Revised parse_tls_serverhello()
Revised parse_tls_serverhello() to more carefully check the response for errors, and to provide for more flexibility (e.g., if handshake messages are split across multiple fragments).
This commit is contained in:
David Cooper
parent
4eefe0df8b
commit
cba7fddbdd
304
testssl.sh
304
testssl.sh
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@ -4011,92 +4011,268 @@ parse_sslv2_serverhello() {
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# arg1: name of file with socket reply
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# arg1: name of file with socket reply
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parse_tls_serverhello() {
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parse_tls_serverhello() {
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local tls_hello_ascii=$(hexdump -v -e '16/1 "%02X"' "$1")
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local tls_hello_ascii=$(hexdump -v -e '16/1 "%02X"' "$1")
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local tls_content_type tls_protocol tls_len_all
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local tls_handshake_ascii="" tls_alert_ascii=""
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#TODO: all vars here
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local -i tls_hello_ascii_len tls_handshake_ascii_len tls_alert_ascii_len msg_len
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local tls_serverhello_ascii=""
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local -i tls_serverhello_ascii_len=0
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local tls_alert_descrip
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local -i tls_sid_len offset
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local tls_msg_type tls_content_type tls_protocol tls_protocol2 tls_hello_time
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local tls_err_level tls_err_descr tls_cipher_suite tls_compression_method
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local -i i
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TLS_TIME=""
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TLS_TIME=""
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DETECTED_TLS_VERSION=""
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DETECTED_TLS_VERSION=""
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# server hello, handshake details see http://en.wikipedia.org/wiki/Transport_Layer_Security-SSL#TLS_record
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# $tls_hello_ascii may contain trailing whitespace. Remove it:
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tls_hello_ascii="${tls_hello_ascii%%[!0-9A-F]*}"
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[[ "$DEBUG" -eq 5 ]] && echo $tls_hello_ascii # one line without any blanks
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# Client messages, including handshake messages, are carried by the record layer.
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# First, extract the handshake and alert messages.
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# see http://en.wikipedia.org/wiki/Transport_Layer_Security-SSL#TLS_record
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# byte 0: content type: 0x14=CCS, 0x15=TLS alert x16=Handshake, 0x17 Aplication, 0x18=HB
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# byte 0: content type: 0x14=CCS, 0x15=TLS alert x16=Handshake, 0x17 Aplication, 0x18=HB
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# byte 1+2: TLS version word, major is 03, minor 00=SSL3, 01=TLS1 02=TLS1.1 03=TLS 1.2
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# byte 1+2: TLS version word, major is 03, minor 00=SSL3, 01=TLS1 02=TLS1.1 03=TLS 1.2
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# byte 3+4: length all
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# byte 3+4: fragment length
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# byte 5: handshake type (2=hello) TLS alert: level (2=fatal), descr (0x28=handshake failure)
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# bytes 5...: message fragment
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# byte 6+7+8: length server hello
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tls_hello_ascii_len=${#tls_hello_ascii}
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# byte 9+10: 03, TLS version word see byte 1+2
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if [[ $DEBUG -ge 2 ]] && [[ $tls_hello_ascii_len -gt 0 ]]; then
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# byte 11-14: TLS timestamp for OpenSSL <1.0.1f
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echo "TLS message fragments:"
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# byte 15-42: random, 28 bytes
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# byte 43: session id length
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# byte 44+45+sid-len: cipher suite!
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# byte 46+sid-len: compression method: 00: none, 01: deflate
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# byte 47+48+sid-len: extension length
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[[ "$DEBUG" -eq 5 ]] && echo $tls_hello_ascii # one line without any blanks
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if [[ -z "$tls_hello_ascii" ]]; then
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debugme echo "server hello empty, TCP connection closed"
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return 1 # no server hello received
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fi
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fi
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for (( i=0; i<tls_hello_ascii_len; i=i+msg_len )); do
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if [[ $tls_hello_ascii_len-$i -lt 10 ]]; then
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# This could just be a result of the server's response being
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# split across two or more packets.
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continue
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fi
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tls_content_type="${tls_hello_ascii:i:2}"
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i=$i+2
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tls_protocol="${tls_hello_ascii:i:4}"
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i=$i+4
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msg_len=2*$(hex2dec "${tls_hello_ascii:i:4}")
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i=$i+4
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# now scrape two bytes out of the reply per byte
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tls_content_type="${tls_hello_ascii:0:2}" # normally this is x16 (Handshake) here
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tls_protocol="${tls_hello_ascii:2:4}"
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DETECTED_TLS_VERSION=$tls_protocol
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tls_len_all=${tls_hello_ascii:6:4}
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sid_len_offset=86
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tls_hello="${tls_hello_ascii:10:2}" # normally this is x02
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tls_protocol2="${tls_hello_ascii:18:4}"
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tls_hello_time="${tls_hello_ascii:22:8}"
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if [[ $tls_content_type == "15" ]]; then # TLS ALERT
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tls_err_level=${tls_hello_ascii:10:2} # 1: warning, 2: fatal
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tls_err_descr=${tls_hello_ascii:12:2} # 112/0x70: Unrecognized name, 111/0x6F: certificate_unobtainable,
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# 113/0x71: bad_certificate_status_response, #114/0x72: bad_certificate_hash_value
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if [[ $DEBUG -ge 2 ]]; then
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if [[ $DEBUG -ge 2 ]]; then
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echo "tls_protocol (reclyr): 0x$tls_protocol"
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echo " tls_protocol (reclyr): 0x$tls_protocol"
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echo "tls_content_type: 0x$tls_content_type"
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out " tls_content_type: 0x$tls_content_type"
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echo "tls_len_all: $tls_len_all"
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case $tls_content_type in
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echo "tls_err_descr: 0x${tls_err_descr} / = $(hex2dec ${tls_err_descr})"
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15) outln " (alert)" ;;
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echo "tls_err_level: ${tls_err_level} (warning:1, fatal:2)"
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16) outln " (handshake)" ;;
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*) outln ;;
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esac
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echo " msg_len: $((msg_len/2))"
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outln
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fi
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fi
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# now, here comes a strange thing... -- on the first glance
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if [[ $tls_content_type != "15" ]] && [[ $tls_content_type != "16" ]]; then
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# IF an apache 2.2/2.4 server e.g. has a default servername configured but we send SNI <myhostname>
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debugme pr_svrty_criticalln "Content type other than alert or handshake detected."
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# we get a TLS ALERT saying "unrecognized_name" (0x70) and a warning (0x1), see RFC https://tools.ietf.org/html/rfc6066#page-17
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return 1
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# note that RFC recommended to fail instead: https://tools.ietf.org/html/rfc6066#section-3
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elif [[ "${tls_protocol:0:2}" != "03" ]]; then
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# we need to handle this properly -- otherwise we always return that the protocol or cipher is not available!
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debugme pr_svrty_criticalln "Protocol record_version.major is not 03."
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if [[ "$tls_err_descr" == 70 ]] && [[ "${tls_err_level}" == "01" ]]; then
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sid_len_offset=100 # we are 2x7 bytes off (formerly: 86 instead of 100)
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tls_hello="${tls_hello_ascii:24:2}" # here, too (normally this is (02)
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tls_protocol2="${tls_hello_ascii:32:4}" # here, too
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tls_hello_time="${tls_hello_ascii:36:8}" # and here, too
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else
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return 1
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return 1
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fi
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fi
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DETECTED_TLS_VERSION=$tls_protocol
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if [[ $msg_len -gt $tls_hello_ascii_len-$i ]]; then
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# This could just be a result of the server's response being
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# split across two or more packets. Just grab the part that
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# is available.
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msg_len=$tls_hello_ascii_len-$i
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fi
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fi
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TLS_TIME=$(hex2dec "$tls_hello_time")
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if [[ $tls_content_type == "16" ]]; then
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tls_sid_len=$(hex2dec "${tls_hello_ascii:$sid_len_offset:2}")
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tls_handshake_ascii="$tls_handshake_ascii${tls_hello_ascii:i:msg_len}"
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let sid_offset=$sid_len_offset+2+$tls_sid_len*2
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elif [[ $tls_content_type == "15" ]]; then # TLS ALERT
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tls_cipher_suite="${tls_hello_ascii:$sid_offset:4}"
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tls_alert_ascii="$tls_alert_ascii${tls_hello_ascii:i:msg_len}"
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let sid_offset=$sid_len_offset+6++$tls_sid_len*2
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fi
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tls_compression_method="${tls_hello_ascii:$sid_offset:2}"
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done
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# Now check the alert messages.
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tls_alert_ascii_len=${#tls_alert_ascii}
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if [[ $tls_alert_ascii_len -gt 0 ]]; then
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debugme echo "TLS alert messages:"
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for (( i=0; i+3 < tls_alert_ascii_len; i=i+4 )); do
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tls_err_level=${tls_alert_ascii:i:2} # 1: warning, 2: fatal
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j=$i+2
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tls_err_descr=${tls_alert_ascii:j:2} # 112/0x70: Unrecognized name, 111/0x6F: certificate_unobtainable,
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# 113/0x71: bad_certificate_status_response, #114/0x72: bad_certificate_hash_value
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debugme out " tls_err_descr: 0x${tls_err_descr} / = $(hex2dec ${tls_err_descr})"
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case $tls_err_descr in
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00) tls_alert_descrip="close notify" ;;
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0A) tls_alert_descrip="unexpected message" ;;
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14) tls_alert_descrip="bad record mac" ;;
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15) tls_alert_descrip="decryption failed" ;;
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16) tls_alert_descrip="record overflow" ;;
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1E) tls_alert_descrip="decompression failure" ;;
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28) tls_alert_descrip="handshake failure" ;;
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29) tls_alert_descrip="no certificate RESERVED" ;;
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2A) tls_alert_descrip="bad certificate" ;;
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2B) tls_alert_descrip="unsupported certificate" ;;
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2C) tls_alert_descrip="certificate revoked" ;;
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2D) tls_alert_descrip="certificate expired" ;;
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2E) tls_alert_descrip="certificate unknown" ;;
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2F) tls_alert_descrip="illegal parameter" ;;
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30) tls_alert_descrip="unknown ca" ;;
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31) tls_alert_descrip="access denied" ;;
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32) tls_alert_descrip="decode error" ;;
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33) tls_alert_descrip="decrypt error" ;;
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3C) tls_alert_descrip="export restriction RESERVED" ;;
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46) tls_alert_descrip="protocol version" ;;
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47) tls_alert_descrip="insufficient security" ;;
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50) tls_alert_descrip="internal error" ;;
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56) tls_alert_descrip="inappropriate fallback" ;;
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5A) tls_alert_descrip="user canceled" ;;
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64) tls_alert_descrip="no renegotiation" ;;
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6E) tls_alert_descrip="unsupported extension" ;;
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6F) tls_alert_descrip="certificate unobtainable" ;;
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70) tls_alert_descrip="unrecognized name" ;;
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71) tls_alert_descrip="bad certificate status response" ;;
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72) tls_alert_descrip="bad certificate hash value" ;;
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73) tls_alert_descrip="unknown psk identity" ;;
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78) tls_alert_descrip="no application protocol" ;;
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*) tls_alert_descrip="$(hex2dec "$tls_err_descr")";;
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esac
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if [[ $DEBUG -ge 2 ]]; then
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if [[ $DEBUG -ge 2 ]]; then
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echo "tls_protocol (reclyr): 0x$tls_protocol"
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outln " ($tls_alert_descrip)"
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echo "tls_hello: 0x$tls_hello"
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out " tls_err_level: ${tls_err_level}"
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if [[ $DEBUG -ge 4 ]]; then
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case $tls_err_level in
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echo "tls_protocol: 0x$tls_protocol2"
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01) outln " (warning)" ;;
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echo "tls_sid_len: 0x$(dec2hex $tls_sid_len) / = $tls_sid_len"
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02) outln " (fatal)" ;;
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*) outln ;;
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esac
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outln
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fi
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fi
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echo -n "tls_hello_time: 0x$tls_hello_time "
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if [[ "$tls_err_level" != "01" ]] && [[ "$tls_err_level" != "02" ]]; then
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debugme pr_svrty_criticalln "Unexpected AlertLevel (0x$tls_err_level)."
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return 1
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elif [[ "$tls_err_level" == "02" ]]; then
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# Fatal alert
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return 1
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fi
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done
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fi
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# Now extract just the server hello handshake message.
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tls_handshake_ascii_len=${#tls_handshake_ascii}
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if [[ $DEBUG -ge 2 ]] && [[ $tls_handshake_ascii_len -gt 0 ]]; then
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echo "TLS handshake messages:"
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fi
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for (( i=0; i<tls_handshake_ascii_len; i=i+msg_len )); do
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if [[ $tls_handshake_ascii_len-$i -lt 8 ]]; then
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# This could just be a result of the server's response being
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# split across two or more packets.
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continue
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fi
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tls_msg_type="${tls_handshake_ascii:i:2}"
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i=$i+2
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msg_len=2*$(hex2dec "${tls_handshake_ascii:i:6}")
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i=$i+6
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if [[ $DEBUG -ge 2 ]]; then
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out " handshake type: 0x${tls_msg_type}"
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case $tls_msg_type in
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00) outln " (hello_request)" ;;
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01) outln " (client_hello)" ;;
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02) outln " (server_hello)" ;;
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03) outln " (hello_verify_request)" ;;
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04) outln " (NewSessionTicket)" ;;
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0B) outln " (certificate)" ;;
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0C) outln " (server_key_exchange)" ;;
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0D) outln " (certificate_request)" ;;
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0E) outln " (server_hello_done)" ;;
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0F) outln " (certificate_verify)" ;;
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10) outln " (client_key_exchange)" ;;
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14) outln " (finished)" ;;
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15) outln " (certificate_url)" ;;
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16) outln " (certificate_status)" ;;
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17) outln " (supplemental_data)" ;;
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*) outln ;;
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esac
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echo " msg_len: $((msg_len/2))"
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outln
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fi
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if [[ $msg_len -gt $tls_handshake_ascii_len-$i ]]; then
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# This could just be a result of the server's response being
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# split across two or more packets. Just grab the part that
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# is available.
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msg_len=$tls_handshake_ascii_len-$i
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fi
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if [[ "$tls_msg_type" == "02" ]]; then
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if [[ -n "$tls_serverhello_ascii" ]]; then
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debugme pr_svrty_criticalln "Response contained more than one ServerHello handshake message."
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return 1
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fi
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tls_serverhello_ascii="${tls_handshake_ascii:i:msg_len}"
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tls_serverhello_ascii_len=$msg_len
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fi
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done
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if [[ $tls_serverhello_ascii_len -eq 0 ]]; then
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debugme echo "server hello empty, TCP connection closed"
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return 1 # no server hello received
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elif [[ $tls_serverhello_ascii_len -lt 76 ]]; then
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debugme echo "Malformed response"
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return 1
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elif [[ "${tls_handshake_ascii:0:2}" != "02" ]]; then
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# the ServerHello MUST be the first handshake message
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debugme pr_svrty_criticalln "The first handshake protocol message is not a ServerHello."
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return 1
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fi
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# Parse the server hello handshake message
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# byte 0+1: 03, TLS version word see byte 1+2
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# byte 2-5: TLS timestamp for OpenSSL <1.01f
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# byte 6-33: random, 28 bytes
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# byte 34: session id length
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# byte 35+36+sid-len: cipher suite!
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# byte 37+sid-len: compression method: 00: none, 01: deflate, 64: LZS
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# byte 38+39+sid-len: extension length
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tls_protocol2="${tls_serverhello_ascii:0:4}"
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if [[ "${tls_protocol2:0:2}" != "03" ]]; then
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debugme pr_svrty_criticalln "server_version.major in ServerHello is not 03."
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return 1
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fi
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DETECTED_TLS_VERSION="$tls_protocol2"
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tls_hello_time="${tls_serverhello_ascii:4:8}"
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TLS_TIME=$(hex2dec "$tls_hello_time")
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tls_sid_len=2*$(hex2dec "${tls_serverhello_ascii:68:2}")
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let offset=70+$tls_sid_len
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if [[ $tls_serverhello_ascii_len -lt 76+$tls_sid_len ]]; then
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debugme echo "Malformed response"
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return 1
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fi
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tls_cipher_suite="${tls_serverhello_ascii:$offset:4}"
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let offset=74+$tls_sid_len
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tls_compression_method="${tls_serverhello_ascii:$offset:2}"
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if [[ $DEBUG -ge 2 ]]; then
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echo "TLS server hello message:"
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if [[ $DEBUG -ge 4 ]]; then
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tls_sid_len=$tls_sid_len/2
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echo " tls_protocol: 0x$tls_protocol2"
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echo " tls_sid_len: 0x$(dec2hex $tls_sid_len) / = $tls_sid_len"
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fi
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echo -n " tls_hello_time: 0x$tls_hello_time "
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if "$HAS_GNUDATE"; then
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if "$HAS_GNUDATE"; then
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date --date="@$TLS_TIME" "+%Y-%m-%d %r"
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date --date="@$TLS_TIME" "+%Y-%m-%d %r"
|
||||||
else
|
else
|
||||||
LC_ALL=C date -j -f %s "$TLS_TIME" "+%Y-%m-%d %r"
|
LC_ALL=C date -j -f %s "$TLS_TIME" "+%Y-%m-%d %r"
|
||||||
fi
|
fi
|
||||||
echo "tls_cipher_suite: 0x$tls_cipher_suite"
|
echo " tls_cipher_suite: 0x$tls_cipher_suite"
|
||||||
echo "tls_compression_method: 0x$tls_compression_method"
|
echo -n " tls_compression_method: 0x$tls_compression_method "
|
||||||
|
case $tls_compression_method in
|
||||||
|
00) echo "(NONE)" ;;
|
||||||
|
01) echo "(zlib compression)" ;;
|
||||||
|
40) echo "(LZS compression)" ;;
|
||||||
|
*) echo "(unrecognized compression method)" ;;
|
||||||
|
esac
|
||||||
outln
|
outln
|
||||||
fi
|
fi
|
||||||
return 0
|
return 0
|
||||||
|
|
|
||||||
Loading…
Reference in New Issue