
-        if (descriptor &&
-            avb_be64toh(descriptor->tag) == AVB_DESCRIPTOR_TAG_HASHTREE) {
-            auto desp = static_cast<const AvbDescriptor **>(user_data);
-            *desp = descriptor;
-            return false;
-        }
-        return true;
-    };
-
-    const AvbHashtreeDescriptor *hashtree_descriptor_ptr = nullptr;
-    avb_descriptor_foreach(vbmeta.data(), vbmeta.size(), parse_descriptor,
-                           &hashtree_descriptor_ptr);
-
-    AvbHashtreeDescriptor hashtree_descriptor;
-    if (!avb_hashtree_descriptor_validate_and_byteswap(hashtree_descriptor_ptr,
-                                                       &hashtree_descriptor)) {
-        error("failed to verify avb hashtree descriptor");
-        return -1;
-    }
-
-    // The partition name, salt, root append right after the hashtree
-    // descriptor.
-    auto read_ptr = reinterpret_cast<const uint8_t *>(hashtree_descriptor_ptr);
-    // Calculate the offset with respect to the vbmeta; and check both the
-    // salt & root are within the range.
-    uint32_t salt_offset =
-        sizeof(AvbHashtreeDescriptor) + hashtree_descriptor.partition_name_len;
-    uint32_t root_offset = salt_offset + hashtree_descriptor.salt_len;
-    check(hashtree_descriptor.salt_len < vbmeta.size());
-    check(salt_offset < vbmeta.size() - hashtree_descriptor.salt_len);
-    check(hashtree_descriptor.root_digest_len < vbmeta.size());
-    check(root_offset < vbmeta.size() - hashtree_descriptor.root_digest_len);
-    std::vector<uint8_t> salt(
-        read_ptr + salt_offset,
-        read_ptr + salt_offset + hashtree_descriptor.salt_len);
-    std::vector<uint8_t> root_hash(
-        read_ptr + root_offset,
-        read_ptr + root_offset + hashtree_descriptor.root_digest_len);
-
-    // Expect the AVB image has the format:
-    // 1. hashtree
-    // 2. ecc data
-    // 3. vbmeta
-    // 4. avb footer
-    check(hashtree_descriptor.fec_offset ==
-          hashtree_descriptor.tree_offset + hashtree_descriptor.tree_size);
-    check(hashtree_descriptor.fec_offset <=
-          f->size - hashtree_descriptor.fec_size);
-
-    f->data_size = hashtree_descriptor.fec_offset;
-
-    f->ecc.blocks = fec_div_round_up(f->data_size, FEC_BLOCKSIZE);
-    f->ecc.rounds = fec_div_round_up(f->ecc.blocks, f->ecc.rsn);
-    f->ecc.size = hashtree_descriptor.fec_size;
-    f->ecc.start = hashtree_descriptor.fec_offset;
-    // TODO(xunchang) verify the integrity of the ecc data.
-    f->ecc.valid = true;
-
-    std::string hash_algorithm =
-        reinterpret_cast<char *>(hashtree_descriptor.hash_algorithm);
-    int nid = -1;
-    if (android::base::EqualsIgnoreCase(hash_algorithm, "sha1")) {
-        nid = NID_sha1;
-    } else if (android::base::EqualsIgnoreCase(hash_algorithm, "sha256")) {
-        nid = NID_sha256;
-    } else {
-        error("unsupported hash algorithm %s", hash_algorithm.c_str());
-    }
-
-    hashtree_info hashtree;
-    hashtree.initialize(hashtree_descriptor.tree_offset,
-                        hashtree_descriptor.tree_offset / FEC_BLOCKSIZE, salt,
-                        nid);
-    if (hashtree.verify_tree(f, root_hash.data()) != 0) {
-        error("failed to verify hashtree");
-        return -1;
-    }
-
-    // We have validate the hashtree,
-    f->data_size = hashtree.hash_start;
-    f->avb = {
-        .valid = true,
-        .vbmeta = vbmeta,
-        .hashtree = std::move(hashtree),
-    };
-
-    return 0;
-}
-
 /* opens `path' using given options and returns a fec_handle in `handle' if
    successful */
 int fec_open(struct fec_handle **handle, const char *path, int mode, int flags,
@@ -687,6 +547,8 @@ int fec_open(struct fec_handle **handle, const char *path, int mode, int flags,
 
     f->data_size = f->size; /* until ecc and/or verity are loaded */
 
+    // Don't parse the avb image if FEC_NO_AVB is set. It's used when libavb is
+    // not supported on mac.
     std::vector<uint8_t> vbmeta;
     if (parse_vbmeta_from_footer(f.get(), &vbmeta) == 0) {
         if (parse_avb_image(f.get(), vbmeta) != 0) {