VS Code中Azure Function报错：inputStream应位于流起始位置

我开发了一个Blob触发的Azure Function，功能是对入站容器接收的文件进行PGP加密，再将加密后的文件放入出站容器。该函数在Visual Studio 2022本地运行正常，但在VS Code中复制相同代码后，抛出错误：

inputStream should be at start of stream.

函数代码：

using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using Azure.Identity;
using Azure.Security.KeyVault.Secrets;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using PgpCore;

public class Function1
{
    private readonly string keyVaultName = "MyKV";
    private readonly string keyName = "SKEY";
    private readonly string outboundContainerName = "OutBound";

    [FunctionName("BlobTriggerFunction")]
    public async Task Run(
        [BlobTrigger("Inbound/{name}.txt", Connection = "Devsandpit")] Stream inblobStream,
        string name,
        ILogger log)
    {
        log.LogInformation($"C# Blob trigger function Processed blob\n Name:{name} \n Size: {inblobStream.Length} Bytes");

        // Get PGP public key from Azure Key Vault
        var client = new SecretClient(new Uri($"https://{keyVaultName}.vault.azure.net/"), new DefaultAzureCredential());
        KeyVaultSecret secret = await client.GetSecretAsync(keyName);
        string publicKey = secret.Value;

        // Decode the Base64 encoded public key
        byte[] publicKeyBytes = Convert.FromBase64String(publicKey);

        // Using MemoryStream for the public key
        using (MemoryStream publicKeyStream = new MemoryStream(publicKeyBytes))
        using (Stream outputFileStream = new MemoryStream())
        {
            // Initialize PGP encryption keys and PGP utility
            EncryptionKeys encryptionKeys = new EncryptionKeys(publicKeyStream);
            PGP pgp = new PGP(encryptionKeys);

            // Prepare the input data for encryption
            MemoryStream memoryStream = new MemoryStream();
            await inblobStream.CopyToAsync(memoryStream);
            memoryStream.Position = 0;
            
            // Encrypt the data stream
            await pgp.EncryptStreamAsync(inblobStream, outputFileStream);
            outputFileStream.Position = 0;

            // Upload encrypted file to outbound container
            BlobServiceClient blobServiceClient = new BlobServiceClient(Environment.GetEnvironmentVariable("Devsandpit"));
            BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(outboundContainerName);
            BlobClient blobClient = containerClient.GetBlobClient(name);

            await blobClient.UploadAsync(outputFileStream, new BlobHttpHeaders { ContentType = "application/octet-stream" });
        }
    }
}

解决方案 #

问题根源 #

你已经将inblobStream的内容复制到memoryStream并重置了位置，但加密时却传入了读取到末尾的inblobStream——流被读取后，位置指针会移动到流的末尾，此时PGP加密方法无法读取任何数据，触发"inputStream should be at start of stream"错误。

修改方案 #

直接使用你已经准备好的memoryStream作为加密输入（推荐此方案，彻底规避流位置问题）：

修改后的代码：

using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using Azure.Identity;
using Azure.Security.KeyVault.Secrets;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using PgpCore;

public class Function1
{
    private readonly string keyVaultName = "MyKV";
    private readonly string keyName = "SKEY";
    private readonly string outboundContainerName = "OutBound";

    [FunctionName("BlobTriggerFunction")]
    public async Task Run(
        [BlobTrigger("Inbound/{name}.txt", Connection = "Devsandpit")] Stream inblobStream,
        string name,
        ILogger log)
    {
        log.LogInformation($"C# Blob trigger function Processed blob\n Name:{name} \n Size: {inblobStream.Length} Bytes");

        // Get PGP public key from Azure Key Vault
        var client = new SecretClient(new Uri($"https://{keyVaultName}.vault.azure.net/"), new DefaultAzureCredential());
        KeyVaultSecret secret = await client.GetSecretAsync(keyName);
        string publicKey = secret.Value;

        // Decode the Base64 encoded public key
        byte[] publicKeyBytes = Convert.FromBase64String(publicKey);

        // Using MemoryStream for the public key
        using (MemoryStream publicKeyStream = new MemoryStream(publicKeyBytes))
        using (Stream outputFileStream = new MemoryStream())
        {
            // Initialize PGP encryption keys and PGP utility
            EncryptionKeys encryptionKeys = new EncryptionKeys(publicKeyStream);
            PGP pgp = new PGP(encryptionKeys);

            // Prepare the input data for encryption
            MemoryStream memoryStream = new MemoryStream();
            await inblobStream.CopyToAsync(memoryStream);
            memoryStream.Position = 0;
            
            // 修改：使用已重置位置的memoryStream作为加密输入
            await pgp.EncryptStreamAsync(memoryStream, outputFileStream);
            outputFileStream.Position = 0;

            // Upload encrypted file to outbound container
            BlobServiceClient blobServiceClient = new BlobServiceClient(Environment.GetEnvironmentVariable("Devsandpit"));
            BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(outboundContainerName);
            BlobClient blobClient = containerClient.GetBlobClient(name);

            await blobClient.UploadAsync(outputFileStream, new BlobHttpHeaders { ContentType = "application/octet-stream" });
        }
    }
}

备选方案（不推荐） #

如果一定要使用原inblobStream，则需要在调用加密方法前重置流的位置：

// 在EncryptStreamAsync前添加
inblobStream.Position = 0;
await pgp.EncryptStreamAsync(inblobStream, outputFileStream);

此方案依赖流支持重置操作，部分场景下可能不适用，因此优先推荐使用memoryStream的方案。

内容的提问来源于stack exchange，提问作者user26496939