saas-security-posture

スタートアップ向け SaaS セキュリティ態勢管理

実践的なコマンドベースの強化策で、会社が利用するすべての SaaS ツールを保護します。

1. このスキルを使うタイミング

• SOC 2 の準備 — 監査担当者は MFA、アクセス制御、OAuth ガバナンスの証拠を求めます。
• 不審な OAuth アプリ — 従業員が広範なスコープを持つサードパーティ製アプリを承認しました。
• SaaS の乱立 — チームが会社のメールアドレスでツールに登録し、誰もそれを追跡していません。
• インシデント後の強化 — フィッシングや認証情報の漏えい後に、あらゆる攻撃対象を強化します。

2. SaaS インベントリ監査

Google Workspace — OAuth の許可

gam all users show tokens > oauth_tokens_audit.csv

GitHub — インストール済みアプリ

gh api /orgs/{ORG}/installations --paginate \
  --jq '.installations[] | {app: .app_slug, permissions: .permissions, created: .created_at}'
gh api /orgs/{ORG}/credential-authorizations --paginate \
  --jq '.[] | {login: .login, credential_type: .credential_type}'

Slack — 承認済みおよび保留中のアプリ

curl -s -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  "https://slack.com/api/admin.apps.approved.list" | jq '.approved_apps[] | {name: .app.name, id: .app.id}'
curl -s -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  "https://slack.com/api/admin.apps.requests.list" | jq '.app_requests[]'

AWS — IAM 認証情報レポート

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

インベントリのマスターテンプレート

tools:
  - name: Google Workspace
    owner: [email protected]
    sso: true
    mfa: enforced
  - name: GitHub Enterprise
    owner: [email protected]
    sso: true
    mfa: enforced
  - name: Slack Business+
    owner: [email protected]
    sso: true
    app_approval: required
  - name: AWS Organizations
    owner: [email protected]
    sso: true
    scp_enforced: true

---

3. GitHub のセキュリティ強化

# Enforce 2FA and find non-compliant members
gh api -X PATCH /orgs/{ORG} -f two_factor_requirement_enabled=true
gh api /orgs/{ORG}/members?filter=2fa_disabled --paginate --jq '.[].login'

# Verify SAML SSO identities
gh api /orgs/{ORG}/credential-authorizations --paginate \
  --jq '.[] | {login: .login, saml_name_id: .saml_name_id}'

# Add IP allow list entry
gh api -X POST /orgs/{ORG}/ip-allow-list \
  -f allow_list_value="203.0.113.0/24" -f name="Office VPN" -F is_active=true

# Branch protection on main
gh api -X PUT /repos/{ORG}/{REPO}/branches/main/protection \
  -H "Accept: application/vnd.github+json" --input - <<'EOF'
{
  "required_status_checks": {"strict": true, "contexts": ["ci/build","ci/test"]},
  "enforce_admins": true,
  "required_pull_request_reviews": {
    "required_approving_review_count": 2,
    "dismiss_stale_reviews": true,
    "require_code_owner_reviews": true
  },
  "restrictions": null,
  "allow_force_pushes": false,
  "allow_deletions": false
}
EOF

# Audit PATs and revoke stale tokens
gh api /orgs/{ORG}/personal-access-tokens --paginate \
  --jq '.[] | {owner: .owner.login, name: .token_name, expires: .token_expires_at}'
gh api -X DELETE /orgs/{ORG}/personal-access-tokens/{PAT_ID}

# Audit deploy keys and webhooks
for repo in $(gh repo list {ORG} --limit 500 --json name -q '.[].name'); do
  gh api /repos/{ORG}/${repo}/keys --jq '.[] | {title: .title, read_only: .read_only}'
done
gh api /orgs/{ORG}/hooks --jq '.[] | {url: .config.url, events: .events, active: .active}'

---

4. Slack のセキュリティ

# Require app approval
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.apps.config.set" -d '{"app_approval_enabled": true}'

# Set workspace to invite-only
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.teams.settings.setDiscoverability" \
  -d '{"team_id": "T0XXXXXXX", "discoverability": "invite_only"}'

# Force re-authentication every 24 hours
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.teams.settings.setSessionDuration" \
  -d '{"team_id": "T0XXXXXXX", "session_duration": 86400}'

# Set message retention to 1 year
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.teams.settings.setRetentionPolicy" \
  -d '{"team_id": "T0XXXXXXX", "retention_type": "all", "retention_duration": 365}'

# Audit Slack Connect shared channels
curl -s -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  "https://slack.com/api/admin.conversations.search?search_channel_types=connect" \
  | jq '.conversations[] | {name: .name, is_ext_shared: .is_ext_shared}'

---

5. Google Workspace の強化

# Enforce 2-Step Verification and strong passwords
gam update org "/" settings 2sv enforced
gam update org "/" settings password_length 14

# Block all third-party OAuth apps, then whitelist specific ones
gam update org "/" settings oauth_access block_all
gam update org "/" settings oauth_access whitelist client_id:APP_CLIENT_ID_1

# Disable external Drive sharing and file transfers
gam update org "/" settings drive sharing_outside_domain off
gam update org "/" settings drive transfer_to_personal off
gam update org "/" settings groups external_members off

# Verify email authentication records
dig TXT company.com | grep "v=spf1"
dig TXT google._domainkey.company.com
dig TXT _dmarc.company.com
# Expected: v=DMARC1; p=reject; rua=mailto:[email protected]; pct=100

# Mobile device management
gam update org "/" settings mobile management advanced
gam update org "/" settings mobile screen_lock required
gam update org "/" settings mobile encryption required
gam update mobile ${DEVICE_ID} action wipe   # compromised device

---

6. AWS アカウントのセキュリティ

# Root account lockdown — verify MFA, remove access keys
aws iam get-account-summary --query 'SummaryMap.AccountMFAEnabled'
aws iam get-account-summary --query 'SummaryMap.AccountAccessKeysPresent'

# SSO permission set with least privilege
aws sso-admin create-permission-set --instance-arn "${SSO_INSTANCE_ARN}" \
  --name "DeveloperAccess" --session-duration "PT8H"
aws sso-admin attach-managed-policy-to-permission-set \
  --instance-arn "${SSO_INSTANCE_ARN}" --permission-set-arn "${PERMISSION_SET_ARN}" \
  --managed-policy-arn "arn:aws:iam::aws:policy/ReadOnlyAccess"

サービスコントロールポリシー

{
  "Version": "2012-10-17",
  "Statement": [
    {"Sid": "DenyRootActions", "Effect": "Deny", "Action": "*", "Resource": "*",
     "Condition": {"StringLike": {"aws:PrincipalArn": "arn:aws:iam::*:root"}}},
    {"Sid": "DenyLeaveOrg", "Effect": "Deny",
     "Action": "organizations:LeaveOrganization", "Resource": "*"}
  ]
}

aws organizations create-policy --name "DenyRootActions" \
  --type SERVICE_CONTROL_POLICY --content file://deny-root-actions.json
aws organizations attach-policy --policy-id "${POLICY_ID}" --target-id "${ORG_ROOT_ID}"

# Organization-wide CloudTrail
aws cloudtrail create-trail --name org-security-trail \
  --s3-bucket-name company-cloudtrail-logs \
  --is-multi-region-trail --is-organization-trail --enable-log-file-validation
aws cloudtrail start-logging --name org-security-trail

---

7. OAuth アプリのレビュー

高リスクの許可を特定する

# Google — find apps with dangerous scopes
gam all users show tokens | grep -E "(drive|gmail|admin)" > high_risk_oauth.txt

# GitHub — find apps with write access
gh api /orgs/{ORG}/installations --paginate \
  --jq '.installations[] | select(.permissions.contents == "write") | {app: .app_slug}'

危険な許可を取り消す

gam user [email protected] delete token clientid APP_CLIENT_ID  # single app
gam user [email protected] delete tokens                        # all apps
gh api -X DELETE /orgs/{ORG}/installations/{INSTALLATION_ID}           # GitHub app
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.apps.uninstall" -d '{"app_id": "A0XXXXXXX"}'

スコープのリスク分類

CRITICAL — revoke unless justified:
  Google: mail.google.com, admin.directory.user | GitHub: admin:org, repo | Slack: admin
HIGH — review carefully:
  Google: googleapis.com/auth/drive | GitHub: contents:write | Slack: channels:read
LOW — generally safe:
  Google: userinfo.email | GitHub: read:org | Slack: identity.basic

---

8. 管理者アカウントの保護

# Dedicated admin account in Google Workspace
gam create user [email protected] firstname "John (Admin)" lastname "Doe" \
  password "$(openssl rand -base64 32)" org "/Admins"
gam update user [email protected] admin on

# Require hardware security keys for the Admins OU
gam update org "/Admins" settings 2sv security_key_only

# AWS MFA enforcement policy
cat <<'EOF' > enforce-mfa-policy.json
{
  "Version": "2012-10-17",
  "Statement": [{
    "Sid": "DenyUnlessMFA", "Effect": "Deny",
    "NotAction": ["iam:CreateVirtualMFADevice","iam:EnableMFADevice",
                  "iam:GetUser","iam:ListMFADevices","sts:GetSessionToken"],
    "Resource": "*",
    "Condition": {"BoolIfExists": {"aws:MultiFactorAuthPresent": "false"}}
  }]
}
EOF
aws iam create-policy --policy-name EnforceMFA --policy-document file://enforce-mfa-policy.json

# Break-glass account for SSO outages
BREAK_GLASS_PW=$(openssl rand -base64 48)
gam create user [email protected] firstname "Break" lastname "Glass" \
  password "${BREAK_GLASS_PW}" org "/Admins" admin on
# Store password in a sealed envelope in a physical safe
# After every use: rotate password, re-seal, log the incident

---

9. データ損失防止

# Google Drive — block external sharing and restrict viewers
gam update org "/" settings drive sharing_outside_domain off
gam update org "/" settings drive disable_download_print_copy_for_viewers on

# GitHub — enable secret scanning and push protection org-wide
gh api -X PATCH /orgs/{ORG} -f security_product=secret_scanning -f enablement=enable_all
gh api -X PATCH /orgs/{ORG} -f security_product=secret_scanning_push_protection -f enablement=enable_all
gh api /orgs/{ORG}/secret-scanning/alerts --paginate \
  --jq '.[] | {repo: .repository.name, secret_type: .secret_type, state: .state}'

# Slack — restrict data export to org admins
curl -s -X POST -H "Authorization: Bearer ${SLACK_ADMIN_TOKEN}" \
  -H "Content-Type: application/json" \
  "https://slack.com/api/admin.teams.settings.setExportRestrictions" \
  -d '{"team_id": "T0XXXXXXX", "export_type": "org_admins_only"}'

# AWS — block all public S3 access at account level
aws s3control put-public-access-block --account-id "${AWS_ACCOUNT_ID}" \
  --public-access-block-configuration \
  "BlockPublicAcls=true,IgnorePublicAcls=true,BlockPublicPolicy=true,RestrictPublicBuckets=true"

---

10. シャドー IT の検出

DNS ベースの検出

SHADOW_IT_DOMAINS=("airtable.com" "notion.so" "trello.com" "asana.com"
  "monday.com" "clickup.com" "figma.com" "canva.com" "miro.com"
  "zapier.com" "dropbox.com" "box.com" "wetransfer.com")
for domain in "${SHADOW_IT_DOMAINS[@]}"; do
  count=$(grep -c "${domain}" /var/log/dns/query.log 2>/dev/null || echo "0")
  [ "${count}" -gt 0 ] && echo "DETECTED: ${domain} — ${count} queries"
done

Google Workspace のログイン監査

gam report login parameters app_name \
  start_time "2026-03-01T00:00:00Z" end_time "2026-03-24T23:59:59Z" > login_audit.csv
gam report token > token_usage_report.csv

プロキシログの分析

awk '{print $7}' /var/log/squid/access.log | sed 's|https\?://||;s|/.*||' \
  | sort | uniq -c | sort -rn | head -50 > top_domains.txt
comm -23 <(awk '{print $2}' top_domains.txt | sort) \
  <(yq '.tools[].domains[]' saas-inventory.yaml | sort) > unapproved.txt

アラートの自動化

cat <<'SCRIPT' > /usr/local/bin/shadow-it-check.sh
#!/usr/bin/env bash
set -euo pipefail
APPROVED="/etc/security/approved-saas-domains.txt"
YESTERDAY=$(date -d "yesterday" +%d-%b-%Y)
grep "${YESTERDAY}" /var/log/dns/query.log | awk '{print $4}' | sort -u > /tmp/today.txt
NEW=$(comm -23 /tmp/today.txt <(sort "${APPROVED}"))
[ -n "${NEW}" ] && mail -s "[ALERT] Shadow IT" [email protected] <<< "${NEW}"
SCRIPT
chmod +x /usr/local/bin/shadow-it-check.sh
echo "0 8 * * * root /usr/local/bin/shadow-it-check.sh" >> /etc/cron.d/shadow-it-check

---

クイックリファレンス — 優先度の高い 10 の対策

#	アクション	対象
1	すべてのサービスで MFA/2FA を必須にする	Google、GitHub、AWS、Slack
2	IdP で SSO を有効にする	すべてのツール
3	OAuth の許可を監査して取り消す	Google、GitHub
4	Slack アプリの承認を必須にする	Slack
5	main ブランチの保護を有効にする	GitHub
6	シークレットスキャンとプッシュ保護を有効にする	GitHub
7	S3 バケットの公開をブロックする	AWS
8	組織全体で CloudTrail を有効にする	AWS
9	外部との Drive 共有を無効にする	Google
10	緊急用管理者アカウントを作成する	Google、AWS

メンテナンスの頻度

毎週： OAuth の許可、シークレットスキャンのアラート、Slack アプリのキューを確認します。 毎月： AWS IAM レポートを確認し、サービスキーをローテーションし、管理者アカウントをレビューして、シャドー IT をスキャンします。 四半期ごと： SaaS インベントリ全体を更新し、OAuth の許可を整理し、緊急用アカウントをテストして、SCP を更新します。