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88 lines
2.5 KiB
88 lines
2.5 KiB
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build !ts_omit_aws
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// Package awsparamstore registers support for fetching secret values from AWS
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// Parameter Store.
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package awsparamstore
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import (
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"context"
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"fmt"
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"strings"
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"github.com/aws/aws-sdk-go-v2/aws"
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"github.com/aws/aws-sdk-go-v2/aws/arn"
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"github.com/aws/aws-sdk-go-v2/config"
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"github.com/aws/aws-sdk-go-v2/service/ssm"
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"tailscale.com/feature"
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"tailscale.com/internal/client/tailscale"
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)
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func init() {
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feature.Register("awsparamstore")
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tailscale.HookResolveValueFromParameterStore.Set(ResolveValue)
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}
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// parseARN parses and verifies that the input string is an
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// ARN for AWS Parameter Store, returning the region and parameter name if so.
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//
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// If the input is not a valid Parameter Store ARN, it returns ok==false.
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func parseARN(s string) (region, parameterName string, ok bool) {
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parsed, err := arn.Parse(s)
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if err != nil {
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return "", "", false
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}
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if parsed.Service != "ssm" {
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return "", "", false
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}
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parameterName, ok = strings.CutPrefix(parsed.Resource, "parameter/")
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if !ok {
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return "", "", false
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}
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// NOTE: parameter names must have a leading slash
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return parsed.Region, "/" + parameterName, true
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}
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// ResolveValue fetches a value from AWS Parameter Store if the input
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// looks like an SSM ARN (e.g., arn:aws:ssm:us-east-1:123456789012:parameter/my-secret).
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//
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// If the input is not a Parameter Store ARN, it returns the value unchanged.
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//
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// If the input is a Parameter Store ARN and fetching the parameter fails, it
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// returns an error.
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func ResolveValue(ctx context.Context, valueOrARN string) (string, error) {
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// If it doesn't look like an ARN, return as-is
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region, parameterName, ok := parseARN(valueOrARN)
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if !ok {
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return valueOrARN, nil
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}
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// Load AWS config with the region from the ARN
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cfg, err := config.LoadDefaultConfig(ctx, config.WithRegion(region))
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if err != nil {
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return "", fmt.Errorf("loading AWS config in region %q: %w", region, err)
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}
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// Create SSM client and fetch the parameter
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client := ssm.NewFromConfig(cfg)
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output, err := client.GetParameter(ctx, &ssm.GetParameterInput{
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// The parameter to fetch.
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Name: aws.String(parameterName),
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// If the parameter is a SecureString, decrypt it.
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WithDecryption: aws.Bool(true),
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})
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if err != nil {
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return "", fmt.Errorf("getting SSM parameter %q: %w", parameterName, err)
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}
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if output.Parameter == nil || output.Parameter.Value == nil {
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return "", fmt.Errorf("SSM parameter %q has no value", parameterName)
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}
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return strings.TrimSpace(*output.Parameter.Value), nil
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}
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