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Enforce and document file hash requirement for MCPB packages (#368)

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## Summary
Implements mandatory file hash validation for MCPB (MCP Bundle) packages
to ensure file integrity and security.

## Changes
- **Validator enforcement**: MCPB packages now require `file_sha256`
field at publish time
- **Test coverage**: Updated all MCPB test cases to include valid
SHA-256 hashes
- **Documentation**: Updated publisher guide and schema to reflect hash
requirement
- **Error handling**: Clear error message when hash is missing

## Security Impact
This ensures the complete security workflow for MCPB packages:
1. Authors generate and provide SHA-256 hashes when publishing
2. Registry validates hash is present (but doesn't verify content)
3. MCP clients validate hash matches downloaded file before installation

Fixes #351
This commit is contained in:
adam jones 2025-09-08 11:38:25 -07:00 • committed by GitHub
commit 8f5e17d0fe
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2 changed files with 72 additions and 24 deletions
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18
docs/guides/publishing/publish-server.md
View file

@ -219,6 +219,15 @@ The official MCP registry currently only supports the official Docker registry (
### Requirements
**MCP reference** - MCPB package URLs must contain "mcp" somewhere within them, to ensure the correct artifact has been uploaded. This may be with the `.mcpb` extension or in the name of your repository.
**File integrity** - MCPB packages must include a SHA-256 hash for file integrity verification. This is required at publish time and MCP clients will validate this hash before installation.
### How to Generate File Hashes
Calculate the SHA-256 hash of your MCPB file:
```bash
openssl dgst -sha256 server.mcpb
```
### Example server.json
```json
{
@ -226,12 +235,19 @@ The official MCP registry currently only supports the official Docker registry (
"packages": [
{
"registry_type": "mcpb",
"identifier": "https://github.com/you/your-repo/releases/download/v1.0.0/server.mcpb"
"identifier": "https://github.com/you/your-repo/releases/download/v1.0.0/server.mcpb",
"file_sha256": "fe333e598595000ae021bd27117db32ec69af6987f507ba7a63c90638ff633ce"
}
]
}
```
### File Hash Validation
- **Authors** are responsible for generating correct SHA-256 hashes when creating server.json
- **MCP clients** validate the hash before installing packages to ensure file integrity
- **The official registry** stores hashes but does not validate them
- **Subregistries** may choose to implement their own validation. This enables them to perform security scanning on MCPB files, and ensure clients get the same security scanned content.
The official MCP registry currently only supports artifacts hosted on GitHub or GitLab releases.
</details>

3
docs/reference/server-json/server.schema.json
View file

@ -115,7 +115,8 @@
},
"file_sha256": {
"type": "string",
"description": "SHA-256 hash of the package file for integrity verification.",
"pattern": "^[a-f0-9]{64}$",
"description": "SHA-256 hash of the package file for integrity verification. Required for MCPB packages and optional for other package types. Authors are responsible for generating correct SHA-256 hashes when creating server.json. If present, MCP clients must validate the downloaded file matches the hash before running packages to ensure file integrity.",
"example": "fe333e598595000ae021bd27117db32ec69af6987f507ba7a63c90638ff633ce"
},
"runtime_hint": {