簽章驗證
Artifact 簽署讓您驗證您擁有的 Artifact 與專案工作流程建立的 Artifact 相同，且未經未授權方（例如中間人攻擊）修改。此驗證提供共同基礎、保證和知識，讓所有各方都參考相同的 Artifact，即位元組集合，無論它是可執行檔、SBOM 或文字檔。
從 Caddy v2.6.0 開始，CI/CD 發布 Artifact 使用 Sigstore 技術簽署，該技術發布包含關於證書頒發對象詳細資訊的證書。您可以從檢查用於簽署您選擇的 Artifact 的證書開始。證書採用 base64 編碼，因此您首先必須對其進行 base64 解碼才能接收 PEM 檔案。在本範例中，我們將使用 caddy_2.6.0_checksums.txt Artifact，並假設為類 Linux 環境。
首先下載與您選擇的 Artifact 相關的 3 個檔案（即 <the artifact>，它是要驗證其附帶簽章和證書的實際 Artifact，<the artifact>.sig，它是 Artifact 的簽章，以及 <the artifact>.pem，它是從 Sigstore 的 Fulcio 根證書衍生的證書）。然後將下載的 .pem 檔案 base64 解碼為 armored 版本。
base64 -d < caddy_2.6.0_checksums.txt.pem > cert.pem現在您可以使用 openssl 命令檢查證書。對我們剛解碼的證書執行 openssl x509 -in cert.pem -text 會顯示以下程式碼片段輸出。
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-----
現在我們有了證書，可以使用 cosign cli 來驗證簽章。我們執行以下命令（請注意它使用未解碼的證書）。
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
現在讓我們切換 cli 工具並使用 rekor-cli，它與儲存透明度日誌的公共 Rekor 伺服器互動。讓我們執行。
rekor-cli get --uuid 04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09 --format json | jq -r '.'
使用 jq 是為了美化輸出。您應該會看到如下輸出。
{
"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"
}
請注意 .Body.HashedRekordObj.signature.content 的值如何與在我們的 CI 中產生且在檔案 caddy_2.6.0_checksums.txt.sig 中可用的簽章內容相符。此外，使用的和下載的證書也儲存在 Rekor 伺服器中，並在回應中的 .Body.HashedRekordObj.signature.publicKey.content 中可用，並與我們在檔案 caddy_2.6.0_checksums.txt.pem 中的字串相符。我們可以更進一步，檢查 .Body.HashedRekordObj.data.hash.value 如何與命令 sha256sum ./caddy_2.6.0_checksums.txt 的輸出相符。因此，到目前為止，我們有相符的證書、相符的簽章和相符的校驗和（包含封存檔校驗和的檔案的校驗和，但不是它自己的校驗和；此校驗和透過 Sigstore 生態系統在外部提供和記錄）。所有這些都公開記錄在透明度日誌中，供一般大眾驗證。
驗證 Artifact 的真實性
如果您收到一個聲稱是 Caddy 專案產品的 Artifact，但您沒有獲得簽章檔案或證書怎麼辦？您可以使用 rekor-cli 向 Rekor 伺服器查詢目標 Artifact。
rekor-cli search --artifact ./caddy_2.6.0_checksums.txt --format json | jq -r '.UUIDs[0]'
Found matching entries (listed by UUID):
362f8ecba72f432604deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09請注意 UUID 如何與先前章節中針對相同檔案遇到的 UUID 相符。就像我們在先前章節中所做的那樣，我們可以向 Rekor 查詢此 UUID 的條目詳細資訊。
rekor-cli get --uuid 04deb84e5a73ba75ea69092c6d700eaeb869c29cae3e0cf98dbfef871361ed09 --format json | jq -r '.'但是，我們可以透過執行此行程式碼將兩個獨立的命令合併為單行程式碼，來縮短查詢時間。
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"
}
我們現在知道 Artifact 已簽署，並且其簽章已記錄在 Rekor 透明度日誌伺服器上。下一步是驗證簽章和 Artifact 是 Caddy 專案 CI/CD 工作流程的產品。我們透過從查詢 Rekor 收到的 JSON 中提取公鑰，將其 base64 解碼為 PEM 檔案，然後使用 openssl 檢查證書來完成此操作。執行以下命令以從我們先前收到的 Rekor 回應中提取證書，將其 base64 解碼，並將結果儲存到檔案中。
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
現在使用 openssl 檢查證書，並注意 X509v3 extensions 區段。
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..
...
擴展值 指示 Artifact 的真實性。請參閱 Sigstore OID 資訊 以取得每個擴展的定義。
如果簽章未驗證怎麼辦？
簽章驗證失敗表示手邊的 Artifact 不是由 GitHub 上 Caddy 專案的 CI/CD 工作流程產生的。如果您有簽章、證書和 Artifact，那麼您正在尋找 cosign 報告的成功驗證。或者，您可以使用 rekor-cli 檢查 Rekor 伺服器中的條目，驗證證書擴展是否具有正確且預期的值，並比對校驗和和簽章。不符或缺少 Rekor 條目表示 Artifact 要么不是由 Caddy 專案的 CI/CD 產生的，要么 Artifact 在 CI/CD 的建置流程、GitHub 發布頁面和交付給您之間被篡改。