[SCM] GNU libtasn1 branch, master, updated. libtasn1_2_12-3-g0b80a8b

[Nikos Mavrogiannopoulos]

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- Log -----------------------------------------------------------------
commit 0b80a8be08f4b99c5fffbafb0cd7e349cf13f3f1
Author: Nikos Mavrogiannopoulos <address@hidden>
Date:   Sun Apr 1 19:51:53 2012 +0200

    Simplified the overflow tests by using unsigned int numbers, suggested by 
Niels Moeller.

-----------------------------------------------------------------------

Summary of changes:
 lib/decoding.c |   80 +++++++++++++++++++++----------------------------------
 1 files changed, 31 insertions(+), 49 deletions(-)

diff --git a/lib/decoding.c b/lib/decoding.c
index 8f33930..1cfad35 100644
--- a/lib/decoding.c
+++ b/lib/decoding.c
@@ -46,22 +46,6 @@ _asn1_error_description_tag_error (ASN1_TYPE node, char 
*ErrorDescription)
 
 }
 
-inline static int safe_mul(int a, int b)
-{
-  if (INT_MAX/a < b)
-    return INT_MAX;
-  else
-    return a*b;
-}
-
-inline static int safe_add(int a, int b)
-{
-  if (INT_MAX-a < b)
-    return INT_MAX;
-  else
-    return a+b;
-}
-
 /**
  * asn1_get_length_der:
  * @der: DER data to decode.
@@ -77,8 +61,8 @@ inline static int safe_add(int a, int b)
 signed long
 asn1_get_length_der (const unsigned char *der, int der_len, int *len)
 {
-  int ans, sum;
-  int k, punt;
+  unsigned int ans, sum, last;
+  unsigned int k, punt;
 
   *len = 0;
   if (der_len <= 0)
@@ -89,11 +73,6 @@ asn1_get_length_der (const unsigned char *der, int der_len, 
int *len)
       /* short form */
       *len = 1;
       ans = der[0];
-      
-      if (ans > der_len)
-       return -4;
-      
-      return ans;
     }
   else
     {
@@ -105,11 +84,10 @@ asn1_get_length_der (const unsigned char *der, int 
der_len, int *len)
          ans = 0;
          while (punt <= k && punt < der_len)
            {
-             ans = safe_mul(256, ans);
-             if (ans == INT_MAX) return -2;
-             
-             ans = safe_add(der[punt++], ans);
-             if (ans == INT_MAX)
+             last = ans;
+
+             ans = (ans*256) + der[punt++];
+             if (ans < last) 
                /* we wrapped around, no bignum support... */
                return -2;
            }
@@ -121,12 +99,19 @@ asn1_get_length_der (const unsigned char *der, int 
der_len, int *len)
        }
 
       *len = punt;
-      sum = safe_add(ans, *len);
-      if (sum == INT_MAX || sum > der_len)
-       return -4;
-
-      return ans;
     }
+
+  sum = ans + *len;
+  
+  /* check for overflow as well INT_MAX as a maximum upper
+   * limit for length */
+  if (sum >= INT_MAX || sum < ans)
+    return -2;
+  
+  if (sum > der_len)
+    return -4;
+
+  return ans;
 }
 
 /**
@@ -145,7 +130,8 @@ int
 asn1_get_tag_der (const unsigned char *der, int der_len,
                  unsigned char *cls, int *len, unsigned long *tag)
 {
-  int punt, ris;
+  unsigned int punt, ris;
+  unsigned int last;
 
   if (der == NULL || der_len < 2 || len == NULL)
     return ASN1_DER_ERROR;
@@ -164,27 +150,23 @@ asn1_get_tag_der (const unsigned char *der, int der_len,
       ris = 0;
       while (punt <= der_len && der[punt] & 128)
        {
-         ris = safe_mul(128, ris);
-         if (ris == INT_MAX)
-           return ASN1_DER_ERROR;
+         last = ris;
 
-         ris = safe_add(der[punt++] & 0x7F, ris);
-         if (ris == INT_MAX)
-           /* wrapper around, and no bignums... */
+         ris = (ris * 128) + (der[punt++] & 0x7F);
+         if (ris < last)
+           /* wrapped around, and no bignums... */
            return ASN1_DER_ERROR;
        }
+
       if (punt >= der_len)
        return ASN1_DER_ERROR;
-      {
-        ris = safe_mul(128, ris);
-        if (ris == INT_MAX)
-          return ASN1_DER_ERROR;
+
+      last = ris;
         
-        ris = safe_add(der[punt++] & 0x7F, ris);
-       if (ris == INT_MAX)
-         /* wrapper around, and no bignums... */
-         return ASN1_DER_ERROR;
-      }
+      ris = (ris * 128) + (der[punt++] & 0x7F);
+      if (ris < last)
+        return ASN1_DER_ERROR;
+
       *len = punt;
     }
   if (tag)


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