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Added SHL Decoding Interfaces and Implementations (#2434)
* Added interfaces and utils needed for decoding * Separated decoderImpl into smaller functions and added more tests for readShlUtils * Started implementing tests for decoderImpl * Finished unit tests for ReadSHLinkUtils * Wrote test for SHLinkDecoder * Added comments and cleaned code * More DecoderImpl unit tests added * Ran gradle checks * Removed constructShl function from impl and SHLScanDataInput from Decoder parameters - refactored tests to acommodate this * Changed test names to use backticks to make them more readable * Migrating asserts to the Truth library * Migrated all decoding tests to use Truth library * Added helpful comments to DecoderImpl * Added kdoc to the Decoder interface * Changed Base64 library from java to android - so minSdk can be kept at 24 * Changed Retrofit object variable name to be more descriptive * Extracted common variables in decoderImpl tests * Changed shLinkScanData create function to be inside the companion object and removed public constructors * Improved kdoc in interface * Refactored decodeSHLink to take in passcode and recipient as separate strings - instead of a predefined JSON object * Ran gradle checks * Correct the IPSDocument create function * Added named parameter in IPSDocument create function * Changed tests to use assertThrows and improved decoder tests --------- Co-authored-by: aditya-07 <[email protected]>
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document/src/main/java/com.google.android.fhir.document/decode/ReadSHLinkUtils.kt
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| /* | ||
| * Copyright 2024 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
|
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| package com.google.android.fhir.document.decode | ||
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| import android.util.Base64 | ||
| import com.nimbusds.jose.JWEDecrypter | ||
| import com.nimbusds.jose.JWEObject | ||
| import com.nimbusds.jose.crypto.DirectDecrypter | ||
| import java.io.ByteArrayOutputStream | ||
| import java.util.zip.DataFormatException | ||
| import java.util.zip.Inflater | ||
| import org.json.JSONObject | ||
|
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| object ReadSHLinkUtils { | ||
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| /* Extracts the part of the link after the 'shlink:/' */ | ||
| fun extractUrl(scannedData: String): String { | ||
| if (scannedData.contains("shlink:/")) { | ||
| return scannedData.substringAfterLast("shlink:/") | ||
| } | ||
| throw IllegalArgumentException("Not a valid SHLink") | ||
| } | ||
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|
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| /* Decodes the extracted url from Base64Url to a byte array */ | ||
| fun decodeUrl(extractedUrl: String): ByteArray { | ||
| if (extractedUrl.isEmpty()) { | ||
| throw IllegalArgumentException("Not a valid Base64 encoded string") | ||
| } | ||
| try { | ||
| return Base64.decode(extractedUrl.toByteArray(), Base64.URL_SAFE) | ||
| } catch (err: IllegalArgumentException) { | ||
| throw IllegalArgumentException("Not a valid Base64 encoded string") | ||
| } | ||
| } | ||
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| /* Returns a string of data found in the verifiableCredential field in the given JSON */ | ||
| fun extractVerifiableCredential(jsonString: String): String { | ||
| val jsonObject = JSONObject(jsonString) | ||
| if (jsonObject.has("verifiableCredential")) { | ||
| val verifiableCredentialArray = jsonObject.getJSONArray("verifiableCredential") | ||
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| if (verifiableCredentialArray.length() > 0) { | ||
| // Assuming you want the first item from the array | ||
| return verifiableCredentialArray.getString(0) | ||
| } | ||
| } | ||
| return "" | ||
| } | ||
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| /* Decodes and decompresses the payload in a JWT token */ | ||
| fun decodeAndDecompressPayload(token: String): String { | ||
| try { | ||
| val tokenParts = token.split('.') | ||
| if (tokenParts.size < 2) { | ||
| throw Error("Invalid JWT token passed in") | ||
| } | ||
| val decoded = Base64.decode(tokenParts[1], Base64.URL_SAFE) | ||
| val inflater = Inflater(true) | ||
| inflater.setInput(decoded) | ||
| val initialBufferSize = 100000 | ||
| val decompressedBytes = ByteArrayOutputStream(initialBufferSize) | ||
| val buffer = ByteArray(8192) | ||
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| try { | ||
| while (!inflater.finished()) { | ||
| val length = inflater.inflate(buffer) | ||
| decompressedBytes.write(buffer, 0, length) | ||
| } | ||
| decompressedBytes.close() | ||
| } catch (e: DataFormatException) { | ||
| throw Error("$e.printStackTrace()") | ||
| } | ||
| inflater.end() | ||
| return decompressedBytes.toByteArray().decodeToString() | ||
| } catch (err: Error) { | ||
| throw Error("Invalid JWT token passed in: $err") | ||
| } | ||
| } | ||
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| /* Decodes and decompresses the embedded health data from a JWE token into a string */ | ||
| fun decodeShc(responseBody: String, key: String): String { | ||
| try { | ||
| if (responseBody.isEmpty() or key.isEmpty()) { | ||
| throw IllegalArgumentException("The provided strings should not be empty") | ||
| } | ||
| val jweObject = JWEObject.parse(responseBody) | ||
| val decodedKey: ByteArray = Base64.decode(key, Base64.URL_SAFE) | ||
| val decrypter: JWEDecrypter = DirectDecrypter(decodedKey) | ||
| jweObject.decrypt(decrypter) | ||
| return jweObject.payload.toString() | ||
| } catch (err: Exception) { | ||
| throw Exception("JWE decryption failed: $err") | ||
| } | ||
| } | ||
| } |
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document/src/main/java/com.google.android.fhir.document/decode/SHLinkDecoder.kt
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| /* | ||
| * Copyright 2024 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
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| package com.google.android.fhir.document.decode | ||
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| import com.google.android.fhir.document.IPSDocument | ||
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| /** | ||
| * The [SHLinkDecoder] interface defines a contract for decoding Smart Health Links (SHLs) into | ||
| * [IPSDocument] objects. Implementations of this interface are responsible for decoding and | ||
| * decompressing SHLs, fetching associated health data from external sources, and creating | ||
| * IPSDocument instances. | ||
| * | ||
| * The process of decoding SHLs is outlined in its documentation | ||
| * [SHL Documentation](https://docs.smarthealthit.org/smart-health-links/). | ||
| * | ||
| * ## Example Decoding Process: | ||
| * A SHL is formatted as `[optionalViewer]shlink:/[Base64-Encoded Payload]` (e.g., | ||
| * `shlink:/eyJsYWJ...`). First, extract the portion of the link after 'shlink:/' and decode this to | ||
| * give a SHL Payload. SHL Payloads are structured as: | ||
| * ``` | ||
| * { | ||
| * "url": manifest url, | ||
| * "key": SHL-specific key, | ||
| * "label": "2023-07-12", | ||
| * "flag": "LPU", | ||
| * "exp": expiration time, | ||
| * "v": SHL Protocol Version | ||
| * } | ||
| * ``` | ||
| * | ||
| * The label, flag, exp, and v properties are optional. | ||
| * | ||
| * Send a POST request to the manifest URL with a header of "Content-Type":"application/json" and a | ||
| * body with a "Recipient", a "Passcode" if the "P" flag is present and optionally | ||
| * "embeddedLengthMax":INT. Example request body: | ||
| * | ||
| * ``` | ||
| * { | ||
| * "recipient" : "example_name", | ||
| * "passcode" : "example_passcode" | ||
| * } | ||
| * ``` | ||
| * ``` | ||
| * | ||
| * If the POST request is successful, a list of files is returned. | ||
| * Example response: | ||
| * | ||
| * ``` | ||
| * | ||
| * { "files" : | ||
| * [ { "contentType": "application/smart-health-card", "location":"https://bucket.cloud.example..." }, { "contentType": "application/smart-health-card", "embedded":"eyJhb..." } ] | ||
| * } | ||
| * | ||
| * ``` | ||
| * | ||
| * A file can be one of two types: | ||
| * - Location: If the resource is stored in a location, a single GET request can be made to retrieve the data. | ||
| * - Embedded: If the file type is embedded, the data is a JWE token which can be decoded with the SHL-specific key. | ||
| */ | ||
| interface SHLinkDecoder { | ||
|
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| /** | ||
| * Decodes and decompresses a Smart Health Link (SHL) into an [IPSDocument] object. | ||
| * | ||
| * @param shLink The full Smart Health Link. | ||
| * @param recipient The recipient for the manifest request. | ||
| * @param passcode The passcode for the manifest request (optional, will be null if the P flag is | ||
| * not present in the SHL payload). | ||
| * @return An [IPSDocument] object if decoding is successful, otherwise null. | ||
| */ | ||
| suspend fun decodeSHLinkToDocument( | ||
| shLink: String, | ||
| recipient: String, | ||
| passcode: String?, | ||
| ): IPSDocument? | ||
| } |
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