配置 kubelet 映象憑證提供程式
Kubernetes v1.26 [stable]
從 Kubernetes v1.20 開始,kubelet 可以使用 exec 外掛動態地檢索容器映象倉庫的憑證。kubelet 和 exec 外掛透過 stdio(stdin、stdout 和 stderr)使用 Kubernetes 版本化 API 進行通訊。這些外掛允許 kubelet 動態請求容器倉庫的憑證,而不是將靜態憑證儲存在磁碟上。例如,外掛可以與本地元資料伺服器通訊,以檢索由 kubelet 拉取的映象的短期憑證。
如果以下任何條件為真,你可能對使用此功能感興趣:
- 需要呼叫雲提供商服務 API 以檢索登錄檔的身份驗證資訊。
- 憑證有效期短,需要頻繁請求新憑證。
- 將登錄檔憑證儲存在磁碟上或 imagePullSecrets 中是不可接受的。
本指南演示瞭如何配置 kubelet 的映象憑證提供程式外掛機制。
用於拉取映象的服務賬號令牌
Kubernetes v1.34 [beta]
(預設啟用:true)從 Kubernetes v1.33 開始,kubelet 可以配置為將繫結到要拉取映象的 Pod 的服務賬號令牌傳送到憑證提供程式外掛。
這允許外掛將令牌換取訪問映象倉庫的憑證。
要啟用此功能,必須在 kubelet 上啟用 `KubeletServiceAccountTokenForCredentialProviders` 特性門控,並且必須在外掛的 `CredentialProviderConfig` 檔案中設定 `tokenAttributes` 欄位。
`tokenAttributes` 欄位包含將傳遞給外掛的服務賬號令牌的資訊,包括令牌的預期受眾以及外掛是否要求 Pod 具有服務賬號。
使用服務賬號令牌憑證可以實現以下用例:
- 避免需要基於 kubelet/節點的身份才能從登錄檔拉取映象。
- 允許工作負載根據其自身的執行時身份拉取映象,而無需長期/持久的 Secret。
準備工作
- 你需要一個具有支援 kubelet 憑證提供程式外掛的節點的 Kubernetes 叢集。此支援在 Kubernetes 1.34 中可用;Kubernetes v1.24 和 v1.25 將此作為 Beta 功能包含在內,預設啟用。
- 如果你正在配置一個需要服務賬號令牌的憑證提供程式外掛,則需要一個具有執行 Kubernetes v1.33 或更高版本的節點的 Kubernetes 叢集,並且在 kubelet 上啟用了 `KubeletServiceAccountTokenForCredentialProviders` 特性門控。
- 一個可工作的憑證提供程式 exec 外掛實現。你可以構建自己的外掛或使用雲提供商提供的外掛。
要檢查版本,請輸入 kubectl version
。
在節點上安裝外掛
憑證提供程式外掛是 kubelet 將執行的可執行二進位制檔案。確保外掛二進位制檔案存在於叢集中的每個節點上,並存儲在已知目錄中。稍後在配置 kubelet 標誌時將需要該目錄。
配置 kubelet
為了使用此功能,kubelet 需要設定兩個標誌:
- `--image-credential-provider-config` - 憑證提供程式外掛配置檔案的路徑。
- `--image-credential-provider-bin-dir` - 憑證提供程式外掛二進位制檔案所在的目錄的路徑。
配置 kubelet 憑證提供程式
傳遞給 `--image-credential-provider-config` 的配置檔案由 kubelet 讀取,以確定哪些容器映象應該呼叫哪些 exec 外掛。如果你正在使用 基於 ECR 的外掛,這有一個你可能最終會使用的配置檔案示例
apiVersion: kubelet.config.k8s.io/v1
kind: CredentialProviderConfig
# providers is a list of credential provider helper plugins that will be enabled by the kubelet.
# Multiple providers may match against a single image, in which case credentials
# from all providers will be returned to the kubelet. If multiple providers are called
# for a single image, the results are combined. If providers return overlapping
# auth keys, the value from the provider earlier in this list is used.
providers:
# name is the required name of the credential provider. It must match the name of the
# provider executable as seen by the kubelet. The executable must be in the kubelet's
# bin directory (set by the --image-credential-provider-bin-dir flag).
- name: ecr-credential-provider
# matchImages is a required list of strings used to match against images in order to
# determine if this provider should be invoked. If one of the strings matches the
# requested image from the kubelet, the plugin will be invoked and given a chance
# to provide credentials. Images are expected to contain the registry domain
# and URL path.
#
# Each entry in matchImages is a pattern which can optionally contain a port and a path.
# Globs can be used in the domain, but not in the port or the path. Globs are supported
# as subdomains like '*.k8s.io' or 'k8s.*.io', and top-level-domains such as 'k8s.*'.
# Matching partial subdomains like 'app*.k8s.io' is also supported. Each glob can only match
# a single subdomain segment, so `*.io` does **not** match `*.k8s.io`.
#
# A match exists between an image and a matchImage when all of the below are true:
# - Both contain the same number of domain parts and each part matches.
# - The URL path of an matchImages must be a prefix of the target image URL path.
# - If the matchImages contains a port, then the port must match in the image as well.
#
# Example values of matchImages:
# - 123456789.dkr.ecr.us-east-1.amazonaws.com
# - *.azurecr.io
# - gcr.io
# - *.*.registry.io
# - registry.io:8080/path
matchImages:
- "*.dkr.ecr.*.amazonaws.com"
- "*.dkr.ecr.*.amazonaws.com.cn"
- "*.dkr.ecr-fips.*.amazonaws.com"
- "*.dkr.ecr.us-iso-east-1.c2s.ic.gov"
- "*.dkr.ecr.us-isob-east-1.sc2s.sgov.gov"
# defaultCacheDuration is the default duration the plugin will cache credentials in-memory
# if a cache duration is not provided in the plugin response. This field is required.
defaultCacheDuration: "12h"
# Required input version of the exec CredentialProviderRequest. The returned CredentialProviderResponse
# MUST use the same encoding version as the input. Current supported values are:
# - credentialprovider.kubelet.k8s.io/v1
apiVersion: credentialprovider.kubelet.k8s.io/v1
# Arguments to pass to the command when executing it.
# +optional
# args:
# - --example-argument
# Env defines additional environment variables to expose to the process. These
# are unioned with the host's environment, as well as variables client-go uses
# to pass argument to the plugin.
# +optional
env:
- name: AWS_PROFILE
value: example_profile
# tokenAttributes is the configuration for the service account token that will be passed to the plugin.
# The credential provider opts in to using service account tokens for image pull by setting this field.
# if this field is set without the `KubeletServiceAccountTokenForCredentialProviders` feature gate enabled,
# kubelet will fail to start with invalid configuration error.
# +optional
tokenAttributes:
# serviceAccountTokenAudience is the intended audience for the projected service account token.
# +required
serviceAccountTokenAudience: "<audience for the token>"
# cacheType indicates the type of cache key use for caching the credentials returned by the plugin
# when the service account token is used.
# The most conservative option is to set this to "Token", which means the kubelet will cache
# returned credentials on a per-token basis. This should be set if the returned credential's
# lifetime is limited to the service account token's lifetime.
# If the plugin's credential retrieval logic depends only on the service account and not on
# pod-specific claims, then the plugin can set this to "ServiceAccount". In this case, the
# kubelet will cache returned credentials on a per-serviceaccount basis. Use this when the
# returned credential is valid for all pods using the same service account.
# +required
cacheType: "<Token or ServiceAccount>"
# requireServiceAccount indicates whether the plugin requires the pod to have a service account.
# If set to true, kubelet will only invoke the plugin if the pod has a service account.
# If set to false, kubelet will invoke the plugin even if the pod does not have a service account
# and will not include a token in the CredentialProviderRequest. This is useful for plugins
# that are used to pull images for pods without service accounts (e.g., static pods).
# +required
requireServiceAccount: true
# requiredServiceAccountAnnotationKeys is the list of annotation keys that the plugin is interested in
# and that are required to be present in the service account.
# The keys defined in this list will be extracted from the corresponding service account and passed
# to the plugin as part of the CredentialProviderRequest. If any of the keys defined in this list
# are not present in the service account, kubelet will not invoke the plugin and will return an error.
# This field is optional and may be empty. Plugins may use this field to extract additional information
# required to fetch credentials or allow workloads to opt in to using service account tokens for image pull.
# If non-empty, requireServiceAccount must be set to true.
# The keys defined in this list must be unique and not overlap with the keys defined in the
# optionalServiceAccountAnnotationKeys list.
# +optional
requiredServiceAccountAnnotationKeys:
- "example.com/required-annotation-key-1"
- "example.com/required-annotation-key-2"
# optionalServiceAccountAnnotationKeys is the list of annotation keys that the plugin is interested in
# and that are optional to be present in the service account.
# The keys defined in this list will be extracted from the corresponding service account and passed
# to the plugin as part of the CredentialProviderRequest. The plugin is responsible for validating the
# existence of annotations and their values. This field is optional and may be empty.
# Plugins may use this field to extract additional information required to fetch credentials.
# The keys defined in this list must be unique and not overlap with the keys defined in the
# requiredServiceAccountAnnotationKeys list.
# +optional
optionalServiceAccountAnnotationKeys:
- "example.com/optional-annotation-key-1"
- "example.com/optional-annotation-key-2"
`providers` 欄位是 kubelet 使用的已啟用外掛列表。每個條目都有幾個必需欄位:
- `name`: 外掛的名稱,必須與傳遞給 `--image-credential-provider-bin-dir` 的目錄中存在的二進位制可執行檔案的名稱匹配。
- `matchImages`: 用於匹配映象以確定是否應呼叫此提供程式的字串列表。詳見下文。
- `defaultCacheDuration`: 如果外掛未指定快取持續時間,kubelet 將在記憶體中快取憑證的預設持續時間。
- `apiVersion`: kubelet 和 exec 外掛在通訊時將使用的 API 版本。
每個憑證提供程式還可以獲得可選的引數和環境變數。請諮詢外掛實現者以確定給定外掛所需的引數和環境變數集。
如果你正在使用 `KubeletServiceAccountTokenForCredentialProviders` 特性門控,並透過設定 `tokenAttributes` 欄位將外掛配置為使用服務賬號令牌,則需要以下欄位:
- `serviceAccountTokenAudience`: 預期投射服務賬號令牌的受眾。這不能是空字串。
- `cacheType`: 當使用服務賬號令牌時,用於快取外掛返回的憑證的快取鍵型別。最保守的選項是將其設定為 `Token`,這意味著 kubelet 將按令牌快取返回的憑證。如果返回的憑證的生命週期限制為服務賬號令牌的生命週期,則應設定此項。如果外掛的憑證檢索邏輯僅依賴於服務賬號而不依賴於 Pod 特定的宣告,則外掛可以將其設定為 `ServiceAccount`。在這種情況下,kubelet 將按服務賬號快取返回的憑證。當返回的憑證對所有使用相同服務賬號的 Pod 都有效時,請使用此項。
- `requireServiceAccount`: 外掛是否要求 Pod 具有服務賬號。
- 如果設定為 `true`,則 kubelet 僅在 Pod 具有服務賬號時才呼叫外掛。
- 如果設定為 `false`,即使 Pod 沒有服務賬號,kubelet 也會呼叫外掛,並且不會在 `CredentialProviderRequest` 中包含令牌。
這對於用於為沒有服務賬號的 Pod(例如靜態 Pod)拉取映象的外掛很有用。
配置映象匹配
kubelet 使用每個憑證提供程式的 `matchImages` 欄位來確定是否應為 Pod 使用的給定映象呼叫外掛。`matchImages` 中的每個條目都是一個映象模式,可以選擇包含埠和路徑。域中可以使用 glob 模式,但不能在埠或路徑中使用。glob 模式支援子域,如 `*.k8s.io` 或 `k8s.*.io`,以及頂級域,如 `k8s.*`。還支援匹配部分子域,如 `app*.k8s.io`。每個 glob 模式只能匹配一個子域段,因此 `*.io` 不匹配 `*.k8s.io`。
當以下所有條件都為真時,映象名稱和 `matchImage` 條目之間存在匹配:
- 兩者包含相同數量的域部分,並且每個部分都匹配。
- 匹配映象的 URL 路徑必須是目標映象 URL 路徑的字首。
- 如果 `matchImages` 包含埠,則映象中的埠也必須匹配。
`matchImages` 模式的一些示例值是:
123456789.dkr.ecr.us-east-1.amazonaws.com
*.azurecr.io
gcr.io
*.*.registry.io
foo.registry.io:8080/path
下一步
- 請閱讀 kubelet 配置 API (v1) 參考 中關於 `CredentialProviderConfig` 的詳細資訊。
- 請閱讀 kubelet 憑證提供程式 API 參考 (v1)。