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サーバ側と通信するCipher suite (暗号スイート) の調査方法

備忘のためのメモ。今回は例としてS3のs3.amazonaws.comに対して色々と情報を見たいと思います。

暗号スイートとは？

こちらのサイトがわかりやすかったです。

https://pkiwithadcs.com/cipher_suite/

利用可能な暗号スイートの確認

nmap --script ssl-enum-ciphers -p 443 s3.amazonaws.com

[ec2-user@bastin ~]$ nmap --script ssl-enum-ciphers -p 443 s3.amazonaws.com

Starting Nmap 6.40 ( http://nmap.org ) at 2022-04-12 11:51 JST
Nmap scan report for s3.amazonaws.com (52.217.129.136)
Host is up (0.16s latency).
rDNS record for 52.217.129.136: s3-1.amazonaws.com
PORT    STATE SERVICE
443/tcp open  https
| ssl-enum-ciphers: 
|   TLSv1.0: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - strong
|       TLS_RSA_WITH_3DES_EDE_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_256_GCM_SHA384 - strong
|     compressors: 
|       NULL
|   TLSv1.1: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - strong
|       TLS_RSA_WITH_3DES_EDE_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_256_GCM_SHA384 - strong
|     compressors: 
|       NULL
|   TLSv1.2: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 - strong
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - strong
|       TLS_RSA_WITH_3DES_EDE_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA - strong
|       TLS_RSA_WITH_AES_128_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_128_GCM_SHA256 - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA - strong
|       TLS_RSA_WITH_AES_256_CBC_SHA256 - strong
|       TLS_RSA_WITH_AES_256_GCM_SHA384 - strong
|     compressors: 
|       NULL
|_  least strength: strong

Nmap done: 1 IP address (1 host up) scanned in 7.09 seconds
[ec2-user@bastin ~]$

SSL Server Testで確認

どの暗号スイートを使うのかの優先順位がわかる

https://www.ssllabs.com/ssltest/analyze.html?d=s3.amazonaws.com

image-20220412115428226

S3に対して実際に通信を行う

TLSv1.2のECDHE-RSA-AES128-GCM-SHA256を使って通信をしているようだ。

[ec2-user@bastin ~]$ openssl s_client -connect s3.amazonaws.com:443 < /dev/null
CONNECTED(00000003)
depth=2 C = US, O = Amazon, CN = Amazon Root CA 1
verify return:1
depth=1 C = US, O = Amazon, OU = Server CA 1B, CN = Amazon
verify return:1
depth=0 CN = s3.amazonaws.com
verify return:1
---
Certificate chain
 0 s:/CN=s3.amazonaws.com
 ～省略～
---
No client certificate CA names sent
Peer signing digest: SHA256
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 5893 bytes and written 415 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: 76E616AE11A2D6B01B11496893D0D0B966E0980757F14B7397D9A1C0FB3C1512
    Session-ID-ctx: 
    Master-Key: 588AB3813C66F79A3874BF67F4D11EC3F12B3FBC25C317C384EC111119B9E854D570DCE2DCEA7832D25E70E4AD1AF99F
    Key-Arg   : None
    Krb5 Principal: None
    PSK identity: None
    PSK identity hint: None
    Start Time: 1649731926
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---
DONE

暗号スイート名 と OpenSSL での名称の対応表

opensslと一般的な暗号スイート名は一致していないので対応表を見つつ、これはどれだ？というのを見つける必要がある

https://www.ipa.go.jp/security/ipg/documents/tls_cipher_suite_config_20200707.pdf

TLS 暗号設定 暗号スイートの設定例

1.1.3. 一般的な名称と OpenSSL での名称の対応表

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