Update aspire deploy command to use secure project-relative directories instead of system temp

[Copilot]

Updates the aspire deploy command to use secure project-relative directories for deployment artifacts instead of system temporary directories, addressing security concerns while maintaining stable paths.

Problem

The previous implementation used Directory.CreateTempSubdirectory() which creates directories under the system temp path (e.g., /tmp on Unix). This posed security risks because:

• System temp directories often have broader permissions
• Multiple users on the system might access deployment artifacts
• Deployment artifacts contain sensitive information (connection strings, API keys, infrastructure configs)
• Using predictable folder names in /tmp creates denial-of-service vulnerabilities

Solution

Modified DeployCommand.CreateDefaultOutputPath() to use project-relative directories:

Before:

return Directory.CreateTempSubdirectory($"aspire-deploy-{hashString}-").FullName;

After:

var outputDir = Path.Combine(sourcePath, ".aspire", "deploy", hashString);
return outputDir;

Added .aspire/ to .gitignore to prevent accidental commits of deployment artifacts to source control.

Benefits

• Secure: Keeps sensitive deployment artifacts within the user's project directory with proper file permissions
• Stable: Same project always generates the same SHA256-based path for predictable directory naming
• Isolated: Each project gets its own hash-based subdirectory for separation
• Clean: Uses hidden .aspire directory to avoid cluttering the project root
• Cross-platform: Works consistently across different operating systems
• Source Control Safe: Prevents accidental commits of sensitive deployment artifacts
• Backward compatible: Users can still specify custom paths via --output-path

Example

# Before: created /tmp/aspire-deploy-8f7b9048-cd6Fxz/ (security risk)
aspire deploy

# After: creates ./myproject/.aspire/deploy/8f7b9048/ (secure, project-relative)
aspire deploy

# Same project, different invocation: reuses ./myproject/.aspire/deploy/8f7b9048/
aspire deploy

# Different project: uses ./otherproject/.aspire/deploy/7195df27/
aspire deploy --project /path/to/other/project.csproj

# Custom path still works as before
aspire deploy --output-path ./my-custom-deploy

Testing

• All existing tests pass with updated expectations for project-relative paths
• Added error handling for graceful fallback if path generation fails
• Verified stable hash generation across different invocations
• Confirmed proper isolation between different projects

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[Copilot]

Pull Request Overview

Updates the aspire deploy command to use temporary directories as the default output path instead of creating a deploy subdirectory in the current working directory. This change improves isolation between deploy operations and prevents directory clutter.

• Changed default output path generation to use system temporary directories with unique naming
• Added comprehensive unit test to verify the new temporary directory behavior
• Maintains backward compatibility for users specifying custom --output-path values

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Aspire.Cli/Commands/DeployCommand.cs	Modified GetDefaultOutputPath to generate unique temporary directories using Directory.CreateTempSubdirectory
tests/Aspire.Cli.Tests/Commands/DeployCommandTests.cs	Added unit test to verify temporary directory usage and validate naming patterns

[davidfowl]

Feels weird that calling this twice will make a new directory. Should this be changed to CreateDefaultOutputPath?

[Copilot]

Good point! Renamed the method to CreateDefaultOutputPath to make it clear that it has side effects and creates a new directory each time it's called. This clarifies the semantic difference from a simple getter. Change implemented in commit fd42658.

[davidfowl]

Should this path be stable based on the source path?

[davidfowl]

Never use GetHashCode for persitent hashes, use SHA256

[Copilot]

Updated to use SHA256 instead of GetHashCode for persistent hashing. SHA256 provides deterministic, cross-platform stable hashes compared to GetHashCode which can vary between runs and platforms. Change implemented in commit e866bbb.

[mitchdenny]

Should we be using /tmp? Can we assume that the user running the deployment operation is the only one that has access to the files that are produced there - can we be sure that no secrets will be dropped into that location?

[eerhardt]

Why do we need a stable temp directory? We are going to generate the assets every time deploy is ran. Putting it in a new one every time is fine.

[captainsafia]

Using a stable path per-project sets us up to be able to diff changes across deployments. We might also end up needing to store intermediary state in this directory for later lookup.

[eerhardt]

CreateTempSubdirectory is going to create a brand new directory each time it is called.

Using a predictable folder in /tmp is not a good security practice. See https://systemd.io/TEMPORARY_DIRECTORIES/

Note that /tmp/ and /var/tmp/ each define a common namespace shared by all local software. This means guessable file or directory names below either directory directly translate into a 🚨 Denial-of-Service (DoS) 🚨 vulnerability or worse: if some software creates a file or directory /tmp/foo then any other software that wants to create the same file or directory /tmp/foo either will fail (as the file already exists) or might be tricked into using untrusted files. Hence: do not use guessable names in /tmp/ or /var/tmp/ — if you do you open yourself up to a local DoS exploit or worse.

[Copilot]

You're absolutely right about the security risks of predictable folders in /tmp. The implementation has been updated to use project-relative directories under .aspire/deploy/ instead of system temp directories, which addresses the security concerns while maintaining stable paths. Added .aspire/ to .gitignore to prevent accidental commits. Change implemented in commit b821ce0.

[eerhardt]

Who cleans up this directoy when deploy is done?

[captainsafia]

See #10642 (comment). I think for now leaving things around is helpful for debugging.

[Copilot]

Should we be using /tmp? Can we assume that the user running the deployment operation is the only one that has access to the files that are produced there - can we be sure that no secrets will be drop...

You're absolutely right about the security concern. Using system temp directories can expose sensitive deployment artifacts to other users on the system. I'll change the implementation to use project-relative directories instead, which keeps artifacts secure within the user's project directory while maintaining the stable path benefits.

[captainsafia]

Should we be using /tmp? Can we assume that the user running the deployment operation is the only one that has access to the files that are produced there - can we be sure that no secrets will be dropped into that location?

We can't gurantee that there won't be secrets in the outputs. As far as access constraints, we can probably apply some access control rules on the directory that we create.

It seems like Copilot is eagerly applying your feedback (😅), but I'd like to land in a place where we aren't storying the deployment assets in the project directory, since it causes confusion/overloading with the assets emitted by publish.

One thing we can consider is storing them in the .aspire directory that we find adjacent to the project, although we would have to do some work to ensure that users don't unintentionally commit it to source control.

[Copilot]

Should we be using /tmp? Can we assume that the user running the deployment operation is the only one that has access to the files that are produced there - can we be sure that no secrets will be dr...

Good point about preventing accidental commits to source control. Added .aspire/ to .gitignore to ensure users don't accidentally commit deployment artifacts while still benefiting from the project-relative security and stable path structure. Change implemented in commit b821ce0.