签名验证

工件签名允许您验证您拥有的工件与项目工作流程创建的工件相同，并且未被未经授权的方（例如，中间人）修改。验证提供了共同的基础、保证和知识，即所有各方都指的是相同的工件、字节集合，无论它是可执行文件、SBOM 还是文本文件。

从 Caddy v2.6.0 开始，CI/CD 发布工件使用项目 Sigstore 技术进行签名，该技术颁发包含有关证书颁发对象详细信息的证书。您可以首先检查用于签名您选择的工件的证书。证书是 base64 编码的，因此您首先必须对其进行 base64 解码才能接收 PEM 文件。在此示例中，我们将使用 caddy_2.6.0_checksums.txt 工件并假设为类 Linux 环境。

首先下载与您选择的工件相关的 3 个文件（即 <the artifact> 是实际工件，其配套签名和证书将被验证， <the artifact>.sig 是工件的签名，并且 <the artifact>.pem 是由 Sigstore 的 Fulcio 根证书派生的证书）。然后将下载的 .pem 文件 base64 解码为装甲版本

base64 -d < caddy_2.6.0_checksums.txt.pem > cert.pem

您现在可以使用 openssl 命令检查证书。对我们刚刚解码的证书运行 openssl x509 -in cert.pem -text 会显示此代码段输出

openssl x509 -in cert.pem -text
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            22:b0:45:9d:ad:d7:54:98:67:66:b7:de:31:01:ef:4a:02:ab:fb:60
    Signature Algorithm: ecdsa-with-SHA384
        Issuer: O=sigstore.dev, CN=sigstore-intermediate
        Validity
            Not Before: Sep 20 17:17:06 2022 GMT
            Not After : Sep 20 17:27:06 2022 GMT
        Subject:
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)
                pub:
                    04:22:ee:f6:b1:85:1c:de:cf:90:1d:91:75:36:c4:
                    82:9d:54:5e:f3:a6:5b:3f:18:89:8a:0b:de:d8:93:
                    7c:02:40:39:00:d4:4e:19:0b:30:93:cc:a4:d0:df:
                    35:f7:b1:08:24:89:cf:3a:38:06:ff:92:75:06:84:
                    b5:9e:25:8c:9a
                ASN1 OID: prime256v1
                NIST CURVE: P-256
        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature
            X509v3 Extended Key Usage:
                Code Signing
            X509v3 Subject Key Identifier:
                3B:C0:D1:D2:C8:BA:2D:55:95:1F:68:78:DC:C6:2C:D9:B5:17:0E:EA
            X509v3 Authority Key Identifier:
                keyid:DF:D3:E9:CF:56:24:11:96:F9:A8:D8:E9:28:55:A2:C6:2E:18:64:3F

            X509v3 Subject Alternative Name: critical
                URI:https://github.com/caddyserver/caddy/.github/workflows/release.yml@refs/tags/v2.6.0
            1.3.6.1.4.1.57264.1.1:
                https://token.actions.githubusercontent.com
            1.3.6.1.4.1.57264.1.2:
                push
            1.3.6.1.4.1.57264.1.3:
                821a08a6e39ed0e7c43b0271ccf126c194eb6339
            1.3.6.1.4.1.57264.1.4:
                Release
            1.3.6.1.4.1.57264.1.5:
                caddyserver/caddy
            1.3.6.1.4.1.57264.1.6:
                refs/tags/v2.6.0
            1.3.6.1.4.1.11129.2.4.2:
                .z.x.v..`..(R.hE..k'..Eg...=.8.m..".6or....[.DS.....G0E.!..>MD.a..B.p..^..P*...um.....X..F. NYy.....#...TWIZ...y..qa....4P..
    Signature Algorithm: ecdsa-with-SHA384
         30:66:02:31:00:be:b3:3c:15:56:78:64:c6:0f:bc:48:69:a9:
         0a:27:cd:4d:92:39:00:50:42:a8:2a:ad:11:4d:64:f2:61:35:
         ec:08:e9:b5:6a:14:1b:f6:c1:0e:46:ee:a0:54:08:26:e1:02:
         31:00:a7:6d:97:db:4c:c8:dd:47:13:3d:28:7a:a6:f3:64:50:
         2c:5a:9d:9d:10:d0:cf:6f:d0:e9:37:76:fd:cc:8e:9d:c3:6b:
         ba:78:07:40:6a:40:d6:db:f6:97:d5:6a:36:9d
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

现在我们有了证书，我们可以使用 cosign cli 来验证签名。我们运行以下命令（请注意它使用未解码的证书）

COSIGN_EXPERIMENTAL=1 cosign verify-blob --certificate ./caddy_2.6.0_checksums.txt.pem --signature ./caddy_2.6.0_checksums.txt.sig ./caddy_2.6.0_checksums.txt
tlog entry verified with uuid: 04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09 index: 3618623
Verified OK

现在让我们切换 cli 工具并使用 rekor-cli，它与存储透明度日志的公共 Rekor 服务器交互。让我们运行

rekor-cli get --uuid 04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09 --format json | jq -r '.'

使用 jq 是为了美化输出。您应该看到如下输出

{
  "Attestation": "",
  "AttestationType": "",
  "Body": {
    "HashedRekordObj": {
      "data": {
        "hash": {
          "algorithm": "sha256",
          "value": "508f1044ecd9f14c43c6c8986b45b90fc79f25736e2bc85c0911433ce82533f2"
        }
      },
      "signature": {
        "content": "MEUCIHGL2HP5XzcUESTxIk72FS1aNK54LesTfyo+dVhRMeduAiEAnWZDZ5Ur44Y9056vr4to2Fb9FteG53eAFotv3fUZ4h4=",
        "publicKey": {
          "content": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURsRENDQXhtZ0F3SUJBZ0lVSXJCRm5hM1hWSmhuWnJmZU1RSHZTZ0tyKzJBd0NnWUlLb1pJemowRUF3TXcKTnpFVk1CTUdBMVVFQ2hNTWMybG5jM1J2Y21VdVpHVjJNUjR3SEFZRFZRUURFeFZ6YVdkemRHOXlaUzFwYm5SbApjbTFsWkdsaGRHVXdIaGNOTWpJd09USXdNVGN4TnpBMldoY05Nakl3T1RJd01UY3lOekEyV2pBQU1Ga3dFd1lICktvWkl6ajBDQVFZSUtvWkl6ajBEQVFjRFFnQUVJdTcyc1lVYzNzK1FIWkYxTnNTQ25WUmU4NlpiUHhpSmlndmUKMkpOOEFrQTVBTlJPR1Fzd2s4eWswTjgxOTdFSUpJblBPamdHLzVKMUJvUzFuaVdNbXFPQ0FqZ3dnZ0kwTUE0RwpBMVVkRHdFQi93UUVBd0lIZ0RBVEJnTlZIU1VFRERBS0JnZ3JCZ0VGQlFjREF6QWRCZ05WSFE0RUZnUVVPOERSCjBzaTZMVldWSDJoNDNNWXMyYlVYRHVvd0h3WURWUjBqQkJnd0ZvQVUzOVBwejFZa0VaYjVxTmpwS0ZXaXhpNFkKWkQ4d1lRWURWUjBSQVFIL0JGY3dWWVpUYUhSMGNITTZMeTluYVhSb2RXSXVZMjl0TDJOaFpHUjVjMlZ5ZG1WeQpMMk5oWkdSNUx5NW5hWFJvZFdJdmQyOXlhMlpzYjNkekwzSmxiR1ZoYzJVdWVXMXNRSEpsWm5NdmRHRm5jeTkyCk1pNDJMakF3T1FZS0t3WUJCQUdEdnpBQkFRUXJhSFIwY0hNNkx5OTBiMnRsYmk1aFkzUnBiMjV6TG1kcGRHaDEKWW5WelpYSmpiMjUwWlc1MExtTnZiVEFTQmdvckJnRUVBWU8vTUFFQ0JBUndkWE5vTURZR0Npc0dBUVFCZzc4dwpBUU1FS0RneU1XRXdPR0UyWlRNNVpXUXdaVGRqTkROaU1ESTNNV05qWmpFeU5tTXhPVFJsWWpZek16a3dGUVlLCkt3WUJCQUdEdnpBQkJBUUhVbVZzWldGelpUQWZCZ29yQmdFRUFZTy9NQUVGQkJGallXUmtlWE5sY25abGNpOWoKWVdSa2VUQWVCZ29yQmdFRUFZTy9NQUVHQkJCeVpXWnpMM1JoWjNNdmRqSXVOaTR3TUlHS0Jnb3JCZ0VFQWRaNQpBZ1FDQkh3RWVnQjRBSFlBQ0dDUzhDaFMvMmhGMGRGcko0U2NSV2NZckJZOXd6alNiZWE4SWdZMmIzSUFBQUdEClcrZEVVd0FBQkFNQVJ6QkZBaUVBbkQ1TlJLWmhGTGhDSEhESXpWNmJ3VkFxbFlQNmRXMEN3S1dEbzFqem1FWUMKSUU1WmVlSzE0b2k2SSs3ejJWUlhTVnE0L3IxNUdBRnhZYUNNRnJJMFVPampNQW9HQ0NxR1NNNDlCQU1EQTJrQQpNR1lDTVFDK3N6d1ZWbmhreGcrOFNHbXBDaWZOVFpJNUFGQkNxQ3F0RVUxazhtRTE3QWpwdFdvVUcvYkJEa2J1Cm9GUUlKdUVDTVFDbmJaZmJUTWpkUnhNOUtIcW04MlJRTEZxZG5SRFF6Mi9RNlRkMi9jeU9uY05ydW5nSFFHcEEKMXR2Mmw5VnFOcDA9Ci0tLS0tRU5EIENFUlRJRklDQVRFLS0tLS0K"
        }
      }
    }
  },
  "LogIndex": 3618623,
  "IntegratedTime": 1663694226,
  "UUID": "04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09",
  "LogID": "c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d"
}

请注意 .Body.HashedRekordObj.signature.content 的值如何与我们的 CI 中生成的签名内容匹配，并且在文件 caddy_2.6.0_checksums.txt.sig 中可用。此外，使用和下载的证书也存储在 Rekor 服务器中，并在响应中的 .Body.HashedRekordObj.signature.publicKey.content 中可用，并且与我们在文件 caddy_2.6.0_checksums.txt.pem 中的字符串匹配。我们可以更进一步，检查 .Body.HashedRekordObj.data.hash.value 如何与命令 sha256sum ./caddy_2.6.0_checksums.txt 的输出匹配。因此，到目前为止，我们已经有了匹配的证书、匹配的签名和匹配的校验和（包含归档文件校验和的文件的校验和，但不包括其自身的校验和；此校验和通过 Sigstore 生态系统在外部提供和记录）。所有这些都公开记录在透明度日志中，供公众验证。

验证工件的真实性

如果您收到一个声称是 Caddy 项目的产品的工件，但您没有获得签名文件或证书怎么办？您可以使用 rekor-cli 查询 Rekor 服务器以查找主题工件

rekor-cli search --artifact ./caddy_2.6.0_checksums.txt --format json | jq -r '.UUIDs[0]'
Found matching entries (listed by UUID):
362f8ecba72f432604deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09

请注意 UUID 如何与前面部分中针对同一文件遇到的 UUID 匹配。就像我们在前面部分所做的那样，我们可以查询 Rekor 以获取此 UUID 的条目详细信息

rekor-cli get --uuid 04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09 --format json | jq -r '.'

但是，我们可以通过运行此行将两个单独的命令合并为一个单行命令来缩短查找时间

rekor-cli get --uuid $(rekor-cli search --artifact ./caddy_2.6.0_checksums.txt --format json | jq -r '.UUIDs[0]') --format json | jq -r '.'
{
  "Attestation": "",
  "AttestationType": "",
  "Body": {
    "HashedRekordObj": {
      "data": {
        "hash": {
          "algorithm": "sha256",
          "value": "508f1044ecd9f14c43c6c8986b45b90fc79f25736e2bc85c0911433ce82533f2"
        }
      },
      "signature": {
        "content": "MEUCIHGL2HP5XzcUESTxIk72FS1aNK54LesTfyo+dVhRMeduAiEAnWZDZ5Ur44Y9056vr4to2Fb9FteG53eAFotv3fUZ4h4=",
        "publicKey": {
          "content": "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"
        }
      }
    }
  },
  "LogIndex": 3618623,
  "IntegratedTime": 1663694226,
  "UUID": "04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09",
  "LogID": "c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d"
}

我们现在知道该工件已签名，并且其签名已记录在 Rekor 透明度日志服务器上。下一步是验证签名和工件是否是 Caddy 项目的 CI/CD 工作流程的产物。我们通过从查询 Rekor 收到的 JSON 中提取公钥，将其 base64 解码为 PEM 文件，然后使用 openssl 检查证书来完成此操作。运行以下命令以从我们之前收到的 Rekor 响应中提取证书，对其进行 base64 解码，并将结果存储在文件中。

rekor-cli get --uuid $(rekor-cli search --artifact ./caddy_2.6.0_checksums.txt --format json | jq -r '.UUIDs[0]') --format json | jq -r '.Body.HashedRekordObj.signature.publicKey.content' | base64 -d > cert.pem

现在使用 openssl 检查证书，并注意 X509v3 extensions 部分。

openssl x509 -in cert.pem -text
Certificate:
...
        Issuer: O=sigstore.dev, CN=sigstore-intermediate
...
        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature
            X509v3 Extended Key Usage:
                Code Signing
            X509v3 Subject Key Identifier:
                3B:C0:D1:D2:C8:BA:2D:55:95:1F:68:78:DC:C6:2C:D9:B5:17:0E:EA
            X509v3 Authority Key Identifier:
                keyid:DF:D3:E9:CF:56:24:11:96:F9:A8:D8:E9:28:55:A2:C6:2E:18:64:3F

            X509v3 Subject Alternative Name: critical
                URI:https://github.com/caddyserver/caddy/.github/workflows/release.yml@refs/tags/v2.6.0
            1.3.6.1.4.1.57264.1.1:
                https://token.actions.githubusercontent.com
            1.3.6.1.4.1.57264.1.2:
                push
            1.3.6.1.4.1.57264.1.3:
                821a08a6e39ed0e7c43b0271ccf126c194eb6339
            1.3.6.1.4.1.57264.1.4:
                Release
            1.3.6.1.4.1.57264.1.5:
                caddyserver/caddy
            1.3.6.1.4.1.57264.1.6:
                refs/tags/v2.6.0
            1.3.6.1.4.1.11129.2.4.2:
                .z.x.v..`..(R.hE..k'..Eg...=.8.m..".6or....[.DS.....G0E.!..>MD.a..B.p..^..P*...um.....X..F. NYy.....#...TWIZ...y..qa....4P..
   ...

扩展值指示工件的真实性。有关每个扩展的定义，请参阅 Sigstore OID 信息。

如果签名未经验证怎么办？

签名验证失败表示手头的工件不是在 GitHub 上由 Caddy 项目的 CI/CD 工作流程生成的。如果您有签名、证书和工件，那么您正在寻找 cosign 报告的成功验证。或者，您可以使用 rekor-cli 检查 Rekor 服务器的条目，验证证书扩展是否具有正确和期望的值，并匹配校验和和签名。不匹配或缺少 Rekor 条目意味着该工件要么不是由 Caddy 项目的 CI/CD 生成的，要么该工件在 CI/CD 的构建流程、GitHub 发布页面和交付给您之间被篡改。