aws-iam

AWS IAM

使用权限最小化策略、角色、联合身份验证和权限边界管理 AWS 中的身份与访问权限。

何时使用此技能

• 为 EC2 实例、Lambda 函数或 ECS 任务创建角色
• 编写具有最小权限访问能力的自定义 IAM 策略
• 为 GitHub Actions 或其他 CI/CD 系统设置 OIDC 联合身份验证
• 为委派管理实施权限边界
• 使用 IAM Access Analyzer 和凭证报告审计访问权限
• 使用 AssumeRole 模式配置跨账户访问
• 强制实施 MFA 和会话策略

前提条件

• 已安装并配置 AWS CLI v2
• IAM 权限：iam:*（或按最小权限原则限定为特定操作）
• 对于 OIDC：能够创建身份提供商（iam:CreateOpenIDConnectProvider）
• 拥有 AWS Organizations 访问权限，以使用服务控制策略（SCP）

IAM 策略结构

每个 IAM 策略都遵循相同的 JSON 结构。始终只指定所需的最少操作和资源。

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowS3ReadWrite",
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:PutObject",
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::my-app-bucket",
        "arn:aws:s3:::my-app-bucket/*"
      ],
      "Condition": {
        "StringEquals": {
          "s3:x-amz-server-side-encryption": "aws:kms"
        }
      }
    },
    {
      "Sid": "DenyUnencryptedUploads",
      "Effect": "Deny",
      "Action": "s3:PutObject",
      "Resource": "arn:aws:s3:::my-app-bucket/*",
      "Condition": {
        "StringNotEquals": {
          "s3:x-amz-server-side-encryption": "aws:kms"
        }
      }
    }
  ]
}

创建和管理角色

# Create an EC2 instance role with trust policy
aws iam create-role \
  --role-name EC2AppRole \
  --assume-role-policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Principal": {"Service": "ec2.amazonaws.com"},
      "Action": "sts:AssumeRole"
    }]
  }' \
  --tags '[{"Key":"Team","Value":"platform"},{"Key":"Environment","Value":"production"}]'

# Create and attach an inline policy
aws iam put-role-policy \
  --role-name EC2AppRole \
  --policy-name s3-access \
  --policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Action": ["s3:GetObject", "s3:PutObject"],
      "Resource": "arn:aws:s3:::my-app-bucket/*"
    }]
  }'

# Attach a managed policy
aws iam attach-role-policy \
  --role-name EC2AppRole \
  --policy-arn arn:aws:iam::aws:policy/CloudWatchAgentServerPolicy

# Create instance profile and associate the role
aws iam create-instance-profile --instance-profile-name EC2AppProfile
aws iam add-role-to-instance-profile \
  --instance-profile-name EC2AppProfile \
  --role-name EC2AppRole

# Create a Lambda execution role
aws iam create-role \
  --role-name LambdaExecRole \
  --assume-role-policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Principal": {"Service": "lambda.amazonaws.com"},
      "Action": "sts:AssumeRole"
    }]
  }'

aws iam attach-role-policy \
  --role-name LambdaExecRole \
  --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

跨账户访问

# In Account B: create role that Account A can assume
aws iam create-role \
  --role-name CrossAccountReadRole \
  --assume-role-policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::111111111111:root"},
      "Action": "sts:AssumeRole",
      "Condition": {
        "StringEquals": {"sts:ExternalId": "unique-external-id-12345"}
      }
    }]
  }'

# In Account A: assume the role
aws sts assume-role \
  --role-arn arn:aws:iam::222222222222:role/CrossAccountReadRole \
  --role-session-name cross-account-session \
  --external-id unique-external-id-12345

# Use the temporary credentials
export AWS_ACCESS_KEY_ID="ASIAXXX"
export AWS_SECRET_ACCESS_KEY="xxx"
export AWS_SESSION_TOKEN="xxx"

GitHub Actions 的 OIDC 联合身份验证

# Create the GitHub OIDC identity provider
aws iam create-open-id-connect-provider \
  --url https://token.actions.githubusercontent.com \
  --client-id-list sts.amazonaws.com \
  --thumbprint-list "6938fd4d98bab03faadb97b34396831e3780aea1"

# Create a role for GitHub Actions with repo-scoped trust
aws iam create-role \
  --role-name GitHubActionsDeployRole \
  --assume-role-policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::123456789012:oidc-provider/token.actions.githubusercontent.com"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "token.actions.githubusercontent.com:aud": "sts.amazonaws.com"
        },
        "StringLike": {
          "token.actions.githubusercontent.com:sub": "repo:my-org/my-repo:ref:refs/heads/main"
        }
      }
    }]
  }'

# Attach deployment permissions to the role
aws iam attach-role-policy \
  --role-name GitHubActionsDeployRole \
  --policy-arn arn:aws:iam::123456789012:policy/DeploymentPolicy

GitHub Actions 工作流用法：

# .github/workflows/deploy.yml
permissions:
  id-token: write
  contents: read

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::123456789012:role/GitHubActionsDeployRole
          aws-region: us-east-1
      - run: aws sts get-caller-identity

权限边界

# Create a permission boundary policy
aws iam create-policy \
  --policy-name DeveloperBoundary \
  --policy-document '{
    "Version": "2012-10-17",
    "Statement": [
      {
        "Sid": "AllowedServices",
        "Effect": "Allow",
        "Action": [
          "s3:*",
          "lambda:*",
          "dynamodb:*",
          "sqs:*",
          "sns:*",
          "logs:*",
          "cloudwatch:*",
          "ecr:*",
          "ecs:*"
        ],
        "Resource": "*"
      },
      {
        "Sid": "DenyIAMChanges",
        "Effect": "Deny",
        "Action": [
          "iam:CreateUser",
          "iam:DeleteUser",
          "iam:CreateRole",
          "iam:DeleteRole",
          "iam:AttachRolePolicy",
          "iam:PutRolePermissionsBoundary",
          "iam:DeleteRolePermissionsBoundary"
        ],
        "Resource": "*"
      },
      {
        "Sid": "DenyOutsideRegion",
        "Effect": "Deny",
        "Action": "*",
        "Resource": "*",
        "Condition": {
          "StringNotEquals": {
            "aws:RequestedRegion": ["us-east-1", "us-west-2"]
          },
          "ForAnyValue:StringNotLike": {
            "aws:PrincipalArn": "arn:aws:iam::*:role/admin-*"
          }
        }
      }
    ]
  }'

# Create a role with the permission boundary
aws iam create-role \
  --role-name DeveloperRole \
  --assume-role-policy-document file://trust-policy.json \
  --permissions-boundary "arn:aws:iam::123456789012:policy/DeveloperBoundary"

IAM Access Analyzer 和审计

# Create an IAM Access Analyzer
aws accessanalyzer create-analyzer \
  --analyzer-name account-analyzer \
  --type ACCOUNT

# List findings (externally accessible resources)
aws accessanalyzer list-findings \
  --analyzer-arn arn:aws:access-analyzer:us-east-1:123456789012:analyzer/account-analyzer

# Generate credential report
aws iam generate-credential-report
aws iam get-credential-report --output text --query Content | base64 -d > credential-report.csv

# Find users with console access but no MFA
aws iam list-users --query "Users[].UserName" --output text | while read user; do
  mfa=$(aws iam list-mfa-devices --user-name "$user" --query "MFADevices" --output text)
  if [ -z "$mfa" ]; then
    echo "NO MFA: $user"
  fi
done

# List all policies attached to a role
aws iam list-attached-role-policies --role-name EC2AppRole
aws iam list-role-policies --role-name EC2AppRole

# Get the last-accessed services for a role
aws iam generate-service-last-accessed-details --arn arn:aws:iam::123456789012:role/EC2AppRole
# Then retrieve results with the returned JobId
aws iam get-service-last-accessed-details --job-id "job-id-from-above"

# Simulate a policy to test access
aws iam simulate-principal-policy \
  --policy-source-arn arn:aws:iam::123456789012:role/EC2AppRole \
  --action-names s3:GetObject s3:PutObject \
  --resource-arns arn:aws:s3:::my-app-bucket/data.json

使用 OIDC 的 Terraform IAM 角色

# OIDC provider for GitHub Actions
resource "aws_iam_openid_connect_provider" "github" {
  url             = "https://token.actions.githubusercontent.com"
  client_id_list  = ["sts.amazonaws.com"]
  thumbprint_list = ["6938fd4d98bab03faadb97b34396831e3780aea1"]
}

# Role for GitHub Actions
resource "aws_iam_role" "github_actions" {
  name = "GitHubActionsDeployRole"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Effect = "Allow"
      Principal = {
        Federated = aws_iam_openid_connect_provider.github.arn
      }
      Action = "sts:AssumeRoleWithWebIdentity"
      Condition = {
        StringEquals = {
          "token.actions.githubusercontent.com:aud" = "sts.amazonaws.com"
        }
        StringLike = {
          "token.actions.githubusercontent.com:sub" = "repo:my-org/my-repo:*"
        }
      }
    }]
  })

  permissions_boundary = aws_iam_policy.boundary.arn
}

resource "aws_iam_role_policy_attachment" "deploy" {
  role       = aws_iam_role.github_actions.name
  policy_arn = aws_iam_policy.deployment.arn
}

# Permission boundary
resource "aws_iam_policy" "boundary" {
  name = "DeveloperBoundary"
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Sid      = "AllowedServices"
        Effect   = "Allow"
        Action   = ["s3:*", "lambda:*", "dynamodb:*", "ecs:*", "logs:*"]
        Resource = "*"
      },
      {
        Sid      = "DenyIAMEscalation"
        Effect   = "Deny"
        Action   = ["iam:CreateUser", "iam:CreateRole", "iam:AttachRolePolicy"]
        Resource = "*"
      }
    ]
  })
}

服务控制策略（Organizations）

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "DenyRootAccount",
      "Effect": "Deny",
      "Action": "*",
      "Resource": "*",
      "Condition": {
        "StringLike": {
          "aws:PrincipalArn": "arn:aws:iam::*:root"
        }
      }
    },
    {
      "Sid": "RequireIMDSv2",
      "Effect": "Deny",
      "Action": "ec2:RunInstances",
      "Resource": "arn:aws:ec2:*:*:instance/*",
      "Condition": {
        "StringNotEquals": {
          "ec2:MetadataHttpTokens": "required"
        }
      }
    },
    {
      "Sid": "DenyRegionsOutsideUS",
      "Effect": "Deny",
      "Action": "*",
      "Resource": "*",
      "Condition": {
        "StringNotEquals": {
          "aws:RequestedRegion": ["us-east-1", "us-west-2"]
        },
        "ForAnyValue:StringNotLike": {
          "aws:PrincipalArn": ["arn:aws:iam::*:role/OrganizationAdmin"]
        }
      }
    }
  ]
}

故障排除

问题	原因	解决方法
API 调用时被拒绝访问	缺少策略或策略不正确	使用 simulate-principal-policy 进行测试；检查资源 ARN 格式
无法代入角色	信任策略中未包含调用方	确认信任策略中的 Principal 与调用方 ARN 相符
OIDC 联合身份验证失败	指纹或受众不匹配	确认 OIDC 提供商 URL、客户端 ID 列表和条件键
权限边界阻止操作	边界中未包含该操作	将该操作添加到边界；有效权限 = 身份策略 AND 边界
凭证报告显示密钥过期未轮换	密钥超过 90 天未轮换	轮换密钥；禁用未使用的访问密钥
创建服务关联角色失败	组织 SCP 阻止了 iam:CreateServiceLinkedRole	在 SCP 中为特定服务添加例外
跨账户代入角色失败	缺少 ExternalId 或账户不正确	确认 ExternalId 匹配；检查 Principal 中的账户编号
未强制执行 MFA 条件	策略中没有条件键	添加 aws:MultiFactorAuthPresent 条件

相关技能

• terraform-aws - IAM 资源的 IaC 部署
• aws-ec2 - 实例配置文件和角色
• aws-lambda - Lambda 执行角色
• aws-ecs-fargate - ECS 任务角色和执行角色
• access-review - 访问审计与治理