fix(core): Verify ec2 instance identity doc before using meta-data service

packages/aws-rfdk/lib/core/lib/mountable-ebs.ts

@@ -187,7 +187,7 @@ export class MountableBlockVolume implements IMountableLinuxFilesystem {
     const uniqueId = 'MountableBlockVolumeAsset' + uuid.replace(/[-]/g, '');
     return (stack.node.tryFindChild(uniqueId) as Asset) ?? new Asset(stack, uniqueId, {
       path: path.join(__dirname, '..', 'scripts', 'bash'),
-      exclude: [ '**/*', '!mountEbsBlockVolume.sh', '!metadataUtilities.sh' ],
+      exclude: [ '**/*', '!mountEbsBlockVolume.sh', '!metadataUtilities.sh', '!ec2-certificates.crt' ],
     });
   }
 }

packages/aws-rfdk/lib/core/lib/mountable-efs.ts

@@ -102,7 +102,7 @@ export class MountableEfs implements IMountableLinuxFilesystem {
     const uniqueId = 'MountableEfsAsset' + uuid.replace(/[-]/g, '');
     return (stack.node.tryFindChild(uniqueId) as Asset) ?? new Asset(stack, uniqueId, {
       path: path.join(__dirname, '..', 'scripts', 'bash'),
-      exclude: [ '**/*', '!mountEfs.sh', '!metadataUtilities.sh' ],
+      exclude: [ '**/*', '!mountEfs.sh', '!metadataUtilities.sh', '!ec2-certificates.crt' ],
     });
   }
 }

packages/aws-rfdk/lib/core/scripts/bash/ec2-certificates.crt

@@ -0,0 +1,92 @@
+-----BEGIN CERTIFICATE-----
+MIIC7TCCAq0CCQCWukjZ5V4aZzAJBgcqhkjOOAQDMFwxCzAJBgNVBAYTAlVTMRkw
+FwYDVQQIExBXYXNoaW5ndG9uIFN0YXRlMRAwDgYDVQQHEwdTZWF0dGxlMSAwHgYD
+VQQKExdBbWF6b24gV2ViIFNlcnZpY2VzIExMQzAeFw0xMjAxMDUxMjU2MTJaFw0z
+ODAxMDUxMjU2MTJaMFwxCzAJBgNVBAYTAlVTMRkwFwYDVQQIExBXYXNoaW5ndG9u
+IFN0YXRlMRAwDgYDVQQHEwdTZWF0dGxlMSAwHgYDVQQKExdBbWF6b24gV2ViIFNl
+cnZpY2VzIExMQzCCAbcwggEsBgcqhkjOOAQBMIIBHwKBgQCjkvcS2bb1VQ4yt/5e
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+7HX32MxXYruse9ACFBNGmdX2ZBrVNGrN9N2f6ROk0k9K
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIC7zCCAq4CCQCO7MJe5Y3VLjAJBgcqhkjOOAQDMFwxCzAJBgNVBAYTAlVTMRkw
+FwYDVQQIExBXYXNoaW5ndG9uIFN0YXRlMRAwDgYDVQQHEwdTZWF0dGxlMSAwHgYD
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+cLoM4p/jtVFOj26xbgIUUS4pDKyHaG/eaygLTtFpFJqzWHc=
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
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+9RyWLHKxH1dMuA==
+-----END CERTIFICATE-----

packages/aws-rfdk/lib/core/scripts/bash/metadataUtilities.sh

@@ -16,6 +16,35 @@ function get_metadata_token() {
     curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 30" 2> /dev/null
 }
 
+function authenticate_identity_document() {
+    # Cryptographically verify that the instance identity document is authentic by
+    # using the instructions here: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/verify-pkcs7.html
+
+    if ! which openssl > /dev/null 2>&1
+    then
+        if ! sudo yum install -y openssl || sudo apt-get install -y openssl
+        then
+            echo "ERROR -- Authenticating the instance identity document requires openssl"
+            return 1
+        fi
+    fi
+
+    SCRIPT_DIRECTORY=$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )
+    TOKEN=$(get_metadata_token)
+
+    CERT_FILE=$(mktemp)
+    echo "-----BEGIN PKCS7-----" > "${CERT_FILE}"
+    curl -H "X-aws-ec2-metadata-token: $TOKEN" -v http://169.254.169.254/latest/dynamic/instance-identity/pkcs7 2> /dev/null >> "${CERT_FILE}"
+    echo "" >> "${CERT_FILE}"
+    echo "-----END PKCS7-----" >> "${CERT_FILE}"
+
+    DOCUMENT_FILE=$(mktemp)
+    curl -H "X-aws-ec2-metadata-token: $TOKEN" -v http://169.254.169.254/latest/dynamic/instance-identity/document 2> /dev/null > "${DOCUMENT_FILE}"
+
+    echo "Verifying identity document authenticity"
+    openssl smime -verify -in "${CERT_FILE}" -inform PEM -content "${DOCUMENT_FILE}" -certfile ${SCRIPT_DIRECTORY}/ec2-certificates.crt -noverify 1> /dev/null
+}
+
 function get_identity_document() {
     # Usage: $0 <token>
     TOKEN=$1

packages/aws-rfdk/lib/core/scripts/bash/mountEbsBlockVolume.sh

@@ -290,6 +290,10 @@ MOUNT_PATH=$3
 MOUNT_OPTIONS=$4
 GIVEN_TARGET_DEVICE=${5:-}
 
+# Make sure that the EC2 instance identity document is authentic before we use it to fetch
+# information about the instance we're running on.
+authenticate_identity_document
+
 # If the EBS volume is already attached, then get the device 
 # name it's attached as.
 TARGET_DEVICE=$(get_attached_device ${VOL_ID})

packages/aws-rfdk/lib/core/scripts/bash/mountEfs.sh

@@ -25,6 +25,10 @@ fi
 SCRIPT_DIR=$(dirname $0)
 source "${SCRIPT_DIR}/metadataUtilities.sh"
 
+# Make sure that the EC2 instance identity document is authentic before we use it to fetch
+# information about the instance we're running on.
+authenticate_identity_document
+
 METADATA_TOKEN=$(get_metadata_token)
 AWS_REGION=$(get_region "${METADATA_TOKEN}")
 

packages/aws-rfdk/lib/core/test/asset-constants.ts

@@ -19,7 +19,7 @@ export const CWA_ASSET_WINDOWS = {
 
 // mountEbsBlockVolume.sh + metadataUtilities.sh
 export const MOUNT_EBS_SCRIPT_LINUX = {
-  Bucket: stringLike('AssetParameters*S3BucketE9BCAE61'),
+  Bucket: stringLike('AssetParameters*S3BucketC33107E6'),
 };
 
 export const INSTALL_MONGODB_3_6_SCRIPT_LINUX = {