don't calculate sha sums for the certificates over and over

we can use cksum to calculate simple checksum much faster than
with using openssl, so we can compute sums only once

cipherscan

@@ -48,6 +48,10 @@ TIMEOUT=30
 # trust anchors are stored
 CAPATH=""
 SAVECRT=""
+unset known_certs
+declare -A known_certs
+unset cert_checksums
+declare -A cert_checksums
 
 # because running external commands like sleep incurs a fork penalty, we
 # first check if it is necessary
@@ -184,15 +188,25 @@ test_cipher_on_target() {
         for ((i=0; i<$certificate_count; i=i+1 )); do
 
             # extract i'th certificate
-            local cert=$(awk -v i=$i 'split_after == 1 {n++;split_after=0}
-            /-----END CERTIFICATE-----/ {split_after=1}
-            {if (n == i) print }
-            ' <<<"$tmp")
-            # clean up the cert from junk before BEGIN CERTIFICATE
-            cert=$(${OPENSSLBIN} x509 <<<"$cert" 2>/dev/null)
+            local cert=$(awk -v i=$i 'BEGIN { output=0;n=0 }
+            /-----BEGIN CERTIFICATE-----/ { output=1 }
+            output==1 { if (n==i) print }
+            /-----END CERTIFICATE-----/ { output=0; n++ }' <<<"$tmp")
+            # put the output to an array instead awk '{print $1}'
+            local cksum=($(cksum <<<"$cert"))
+            # compare the values not just checksums so that eventual collision
+            # doesn't mess up results
+            if [[ ${known_certs[$cksum]} == $cert ]]; then
+                if [ -n "${current_certificates}" ]; then
+                    current_certificates+=","
+                fi
+                current_certificates+="\"${cert_checksums[$cksum]}\""
+                continue
+            fi
 
             # compute sha256 fingerprint of the certificate
-            local sha256sum=$(${OPENSSLBIN} x509 -outform DER <<<"$cert" 2>/dev/null |\
+            local sha256sum=$(${OPENSSLBIN} x509 -outform DER\
+                <<<"$cert" 2>/dev/null |\
                 ${OPENSSLBIN} dgst -sha256 -r 2>/dev/null| awk '{print $1}')
 
             # check if it is a CA certificate
@@ -238,6 +252,8 @@ test_cipher_on_target() {
                 current_certificates+=","
             fi
             current_certificates+="\"${sha256sum}\""
+            known_certs[$cksum]="$cert"
+            cert_checksums[$cksum]="$sha256sum"
         done
         debug "current_certificates: $current_certificates"