Add support of more hash algorithms for verity tree builder

Currently, verified boot 1.0 is using SHA256 to compute the hash tree
while AVB is using SHA1. We should support at least these two hash
functionss in the HashTreeBuilder and command line parser. And we can
potentially add more algorithms in the future.

Bug: 25170618
Test: unit tests pass
Change-Id: I5f6dc8a545c0cef75acbbc2044959e8100f9f842

1 files changed, 17 insertions, 2 deletions

diff --git a/verity/build_verity_tree_main.cpp b/verity/build_verity_tree_main.cpp
index 9eaaa79e..76164cc5 100644
--- a/verity/build_verity_tree_main.cpp
+++ b/verity/build_verity_tree_main.cpp
@@ -52,6 +52,7 @@ int main(int argc, char** argv) {
   bool sparse = false;
   uint64_t calculate_size = 0;
   bool verbose = false;
+  std::string hash_algorithm;
 
   while (1) {
     constexpr struct option long_options[] = {
@@ -61,8 +62,10 @@ int main(int argc, char** argv) {
         {"sparse", no_argument, nullptr, 'S'},
         {"verity-size", required_argument, nullptr, 's'},
         {"verbose", no_argument, nullptr, 'v'},
+        {"hash-algorithm", required_argument, nullptr, 0},
         {nullptr, 0, nullptr, 0}};
-    int c = getopt_long(argc, argv, "a:A:hSs:v", long_options, nullptr);
+    int option_index;
+    int c = getopt_long(argc, argv, "a:A:hSs:v", long_options, &option_index);
     if (c < 0) {
       break;
     }
@@ -102,6 +105,12 @@ int main(int argc, char** argv) {
       case 'v':
         verbose = true;
         break;
+      case 0: {
+        std::string option = long_options[option_index].name;
+        if (option == "hash-algorithm") {
+          hash_algorithm = optarg;
+        }
+      } break;
       case '?':
         usage();
         return 1;
@@ -113,7 +122,13 @@ int main(int argc, char** argv) {
   argc -= optind;
   argv += optind;
 
-  HashTreeBuilder builder(kBlockSize);
+  auto hash_function = hash_algorithm.empty()
+                           ? EVP_sha256()
+                           : HashTreeBuilder::HashFunction(hash_algorithm);
+  if (hash_function == nullptr) {
+    return 1;
+  }
+  HashTreeBuilder builder(kBlockSize, hash_function);
 
   if (calculate_size) {
     if (argc != 0) {