ssl - CSR 的数字签名是如何生成的？

Question

我目前正在学习证书签名请求 (certificates Signing Requests, csr) 的工作原理。我的 csr 的内容是这样的

openssl req -text -noout -verify -in  bobsbooks.com.csr
verify OK
Certificate Request:
Data:
    Version: 0 (0x0)
    Subject: C=UK, ST=Hampshire, L=Southampton, O=Bob's books Ltd, OU=IT Department, CN=bobsbooks.com/emailAddress=admin@bobsbooks.com
    Subject Public Key Info:
        Public Key Algorithm: rsaEncryption
            Public-Key: (2048 bit)
            Modulus:
                00:94:e6:c2:33:ee:e0:67:c9:aa:e8:ff:82:07:40:
                0e:91:ca:19:ea:b2:98:2a:87:b7:1a:ce:c7:d3:3b:
                e3:a9:39:9d:8d:7f:e6:26:84:70:4a:a8:49:97:e9:
                37:72:07:98:58:77:98:03:a7:fd:0f:9e:0d:7f:f6:
                d7:84:ac:40:79:2b:bd:62:18:da:75:f3:e8:5e:33:
                48:82:e4:c2:91:0b:81:74:11:cd:d4:3c:f2:60:f6:
                de:a2:32:97:fd:8c:73:53:6e:fe:33:6c:28:2b:d0:
                e9:9f:af:dc:b3:c6:30:04:bb:e0:e5:41:d8:4b:78:
                b9:0b:53:b2:32:c4:33:62:e0:11:cc:b7:59:26:96:
                95:82:ca:0e:22:37:70:ca:06:9f:1d:27:41:6d:b4:
                64:c6:1b:09:8e:85:72:e0:72:54:1e:eb:ee:d7:54:
                d6:b9:98:99:61:46:1b:1c:da:2d:35:8a:0a:59:bf:
                fe:e9:bd:92:5b:52:74:44:ab:1d:a0:6c:2d:6d:a2:
                6b:d1:ce:ed:ca:ce:a6:0a:d4:4a:14:22:4c:bb:f9:
                1b:e8:8f:74:32:f2:12:4b:6c:54:e4:35:b0:bf:e1:
                3b:83:f0:57:da:55:be:5e:38:03:c2:2c:36:8c:19:
                e0:e5:af:91:67:38:4d:7a:10:04:3d:e2:72:c9:3e:
                eb:ed
            Exponent: 65537 (0x10001)
    Attributes:
        a0:00
Signature Algorithm: sha256WithRSAEncryption
     67:0a:00:b3:62:36:13:e6:c6:ef:04:10:5b:ec:1f:54:fe:55:
     c1:50:30:bc:ca:ae:c6:61:a4:44:9d:98:d5:9b:84:a0:93:60:
     6b:83:02:62:a3:73:96:10:55:f3:90:9e:85:00:22:78:0a:1f:
     45:1c:d0:e6:03:8a:35:72:ce:44:66:08:19:65:44:d7:12:5d:
     00:0a:b9:db:3b:1f:a7:a6:fa:a9:84:f5:3a:61:5f:14:48:89:
     37:37:b4:b0:1f:51:48:2d:02:6b:f4:ff:6b:4d:d3:56:c5:2e:
     43:46:67:6a:cc:be:07:86:b3:82:12:4c:06:67:33:35:5e:63:
     b0:76:33:13:1f:85:70:d9:b6:1e:b3:76:ee:f3:54:40:09:a8:
     60:bc:35:21:cd:1e:bc:bb:49:c8:10:ae:11:03:c9:d2:fa:7c:
     40:9a:53:08:d6:7e:08:9b:be:43:9a:60:79:25:14:7f:5e:6d:
     81:45:2f:39:89:91:3d:8b:8e:3b:84:9c:50:e4:40:88:e1:82:
     cb:5d:3f:af:13:2c:d0:34:3d:c3:e7:35:11:f3:ac:70:1d:b5:
     2e:ae:d6:35:5c:45:75:5c:b5:81:82:a5:c4:73:4e:8a:09:1f:
     5c:44:b7:73:42:d7:68:a0:e2:30:91:4d:29:04:32:e2:1e:bc:
     12:37:74:00

我想弄清楚的是签名 block (签名算法:sha256WithRSAEncryption)是如何生成的。我的理解是，它是公钥的哈希值，已被私钥加密，即:

$ sha256sum bobsbooks.com.public.key | openssl rsautl -inkey bobsbooks.com.private.key -sign | hexdump
0000000 574e 10f5 3a49 5784 25cc 7b06 c234 6ecf
0000010 adb2 9011 9332 e9e7 8dbf 7b10 c7d1 707e
0000020 aaf3 10b1 9497 32a6 d943 5b68 caba 8e5c
0000030 507d 24c7 76bb ab19 d5d7 e653 51e1 f54a
0000040 2a56 7f14 360d 15a9 767b 736a 16bc c3d8
0000050 8cb9 be7a 5ebe 701f 86ef ca5d cfd9 f035
0000060 0b5a 71ac fec4 c5cd 015e 643b 541e 6e5c
0000070 266b 5c33 98d6 db99 2431 d98e d591 04d1
0000080 4479 c85b e180 648b e71c b164 de14 6f33
0000090 fcb1 c2f6 3cc7 61ea 6f0f ab93 a1ad 5ba2
00000a0 af61 addd 4e5e 949e f38b e454 45f7 d12a
00000b0 5dfe 8bc3 b166 e4a0 8075 aa55 2089 49e4
00000c0 1a1d f137 d82b cb47 c0aa 0b14 a897 7879
00000d0 13e2 7c0a 6455 92a6 f9c7 b607 d52b ec07
00000e0 1c66 b9cb d055 ee0b 27b5 fabb 9191 8eb9
00000f0 104c 8ee2 cd81 02b9 d2a9 7502 99bd dbe1
0000100

但是这个输出看起来一点也不像签名。我一定是

Answer 1

解决你的疑惑最好的办法就是引用RFC 2986 - PKCS#10 Certification Request Syntax

CertificationRequest ::= SEQUENCE {

       certificationRequestInfo CertificationRequestInfo,
       signatureAlgorithm AlgorithmIdentifier{{ SignatureAlgorithms }},
       signature          BIT STRING
  }

The signature process consists of two steps:

1. The value of the certificationRequestInfo component is DERencoded, yielding an octet string.

2. The result of step 1 is signed with the certification requestsubject's private key under the specified signaturealgorithm, yielding a bit string, the signature.

所以它签署了整个 CSR，而不仅仅是公钥。