I am new to AWS.How does AES 256 encryption work in s3 bucket?I have uploaded a file in to my s3 bucket and encrypted it with AES 256 Encryption.But i'm able to download the file easily.Is that the expected scenario?It should be asking me to decrypt right?
Yes, thats works as expected. When you enable encryption on S3, it will store data encrypted form at rest. When you download or view files it will decrypt automatically.
Overall idea to encrypt at rest is that if someone steals hardrive from AWS data centre they will not be able to get access to data as it is encrypted.
Related
Encryption max data size allowed for AWS KMS is 4kb, so whenever we use encryption in AWS services/resources is Encryption done using envelope encryption? , i.e, data is encrypted at resource side itself with the key and key is encrypted with another key(cmk)and stored along with the data and decryption happens in the reverse order of above steps. Is my understanding correct??
Probably. It seems to be at least true for S3:
Server-side encryption protects data at rest. Amazon S3 encrypts each object with a unique key. As an additional safeguard, it encrypts the key itself with a master key that it rotates regularly. Amazon S3 server-side encryption uses one of the strongest block ciphers available to encrypt your data, 256-bit Advanced Encryption Standard (AES-256).
Generally the CMK is not used for encrypting the data that you are looking to encrypt.
Whilst it’s a matter of opinion on the 4kb limit, data encryption keys provide a more secure approach to encrypting the data.
Because each resource could have its own data encryption key, the risk is reduced of having all of your resources decrypted if a single encryption key is compromised (in fact if this happens KMS supports re encryption to generate a new data key).
What you describe is correct for S3 implementation of KMS. A Base64 encoded encrypted key is stored alongside the object it encrypts. To decrypt S3 needs to decrypt the data key for the object using the CMK, then use the decrypted data encryption key to decrypt the object.
Other services will have different implementations, for example DynamoDB does this on a per table basis.
For more information on how each service has implemented KMS take a look at the How AWS Services use AWS KMS page
Aws kms does not store any data it provide you two keys
1 plain key : with the help of it you encrypt the data and delete it(key)(no need to save anywhere).
2.encrypted data key :- you need to save this key to decrypt the data( to decrypt the data first you got plain key from aws using encrypted data key) and with the help of plain key you decrypt the data.
Note you need aws kms credentials like :-
a)serviceEndPoint b)awsKeyForKMS c)kmsConfig
KMS Encryption and Decryption in asp.net mvc
Name space need to add from nuget packeg
using Amazon.KeyManagementService;
using Amazon.KeyManagementService.Model;
**1) Encryption :-**
AmazonKeyManagementServiceConfig kmsConfig = new AmazonKeyManagementServiceConfig();
kmsConfig.UseHttp = true;
kmsConfig.ServiceURL = serviceEndPoint;
//create client, specify Region end point or kms config
AmazonKeyManagementServiceClient kmsClient = new AmazonKeyManagementServiceClient(awsKeyForKMS, awsSecretKeyForKMS, kmsConfig);
GenerateDataKeyRequest dataKeyReq = new GenerateDataKeyRequest();
dataKeyReq.KeyId = keyARNForKMS;
dataKeyReq.KeySpec = DataKeySpec.AES_256;//The length of the data encryption key. AES_256 to generate a 256-bit symmetric key.
GenerateDataKeyResponse dataKeyResponse = kmsClient.GenerateDataKey(dataKeyReq);
//read encrypted data key from memory
MemoryStream streamCipherText = dataKeyResponse.CiphertextBlob;
// need to save this key with encrypted data because with the help of it
// you can decrypt(you got plaindatakey) the data
encryptedDataKey = Convert.ToBase64String(streamCipherText.ToArray());
//read plain data key from memory
MemoryStream streamPlainText = dataKeyResponse.Plaintext;
// use this key to encrypt your data and than forgot this key
plainDataKey = Convert.ToBase64String(streamPlainText.ToArray());
//your encryption logic
Encryption encrypt = new Encryption();
encrypt.EncryptTextForKms(PlainKey, "data to be encrypted")
**2.Decryption Data:-**
AmazonKeyManagementServiceConfig kmsConfig = new AmazonKeyManagementServiceConfig();
kmsConfig.UseHttp = true;
kmsConfig.ServiceURL = serviceEndPoint;
//create client, specify Region end point or kms config
AmazonKeyManagementServiceClient kmsClient = new AmazonKeyManagementServiceClient(awsKeyForKMS, awsSecretKeyForKMS, kmsConfig);
DecryptRequest decryptRequest = new DecryptRequest();
// use hare above created encrypteddatakey to get plaindatakey
MemoryStream streamEncryptedDataKey = new MemoryStream(Convert.FromBase64String(encryptedDataKey));//convert to stream object
decryptRequest.CiphertextBlob = streamEncryptedDataKey;
DecryptResponse decryptResp = kmsClient.Decrypt(decryptRequest);
plainDataKey = Convert.ToBase64String(decryptResp.Plaintext.ToArray());
// your decryption logic
DecryptTexts("encrypted data", PlainKey)
One method of ensuring a file in S3 is what it claims to be is to download it, get its checksum, and match the result against the checksum you were expecting.
Does AWS provide any service that allows this to happen without the user needing to first download the file? (i.e. ideally a simple request/url that provides the checksum of an S3 file, so that it can be verified before the file is downloaded)
What I've tried so far
I can think of a DIY solution along the lines of
Create an API endpoint that accepts a POST request with the S3 file url
Have the API run a lambda that generates the checksum of the file
Respond with the checksum value
This may work, but is already a little complicated and would have further considerations, e.g. large files may take a long time to generate a checksum (e.g. > 60 seconds)
I'm hoping AWS have some simple way of validating S3 files?
There is an ETag created against each object, which is an MD5 of the object contents.
However, there seems to be some exceptions.
From Common Response Headers - Amazon Simple Storage Service:
ETag: The entity tag is a hash of the object. The ETag reflects changes only to the contents of an object, not its metadata. The ETag may or may not be an MD5 digest of the object data. Whether or not it is depends on how the object was created and how it is encrypted as described below:
Objects created by the PUT Object, POST Object, or Copy operation, or through the AWS Management Console, and are encrypted by SSE-S3 or plaintext, have ETags that are an MD5 digest of their object data.
Objects created by the PUT Object, POST Object, or Copy operation, or through the AWS Management Console, and are encrypted by SSE-C or SSE-KMS, have ETags that are not an MD5 digest of their object data.
If an object is created by either the Multipart Upload or Part Copy operation, the ETag is not an MD5 digest, regardless of the method of encryption.
Also, the calculation of an ETag for a multi-part upload can be complex. See: s3cmd - What is the algorithm to compute the Amazon-S3 Etag for a file larger than 5GB? - Stack Overflow
Scenario
I have Full text search requirement which can search inside the document. I am uploading documents in s3 bucket and encrypting it using envelope encryption.
Can we do full text search in encrypted document(in S3 bucket). If yes what are the rest API(NodeJS API) for the same.
Example => bucket1 =>Encrypted content in the files
bucket1/abc.pdf
bucket1/def.doc
bucket1/ghi.txt
and I want to search text like "I am from planet earth" in the above files.
I want in result file name(s) with above text.
Solution
I am reading following article:
aws article here
encryption of data at rest
Problem
Will it works if s3 bucket data is encrypted?
What will be the best solution for this scenario?
Elasticsearch does not search inside documents, you need to index the content of the documents inside elasticsearch to be able to perform searchs, it also does not support search on encrypted data, the data needs to be stored in clear text.
What you can do is configure SSL/TLS and authentication on Elasticsearch, so you only will be able to make requests if you use the correct certificate and a username and password.
I have an application running since many time that uploads files (images) on S3 storage.
Now I've been requested to update this application and upload file using SSE-C encryption (Server Side Encryption with Customer provided key). So I did it.
I'm also able to upload SSE-C encrypted files using aws cli.
What I need now, and here is my question, is to find a way to apply SSE-C encryption to earlier files already on S3 without SSE-C encryption.
Could someone explain me if and how this can be accomplished or point me to some doc or support page in order to find a solution?
One (maybe inefficient) way I found is doing the following for each file:
copy filename to filename.encrypted applying the SSE-C encryption
move filename.encrypted to filename
Is this the only way to do it or there is a better one?
NOTES:
Since I have many many files I obviously excluded the option to download the file and then upload again with SSE-C encryption because it'll be too slow and too expensive.
A solution that let apply the SSE-C without data transfert from and back to S3 is the one I'm looking for.
Thank you very much for any feedback on this.
You can apply encryption to already-existing objects by simply copying the object on top of itself:
aws s3 cp s3://bucket/foo.txt s3://bucket/foo.txt --sse-c --sse-c-key fileb://key.bin
This works as long as something (eg the encryption) is changing.
I got the --sse-c syntax from: How to supply a key on the command line that's not Base 64 encoded
I'm using the Amazon Encryption SDK to encrypt data before storing it in a database. I'm also using Amazon KMS. As part of the encryption process, the SDK stores the Key Provider ID of the data key used to encrypt in the generated cipher-text header.
As described in the documentation here http://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/message-format.html#header-structure
The encryption operations in the AWS Encryption SDK return a single
data structure or message that contains the encrypted data
(ciphertext) and all encrypted data keys. To understand this data
structure, or to build libraries that read and write it, you need to
understand the message format.
The message format consists of at least two parts: a header and a
body. In some cases, the message format consists of a third part, a
footer.
The Key Provider ID value contains the Amazon Resource Name (ARN) of the AWS KMS customer master key (CMK).
Here is where the issue comes in. Right now I have two different KMS regions available for encryption. Each Key Provider ID has the exact same Encrypted Data Key value. So either key could be used to decrypt the data. However, the issue is with the ciphertext headers. Let's say I have KMS1 and KMS2. If I encrypt the data with the key provided by KMS1, then the Key Provider ID will be stored in the ciphertext header. If I attempt to decrypt the data with KMS2, even though the Encrypted Data Key is the same, the decryption will fail because the header does not contain the Key Provider for KMS2. It has the Key Provider ID for KMS1. It fails with this error:
com.amazonaws.encryptionsdk.exception.BadCiphertextException: Header integrity check failed.
at com.amazonaws.encryptionsdk.internal.DecryptionHandler.verifyHeaderIntegrity(DecryptionHandler.java:312) ~[application.jar:na]
at com.amazonaws.encryptionsdk.internal.DecryptionHandler.readHeaderFields(DecryptionHandler.java:389) ~[application.jar:na]
...
com.amazonaws.encryptionsdk.internal.DecryptionHandler.verifyHeaderIntegrity(DecryptionHandler.java:310) ~[application.jar:na]
... 16 common frames omitted
Caused by: javax.crypto.AEADBadTagException: Tag mismatch!
It fails to verify the header integrity and fails. This is not good, because I was planning to have multiple KMS's in case of one region KMS failing. We duplicate our data across all our regions, and we thought that we could use any KMS from the regions to decrypt as long as the encrypted data keys match. However, it looks like I'm locked into using only the original KMS that was encrypting the data? How on earth can we scale this to multiple regions if we can only rely on a single KMS?
I could include all the region master keys in the call to encrypt the data. That way, the headers would always match, although it would not reflect which KMS it's actually using. However, that's also not scalable, since we could add/remove regions in the future, and that would cause issues with all the data that's already encrypted.
Am I missing something? I've thought about this, and I want to solve this problem without crippling any integrity checks provided by the SDK/Encryption.
Update:
Based on a comment from #jarmod
Using an alias doesn't work either because we can only associate an alias to a key in the region, and it stores the resolved name of the key ARN it's pointing to anyway.
I'm reading this document and it says
Additionally, envelope encryption can help to design your application
for disaster recovery. You can move your encrypted data as-is between
Regions and only have to reencrypt the data keys with the
Region-specific CMKs
However, that's not accurate at all, because the encryption SDK will fail to decrypt on a different region because the Key Provider ID of the re-encrypted data keys will be totally different!
Apologies since I'm not familiar with Java programming, but I believe there is confusion how you are using the KMS CMKs to encrypt (or decrypt) the data using keys from more than one-region for DR.
When you use multiple master keys to encrypt plaintext, any one of the master keys can be used to decrypt the plaintext. Note that, only one master key (let's say MKey1) generates the plaintext data key which is used to encrypt the data. This plaintext data key is then encrypted by the other master key (MKey2) as well.
As a result, you will have encrypted data + encrypted data key (using MKey1) + encrypted data key (using MKey2).
If for some reason MKey1 is unavailable and you want to decrypt the ciphertext, SDK can be used to decrypt the encrypted data key using MKey2, which can decrypt the ciphertext.
So, yes, you have to specify multiple KMS CMK ARN in your program if you want to use multiple KMS. The document shared by you has an example as well which I'm sure you are aware of.