[GNUnet-SVN] [taler-bank] branch master updated: check if parsed numbers do not exceed 2^53 - 1, as for the well known JavaScript limit.

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marcello pushed a commit to branch master
in repository bank.

The following commit(s) were added to refs/heads/master by this push:
     new 0ff63bf  check if parsed numbers do not exceed 2^53 - 1, as for the 
well known JavaScript limit.
0ff63bf is described below

commit 0ff63bf08ff3ffb1e8ad50fd110185e1d8b8f4ef
Author: Marcello Stanisci <address@hidden>
AuthorDate: Wed May 2 15:14:36 2018 +0200

    check if parsed numbers do not exceed 2^53 - 1,
    as for the well known JavaScript limit.
---
 talerbank/app/amount.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/talerbank/app/amount.py b/talerbank/app/amount.py
index 814b9e0..022d108 100644
--- a/talerbank/app/amount.py
+++ b/talerbank/app/amount.py
@@ -30,6 +30,12 @@ class CurrencyMismatch(Exception):
             "%s vs %s" % (curr1, curr2))
 
 
+class AmountOverflow(Exception):
+    hint = "Overflowing amount"
+    def __init__(self, part) -> None:
+        super(BadFormatAmount, self).__init__(
+            "This part exceedes 2^53 -1: " + part)
+
 class BadFormatAmount(Exception):
     hint = "Amount given was incorrect"
     def __init__(self, faulty_str) -> None:
@@ -70,10 +76,33 @@ class Amount:
         parsed = re.search(exp, amount_str)
         if not parsed:
             raise BadFormatAmount(amount_str)
+
+        # True if overflows.
+        def check_overflow(arg):
+            # Comes from 2^53 - 1
+            JAVASCRIPT_MAX_INT = "9007199254740991"
+            if len(JAVASCRIPT_MAX_INT) < len(arg):
+                return True
+            if len(JAVASCRIPT_MAX_INT) == len(arg):
+                # Assume current system can afford to store
+                # a number as big as JAVASCRIPT_MAX_INT.
+                tmp = int(arg)
+                tmp_js = int(JAVASCRIPT_MAX_INT)
+                
+                if tmp > tmp_js - 1: # - 1 leaves room for the fractional part
+                    return True
+            return False
+
+        if check_overflow(parsed.group(2)):
+            raise AmountOverflow("integer part")
+
         value = int(parsed.group(2))
         fraction = 0
         for i, digit in enumerate(parsed.group(3) or "0"):
             fraction += int(int(digit) * (Amount._fraction() / 10 ** (i+1)))
+            if check_overflow(str(fraction)):
+                raise AmountOverflow("fraction")
+
         return cls(parsed.group(1), value, fraction)
 
     # Comare two amounts, return:

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