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Client-Side Encryption

Last updated: 2023-09-13 14:52:34

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Feature Overview

The Go SDK supports client-side encryption. Files can be encrypted before the upload and decrypted during the download. Client-side encryption is suitable for users who store sensitive data.
Client-side encryption supports the following method: KMS-managed keys: Users only need to provide the Customer Master Key ID (CMK ID) of the KMS service to the SDK. This method requires users to enable KMS service. For more information on KMS service, please see Tencent Key Management System.

Supports and Limits

When you copy or migrate encrypted data, note that you should ensure the integrity and accuracy of the cryptographic metadata. If any encrypted data cannot be decoded due to cryptographic metadata loss/corruption caused by your inappropriate maintenance, you shall bear all losses and consequences arising from it.

Encryption for upload

Before each upload, a random symmetric key will be generated, which will be encrypted using the KMS service. KMS will then Base64-encode the key and store it in the object metadata.
During the upload, the file is encrypted in memory using AES256 algorithm.

Decryption for download

Get the necessary encryption information from the metadata of the file, Base64-decode it, and then decrypt it using the KMS or customer managed key to get the encryption key at upload.
Use the resulting key to decrypt the downloaded input stream using AES256.

Sample Request

For the complete sample, please see Client-Side Encryption - Full Demo of KMS Encryption.

Sample 1. Simple upload and download

// Create the original client.
u, _ := url.Parse("https://examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com")
b := &cos.BaseURL{BucketURL: u}
c := cos.NewClient(b, &http.Client{
    Transport: &cos.AuthorizationTransport{
        SecretID: os.Getenv("SECRETID"), // User's SecretId. It is recommended to use a sub-account key, following the principle of least privilege to reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
        SecretKey: os.Getenv("SECRETKEY"),  // User's SecretKey. It is recommended to use a sub-account key to follow the principle of least privilege and reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
    },
})

// Sample 1. Upload an object.
name := "test/example"

// An identifier that determines a unique master encryption key, which also needs to be passed in during decryption.
// During KMS encryption, set it to EncryptionContext. Up to 1,024 characters are supported. If a value is specified in Encrypt, the same value should be passed to Decrypt.
materialDesc := make(map[string]string)
//materialDesc["desc"] = "material information of your master encrypt key"

// Create a KMS client.
kmsclient, _ := coscrypto.NewKMSClient(c.GetCredential(), "ap-guangzhou")
// Create the KMS master encryption key, whose identifier, materialDesc, should correspond to the master encryption key one to one.
kmsID := os.Getenv("KMSID")
masterCipher, _ := coscrypto.CreateMasterKMS(kmsclient, kmsID, materialDesc)
// Create an encryption client.
client := coscrypto.NewCryptoClient(c, masterCipher)

contentLength := 1024*1024*10 + 1
originData := make([]byte, contentLength)
_, err := rand.Read(originData)
f := bytes.NewReader(originData)
// Encrypt data upon upload.
_, err = client.Object.Put(context.Background(), name, f, nil)
log_status(err)

// Decrypt data upon download.
resp, err := client.Object.Get(context.Background(), name, nil)
log_status(err)
defer resp.Body.Close()
decryptedData, _ := ioutil.ReadAll(resp.Body)
if bytes.Compare(decryptedData, originData[rangeStart:rangeEnd+1]) != 0 {
    fmt.Println("Error: encryptedData != originData")
}

Sample 2. Uploading and downloading an object

// Create the original client.
u, _ := url.Parse("https://examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com")
b := &cos.BaseURL{BucketURL: u}
c := cos.NewClient(b, &http.Client{
    Transport: &cos.AuthorizationTransport{
        SecretID: os.Getenv("SECRETID"), // User's SecretId. It is recommended to use a sub-account key, following the principle of least privilege to reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
        SecretKey: os.Getenv("SECRETKEY"),  // User's SecretKey. It is recommended to use a sub-account key to follow the principle of least privilege and reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
    },
})

// Sample 1. Upload an object.
name := "test/example"

// An identifier that determines a unique master encryption key, which also needs to be passed in during decryption.
// During KMS encryption, set it to EncryptionContext. Up to 1,024 characters are supported. If a value is specified in Encrypt, the same value should be passed to Decrypt.
materialDesc := make(map[string]string)
//materialDesc["desc"] = "material information of your master encrypt key"

// Create a KMS client.
kmsclient, _ := coscrypto.NewKMSClient(c.GetCredential(), "ap-guangzhou")
// Create the KMS master encryption key, whose identifier, materialDesc, should correspond to the master encryption key one to one.
kmsID := os.Getenv("KMSID")
masterCipher, _ := coscrypto.CreateMasterKMS(kmsclient, kmsID, materialDesc)
// Create an encryption client.
client := coscrypto.NewCryptoClient(c, masterCipher)

// Encrypt data upon upload.
_, err = client.Object.PutFromFile(context.Background(), name, filepath, nil)
if err != nil {
    // ERROR
}

// Decrypt data upon download.
_, err = client.Object.GetToFile(context.Background(), name, "./test.download", nil)
if err != nil {
    // ERROR
}

Sample 3. Multipart upload

// Create the original client.
u, _ := url.Parse("https://examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com")
b := &cos.BaseURL{BucketURL: u}
c := cos.NewClient(b, &http.Client{
    Transport: &cos.AuthorizationTransport{
        SecretID: os.Getenv("SECRETID"), // User's SecretId. It is recommended to use a sub-account key, following the principle of least privilege to reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
        SecretKey: os.Getenv("SECRETKEY"),  // User's SecretKey. It is recommended to use a sub-account key to follow the principle of least privilege and reduce usage risks. For obtaining a sub-account key, please refer to https://cloud.tencent.com/document/product/598/37140
    },
})

// Sample 1. Upload an object.
name := "test/example"

// An identifier that determines a unique master encryption key, which also needs to be passed in during decryption.
// During KMS encryption, set it to EncryptionContext. Up to 1,024 characters are supported. If a value is specified in Encrypt, the same value should be passed to Decrypt.
materialDesc := make(map[string]string)
//materialDesc["desc"] = "material information of your master encrypt key"

// Create a KMS client.
kmsclient, _ := coscrypto.NewKMSClient(c.GetCredential(), "ap-guangzhou")
// Create the KMS master encryption key, whose identifier, materialDesc, should correspond to the master encryption key one to one.
kmsID := os.Getenv("KMSID")
masterCipher, _ := coscrypto.CreateMasterKMS(kmsclient, kmsID, materialDesc)
// Create an encryption client.
client := coscrypto.NewCryptoClient(c, masterCipher)

filepath := "test"
stat, err := os.Stat(filepath)
if err !- nil {
    // ERROR
}
contentLength := stat.Size()

// Upload parts.
// Each part should be aligned to 16 bytes and not smaller than 1 MB.
partSize := (contentLength / 16 / 3) * 16
if partSize < int64(1024*1024) {
    partSize = int64(1024*1024)
}
cryptoCtx := coscrypto.CryptoContext{
    DataSize: contentLength,
    // Each block requires 16-byte alignment
    PartSize: partSize,
}
// Split the data.
_, chunks, _, err := cos.SplitFileIntoChunks(filepath, cryptoCtx.PartSize)
if err !- nil {
    // ERROR
}

// init mulitupload
v, _, err := client.Object.InitiateMultipartUpload(context.Background(), name, nil, &cryptoCtx)
if err !- nil {
    // ERROR
}

// part upload
optcom := &cos.CompleteMultipartUploadOptions{}
for _, chunk := range chunks {
    fd, err := os.Open(filepath)
    if err !- nil {
        // ERROR
    }        
    opt := &cos.ObjectUploadPartOptions{
        ContentLength: chunk.Size,
    }
    fd.Seek(chunk.OffSet, os.SEEK_SET)
    resp, err := client.Object.UploadPart(context.Background(), name, v.UploadID, chunk.Number, cos.LimitReadCloser(fd, chunk.Size), opt, &cryptoCtx)
    if err !- nil {
        // ERROR
    }
    optcom.Parts = append(optcom.Parts, cos.Object{
        PartNumber: chunk.Number, ETag: resp.Header.Get("ETag"),
    })
}
// complete upload
_, _, err = client.Object.CompleteMultipartUpload(context.Background(), name, v.UploadID, optcom)
if err !- nil {
    // ERROR
}

_, err = client.Object.GetToFile(context.Background(), name, "test.download", nil)
if err !- nil {
    // ERROR
}

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