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Initial support for certificate compression

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draft-ietf-tls-certificate-compression specifies a new TLS extension that allows a client to indicate support for receiving the server's certificates in compressed form. This PR adds initial support for that extension to testssl.sh. It was developed based on an announcement that facebook.com has implemented support for the extension.

This PR does not add a test for a server's support for the new extension, it just adds code to parse_tls_serverhello() that will parse a compressed certificate message if one is present in the server's response. So, in practice, the code in this PR will not actually be used until additional code has been added that sends a ClientHello with the compress_certificate extension.

The code in this PR can be tested by using the --devel option and by changing line 19347 from

     tls_sockets "$TLS_LOW_BYTE" "$HEX_CIPHER" "ephemeralkey"

to

     tls_sockets "$TLS_LOW_BYTE" "$HEX_CIPHER" "all+" "00,1b, 00,03, 02, 00,01"

testssl.sh can then be called using

     testssl.sh --debug 3 --devel 04 "13,01" facebook.com

Note that this PR adds a test for zlib support to find_openssl_binary(). The test uses $OPENSSL zlib in the same way it is used in parse_tls_serverhello(). The test asks $OPENSSL zlib to uncompress the compressed version of the string "zlib" and the checks to see whether the decompression was performed correctly. There is already a test for zlib support in run_crime(), but I did not check to see whether the check in run_crime() could be replaced with a check of the new $HAS_ZLIB variable.
This commit is contained in:
David Cooper 2019-06-06 12:06:10 -04:00
parent 91e98f1fc3
commit e2042e99d6
1 changed files with 34 additions and 0 deletions
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testssl.sh
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@ -351,6 +351,7 @@ HAS_IRC=false
HAS_CHACHA20=false
HAS_AES128_GCM=false
HAS_AES256_GCM=false
HAS_ZLIB=false
OSSL_CIPHERS_S=""
PORT=443 # unless otherwise auto-determined, see below
NODE=""
@ -11587,6 +11588,7 @@ parse_tls_serverhello() {
16) tmln_out " (certificate_status)" ;;
17) tmln_out " (supplemental_data)" ;;
18) tmln_out " (key_update)" ;;
19) tmln_out " (compressed_certificate)" ;;
FE) tmln_out " (message_hash)" ;;
*) tmln_out ;;
esac
@ -11646,6 +11648,36 @@ parse_tls_serverhello() {
fi
tls_certificate_status_ascii="${tls_handshake_ascii:i:msg_len}"
tls_certificate_status_ascii_len=$msg_len
elif [[ "$tls_msg_type" == 19 ]]; then
if [[ -n "$tls_certificate_ascii" ]]; then
debugme tmln_warning "Response contained more than one Certificate handshake message."
[[ $DEBUG -ge 1 ]] && tmpfile_handle ${FUNCNAME[0]}.txt
return 1
fi
if [[ $DEBUG -ge 3 ]]; then
tm_out " Certificate Compression Algorithm: ${tls_handshake_ascii:i:4}"
case ${tls_handshake_ascii:i:4} in
0001) tmln_out " (ZLIB)" ;;
0002) tmln_out " (Brotli)" ;;
0003) tmln_out " (Zstandard)" ;;
*) tmln_out ;;
esac
offset=$((i+4))
tmln_out " Uncompressed certificate length: $(printf "%d" 0x${tls_handshake_ascii:offset:6})"
tmln_out
fi
if [[ "$process_full" =~ all ]] && "$HAS_ZLIB" && [[ "${tls_handshake_ascii:i:4}" == 0001 ]]; then
offset=$((i+4))
tls_certificate_ascii_len=2*0x${tls_handshake_ascii:offset:6}
offset=$((i+16))
len1=$((msg_len-16))
tls_certificate_ascii="$(asciihex_to_binary_file "${tls_handshake_ascii:offset:len1}" /dev/stdout | $OPENSSL zlib -d 2>/dev/null | hexdump -v -e '16/1 "%02X"')"
tls_certificate_ascii="${tls_certificate_ascii%%[!0-9A-F]*}"
if [[ ${#tls_certificate_ascii} -ne $tls_certificate_ascii_len ]]; then
debugme tmln_warning "Length of uncompressed certificates did not match specified length."
return 1
fi
fi
fi
done
@ -16556,6 +16588,8 @@ find_openssl_binary() {
$OPENSSL enc -aes-256-gcm -K 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef -iv 0123456789abcdef01234567 > /dev/null 2> /dev/null <<< "test"
[[ $? -eq 0 ]] && HAS_AES256_GCM=true
[[ "$(echo -e "\x78\x9C\xAB\xCA\xC9\x4C\xE2\x02\x00\x06\x20\x01\xBC" | $OPENSSL zlib -d 2>/dev/null)" == zlib ]] && HAS_ZLIB=true
if [[ "$OPENSSL_TIMEOUT" != "" ]]; then
if type -p timeout >/dev/null 2>&1; then
if ! "$do_mass_testing"; then