From 3025d92ebf5112ea11a0ce025aed095435e0de27 Mon Sep 17 00:00:00 2001
From: David Cooper <david.cooper@nist.gov>
Date: Tue, 4 Feb 2020 14:55:53 -0500
Subject: [PATCH] Fix public key length calculation

This PR fixes a minor bug in get_pub_key_size(). If the key size is being determined manually and length encoding requires 4 bytes, then the current code computes the length incorrectly. This is a very insignificant bug, since does not apply to RSA or ECC keys, and the key would have to be at least 16 megabytes long for it to require 4 bytes to encode.

This PR also cleans up get_pub_key_size() a bit by replacing `i=$i+...` with `i+=...` and by enclosing math in `$(( ... ))`.
---
 testssl.sh | 58 +++++++++++++++++++++++++++---------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/testssl.sh b/testssl.sh
index 8ec6a5f..249e5d3 100755
--- a/testssl.sh
+++ b/testssl.sh
@@ -10503,83 +10503,83 @@ get_pub_key_size() {
           i=2
           len1="0x${pubkey:i:2}"
           if [[ $len1 -lt 0x80 ]]; then
-               i=$i+2
+               i+=2
           else
-               len1=$len1-0x80
-               i=$i+2*$len1+2
+               len1=$((len1-0x80))
+               i+=$((2*len1+2))
           fi
 
           # Skip over algorithm field
-          i=$i+2
+          i+=2
           len1="0x${pubkey:i:2}"
-          i=$i+2
+          i+=2
           if [[ $len1 -lt 0x80 ]]; then
-               i=$i+2*$len1
+               i+=$((2*len1))
           else
                case $len1 in
                     129) len="0x${pubkey:i:2}" ;;
                     130) len="0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
                          ;;
                     131) len="0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
                          ;;
                     132) len="0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
                          ;;
                esac
-               i=$i+2+2*$len
+               i+=$((2+2*len))
           fi
 
           # Next is the public key BIT STRING. Skip over tag, length, and number of unused bits.
-          i=$i+2
+          i+=2
           len1="0x${pubkey:i:2}"
           if [[ $len1 -lt 0x80 ]]; then
-               i=$i+4
+               i+=4
           else
-               len1=$len1-0x80
-               i=$i+2*$len1+4
+               len1=$((len1-0x80))
+               i+=$((2*len1+4))
           fi
 
           # Now get the length of the public key
-          i=$i+2
+          i+=2
           len1="0x${pubkey:i:2}"
-          i=$i+2
+          i+=2
           if [[ $len1 -lt 0x80 ]]; then
                len=$len1
           else
                case $len1 in
                     129) len="0x${pubkey:i:2}" ;;
                     130) len="0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
                          ;;
                     131) len="0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
-                         i=$i+2
+                         i+=2
                          len=256*$len+"0x${pubkey:i:2}"
                          ;;
                     132) len="0x${pubkey:i:2}"
-                         i=$i+2
-                         len=256*"0x${pubkey:i:2}"
-                         i=$i+2
-                         len=256*"0x${pubkey:i:2}"
-                         i=$i+2
-                         len=256*"0x${pubkey:i:2}"
+                         i+=2
+                         len=256*$len+"0x${pubkey:i:2}"
+                         i+=2
+                         len=256*$len+"0x${pubkey:i:2}"
+                         i+=2
+                         len=256*$len+"0x${pubkey:i:2}"
                          ;;
                esac
           fi
-          len=8*$len # convert from bytes to bits
+          len=$((8*len)) # convert from bytes to bits
           pubkeybits="$(printf "%d" $len)"
           echo "Server public key is $pubkeybits bit" >> $TMPFILE
      fi