Add support for hash chaining to detect modifications in postings

The following details of a posting contribute to its hash:

  fullname of account
  string representation of amount

Each posting hashes contributes to the transaction hash, which is compromised
of:

  previous transaction’s hash (as encountered in parsing order)
  actual date
  optional auxiliary date
  optional code
  payee
  hashes of all postings

Note that this means that changes in the “code” or any of the comments

1 files changed, 6 insertions, 3 deletions

diff --git a/src/session.cc b/src/session.cc
index 7cf1a666..6958603e 100644
--- a/src/session.cc
+++ b/src/session.cc
@@ -134,7 +134,7 @@ std::size_t session_t::read_data(const string& master_account)
       parsing_context.push(*price_db_path);
       parsing_context.get_current().journal = journal.get();
       try {
-        if (journal->read(parsing_context) > 0)
+        if (journal->read(parsing_context, HANDLED(hashes)) > 0)
           throw_(parse_error, _("Transactions not allowed in price history file"));
       }
       catch (...) {
@@ -169,7 +169,7 @@ std::size_t session_t::read_data(const string& master_account)
     parsing_context.get_current().journal = journal.get();
     parsing_context.get_current().master  = acct;
     try {
-      xact_count += journal->read(parsing_context);
+      xact_count += journal->read(parsing_context, HANDLED(hashes));
     }
     catch (...) {
       parsing_context.pop();
@@ -230,7 +230,7 @@ journal_t * session_t::read_journal_from_string(const string& data)
   parsing_context.get_current().journal = journal.get();
   parsing_context.get_current().master  = journal->master;
   try {
-    journal->read(parsing_context);
+    journal->read(parsing_context, HANDLED(hashes));
   }
   catch (...) {
     parsing_context.pop();
@@ -331,6 +331,9 @@ option_t<session_t> * session_t::lookup_option(const char * p)
   case 'f':
     OPT_(file_); // -f
     break;
+  case 'h':
+    OPT(hashes);
+    break;
   case 'i':
     OPT(input_date_format_);
     break;