openssl可以用于和服务器端建立ssl连接，并且输出相关信息，通过相关信息，可以看出建立连接的过程是否正常。当使用应用系统的客户端通过https访问服务器的时候，总是出现报错，又找不到错误原因的时候，可以使用openssl模拟客户端请求，建立ssl连接并输出相关信息来查找失败原因。
1. ssl验证失败案例
openssl s_client -connect server:443
这里的server是指服务器的域名或者ip地址。
# openssl s_client -connect otp.com:443
CONNECTED(00000003)
depth=0 CN = otp.com, subjectAltName = "DNS:otp.com,DNS:mail.otp.com,DNS:WIN-IRDSVJO3UTT.otp.com,DNS:autodiscover.otp.com"
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 CN = otp.com, subjectAltName = "DNS:otp.com,DNS:mail.otp.com,DNS:WIN-IRDSVJO3UTT.otp.com,DNS:autodiscover.otp.com"
verify error:num=21:unable to verify the first certificate
verify return:1
depth=0 CN = otp.com, subjectAltName = "DNS:otp.com,DNS:mail.otp.com,DNS:WIN-IRDSVJO3UTT.otp.com,DNS:autodiscover.otp.com"
verify return:1
---
Certificate chain
0 s:CN = otp.com, subjectAltName = "DNS:otp.com,DNS:mail.otp.com,DNS:WIN-IRDSVJO3UTT.otp.com,DNS:autodiscover.otp.com"
i:C = cn, ST = bj, L = bj, O = ft, CN = otp.com
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=CN = otp.com, subjectAltName = "DNS:otp.com,DNS:mail.otp.com,DNS:WIN-IRDSVJO3UTT.otp.com,DNS:autodiscover.otp.com"
issuer=C = cn, ST = bj, L = bj, O = ft, CN = otp.com
---
No client certificate CA names sent
Peer signing digest: SHA512
Peer signature type: RSA
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 1592 bytes and written 431 bytes
Verification error: unable to verify the first certificate
---
New, TLSv1.2, 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: 4737CE4AD984C6F94284B5557098798759250FA2D54C736772134B26D87C2B53
Session-ID-ctx:
Master-Key: 258A8B01F4ED39E3D482F000B1072697C4F35009AA01E6ADB3A69E2A606F1B5B3A073AB6FD87B86C488DC67D54955C14
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 300 (seconds)
TLS session ticket:
0000 - f0 8f 20 e0 7d a8 39 b6-98 5c cf c6 47 68 52 5f .. .}.9..\..GhR_
0010 - 01 30 a5 8e 46 c2 ee b9-0b 75 65 b1 a3 d5 c4 cb .0..F....ue.....
0020 - cf 1f 5f a4 6f 33 1a f5-f6 f5 05 26 c1 3a 37 83 .._.o3.....&.:7.
0030 - 7f e3 0a ec e7 46 10 4f-5c 87 43 c0 a8 fc a5 4c .....F.O\.C....L
0040 - 7e d3 31 fe e0 d2 52 bb-ce 13 a2 ed 64 f4 cc 04 ~.1...R.....d...
0050 - 43 eb 91 1e d2 db bb 2b-e4 ec 83 5a 59 c8 d9 f4 C......+...ZY...
0060 - c2 a4 44 d6 10 f9 e8 24-5c 7b 71 23 7a 31 d3 8e ..D....$\{q#z1..
0070 - 64 b0 35 52 e7 29 bc a7-42 d1 22 4f ee 5b 5b 77 d.5R.)..B."O.[[w
0080 - c5 2b e4 cf 0f 7f 96 74-d6 5f d5 d0 3d 70 c8 76 .+.....t._..=p.v
0090 - d5 00 c3 f4 2b 11 a0 66-83 36 54 94 fc 17 78 48 ....+..f.6T...xH
00a0 - 54 fa 9c 86 7e 91 a7 aa-4a 7b df 56 f6 09 b3 78 T...~...J{.V...x
00b0 - d6 2f 0f 1c 59 79 df 0c-c4 38 11 7e 77 e5 22 e3 ./..Yy...8.~w.".
Start Time: 1730034073
Timeout : 7200 (sec)
Verify return code: 21 (unable to verify the first certificate)
Extended master secret: no
---
closed从输出信息，可以看到Verify return code: 21 (unable to verify the first certificate)，标识客户端验证服务器端的证书时出错了。验证失败以后，客户端主动关闭了连接。
2. ssl验证成功案例
openssl s_client -connect server:443
# openssl s_client -connect www.baidu.com:443
CONNECTED(00000003)
depth=2 OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
verify return:1
depth=1 C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
verify return:1
depth=0 C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
verify return:1
---
Certificate chain
0 s:C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
i:C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
1 s:C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
i:OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
2 s:OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
issuer=C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 5414 bytes and written 437 bytes
Verification: OK
---
New, TLSv1.2, 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: 2D3AA0072F0C633703E65D8C3ADF644C41221A48B57289DBCE04191B000D5288
Session-ID-ctx:
Master-Key: 086B2B73EA1187F084EFF300481A434532BC78FEEBE78DE7BB758EB7F1AC620A42444AE291A20D38E90C5F48C15DE16A
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket:
0000 - a0 fc ac f0 86 15 45 eb-8d 92 e2 0f 16 42 c6 5e ......E......B.^
0010 - c1 db 6b 6a 9d dc 9b 91-12 31 a6 c3 4a e1 48 89 ..kj.....1..J.H.
0020 - 36 60 d6 ff 39 25 07 6b-53 0f 09 66 0a 65 76 77 6`..9%.kS..f.evw
0030 - 4b 2c 22 41 93 7a ed 32-ce d1 36 78 b9 3d ee c6 K,"A.z.2..6x.=..
0040 - ee ee 96 94 5f 89 f5 bd-a0 1a 61 4b 67 ee 59 95 ...._.....aKg.Y.
0050 - e1 33 d3 e3 b8 09 c4 0e-aa b9 79 23 0a c1 53 e3 .3........y#..S.
0060 - 96 ed a4 00 44 ce 29 de-1f 3c 84 ce b1 7f 99 f4 ....D.)..<......
0070 - 32 15 57 32 5e 72 64 e1-1f 3a fa dc a0 35 ec e7 2.W2^rd..:...5..
0080 - 9f 83 39 58 ef 55 97 f2-b0 46 eb 97 6d 6e 71 b3 ..9X.U...F..mnq.
0090 - 47 bb 34 27 37 30 3f 8a-28 11 9d 23 38 24 a9 24 G.4'70?.(..#8$.$
Start Time: 1730034479
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: no
---可以看出，验证结果为：Verify return code: 0 (ok)，表示验证成功。
可以看出成功建立起了ssl连接。
3. 输出证书链
openssl s_client -connect www.baidu.com:443 -showcerts
# openssl s_client -connect www.baidu.com:443 -showcerts
CONNECTED(00000003)
depth=2 OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
verify return:1
depth=1 C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
verify return:1
depth=0 C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
verify return:1
---
Certificate chain
0 s:C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
i:C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
-----BEGIN CERTIFICATE-----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dHJ1c3Rnby5jb22CDyouYmNlLmJhaWR1LmNvbYIQKi5leXVuLmJhaWR1LmNvbYIP
Ki5tYXAuYmFpZHUuY29tgg8qLm1iZC5iYWlkdS5jb22CESouZmFueWkuYmFpZHUu
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Ki5iY2Vob3N0LmNvbYIQKi5zYWZlLmJhaWR1LmNvbYIOKi5pbS5iYWlkdS5jb22C
EiouYmFpZHVjb250ZW50LmNvbYILKi5kbG5lbC5jb22CCyouZGxuZWwub3JnghIq
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-----END CERTIFICATE-----
1 s:C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
i:OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
-----BEGIN CERTIFICATE-----
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hriSqHKvoflShx8xpfywgVcvzfTO3PYkz6fiNJBonf6q8amaEsybwMbDqKWwIX7e
SPY=
-----END CERTIFICATE-----
2 s:OU = GlobalSign Root CA - R3, O = GlobalSign, CN = GlobalSign
i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA
-----BEGIN CERTIFICATE-----
MIIETjCCAzagAwIBAgINAe5fFp3/lzUrZGXWajANBgkqhkiG9w0BAQsFADBXMQsw
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4HA=
-----END CERTIFICATE-----
---
Server certificate
subject=C = CN, ST = beijing, L = beijing, O = "Beijing Baidu Netcom Science Technology Co., Ltd", CN = baidu.com
issuer=C = BE, O = GlobalSign nv-sa, CN = GlobalSign RSA OV SSL CA 2018
---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 5414 bytes and written 437 bytes
Verification: OK
---
New, TLSv1.2, 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: 6512422ADBC7929E785329587F0103448F6FCB6F382ADAE88C8F69DB795EEE77
Session-ID-ctx:
Master-Key: D22D231213A576E6AA1B9C407A1E29851844E20D30D2146D48108959B8D8AF8140D632844B12D2B0631766201C25D97F
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket:
0000 - a0 fc ac f0 86 15 45 eb-8d 92 e2 0f 16 42 c6 5e ......E......B.^
0010 - d8 7f 05 25 be 66 44 ce-c4 1b e5 e2 6c f9 a3 3a ...%.fD.....l..:
0020 - 07 f0 8b c0 69 0f c7 93-b4 6b c1 ef 7a 3e a1 3c ....i....k..z>.<
0030 - 7d d7 2f 68 2a 3d 20 ac-85 02 53 c7 d5 a3 c4 da }./h*= ...S.....
0040 - a2 0a 50 cb b7 73 89 10-3b 7e 44 ed 0d 79 52 1d ..P..s..;~D..yR.
0050 - d7 43 5f f2 c6 e4 33 74-d9 ae b6 88 cf d2 1d 7d .C_...3t.......}
0060 - 93 d3 d4 c9 2b 06 85 20-7e 22 9e 21 d6 b0 7d 7e ....+.. ~".!..}~
0070 - 80 18 4d 5f bc d3 f6 a4-7a b0 bb ff 56 da 6d 0d ..M_....z...V.m.
0080 - 15 cc 29 d0 79 86 e7 e9-2a 11 ed a6 91 60 ac 88 ..).y...*....`..
0090 - 9d 88 80 60 1b 0b b8 fb-16 04 68 34 c9 6a 89 c3 ...`......h4.j..
Start Time: 1730034644
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: no
---4. nginx证书链配置
在nginx中，你需要配置ssl_certificate和ssl_certificate_key，并包含中间证书：
server {
listen 443 ssl;
server_name your.exchange.server;
ssl_certificate /path/to/fullchain.pem; # 包含服务器证书和所有中间证书
ssl_certificate_key /path/to/privatekey.pem;
# 其他配置项
}其中，fullchain.pem应包含完整的证书链，即服务器证书加上所有中间证书。
5. Verify return code: 21的常见原因
Verify return code: 21 (unable to verify the first certificate)
缺少中间证书：服务器未提供完整的证书链，只提供了服务器证书而没有包含必要的中间证书。客户端因此无法验证服务器证书的完整性。
自签名证书：服务器使用了自签名证书，而客户端没有信任该自签名证书。
证书未被信任的证书颁发机构（CA）签发：服务器证书是由一个不被客户端信任的CA签发的。
证书到期或无效：服务器证书已经过期或者在验证过程中被认为无效。
客户端缺少根证书：客户端系统中缺少相应的根证书，无法验证服务器证书链的有效性。