Repository signatures

Artikel
01/25/2021

If a package source supports adding repository signatures to published packages, it is possible for a client to determine the signing certificates that are used by the package source. This resource allows clients to detect whether a repository signed package has been tampered or has an unexpected signing certificate.

The resource used for fetching this repository signature information is the RepositorySignatures resource found in the service index.

Versioning

The following @type value is used:

@type value	Notes
RepositorySignatures/4.7.0	The initial release
RepositorySignatures/4.9.0	Supported by NuGet v4.9+ clients
RepositorySignatures/5.0.0	Allows enabling `allRepositorySigned`. Supported by NuGet v5.0+ clients

Base URL

The entry point URL for the following APIs is the value of the @id property associated with the aforementioned resource @type value. This topic uses the placeholder URL {@id}.

Note that unlike other resources, the {@id} URL is required to be served over HTTPS.

HTTP methods

All URLs found in the repository signatures resource support only the HTTP methods GET and HEAD.

Repository signatures index

The repository signatures index contains two pieces of information:

Whether or not all packages found on the source are repository signed by this package source.
The list of certificates used by the package source to sign packages.

In most cases, the list of certificates will only ever be appended to. New certificates would be added to the list when the previous signing certificate has expired and the package source needs to start using a new signing certificate. If a certificate is removed from the list, that means that all package signatures created with the removed signing certificate should no longer be considered valid by the client. In this case, the package signature (but not necessarily the package) is invalid. A client policy may allow installing the package as unsigned.

In the case of certificate revocation (e.g. key compromise), the package source is expected to re-sign all packages signed by the affected certificate. Additionally, the package source should remove the affected certificate from the signing certificate list.

The following request fetches the repository signatures index.

GET {@id}

The repository signature index is a JSON document that contains an object with the following properties:

Name	Type	Required	Notes
allRepositorySigned	boolean	yes	Must be `false` on 4.7.0 and 4.9.0 resources
signingCertificates	array of objects	yes

The allRepositorySigned boolean is set to false if the package source has some packages that have no repository signature. If the boolean is set to true, all packages available on the source must have a repository signature produced by one of the signing certificates mentioned in signingCertificates.

Warning

The allRepositorySigned boolean must be false on the 4.7.0 and 4.9.0 resources. NuGet v4.7, v4.8, and v4.9 clients cannot install packages from sources that have allRepositorySigned set to true.

There should be one or more signing certificates in the signingCertificates array if the allRepositorySigned boolean is set to true. If the array is empty and allRepositorySigned is set to true, all packages from the source should be considered invalid, although a client policy may still allow consumption of packages. Each element in this array is a JSON object with the following properties.

Name	Type	Required	Notes
contentUrl	string	yes	Absolute URL to the DER-encoded public certificate
fingerprints	object	yes
subject	string	yes	The subject distinguished name from the certificate
issuer	string	yes	The distinguished name of the certificate's issuer
notBefore	string	yes	The starting timestamp of the certificate's validity period
notAfter	string	yes	The ending timestamp of the certificate's validity period

Note that the contentUrl is required to be served over HTTPS. This URL has no specific URL pattern and must be dynamically discovered using this repository signatures index document.

All properties in this object (aside from contentUrl) must be derivable from the certificate found at contentUrl. These derivable properties are provided as a convenience to minimize round trips.

The fingerprints object has the following properties:

Name	Type	Required	Notes
2.16.840.1.101.3.4.2.1	string	yes	The SHA-256 fingerprint

The key name 2.16.840.1.101.3.4.2.1 is the OID of the SHA-256 hash algorithm.

All hash values must be lowercase, hex-encoded string representations of the hash digest.

Sample request

GET https://api.nuget.org/v3-index/repository-signatures/5.0.0/index.json

Sample response

{
  "allRepositorySigned": true,
  "signingCertificates": [
    {
      "fingerprints": {
        "2.16.840.1.101.3.4.2.1": "0e5f38f57dc1bcc806d8494f4f90fbcedd988b46760709cbeec6f4219aa6157d"
      },
      "subject": "CN=NuGet.org Repository by Microsoft, O=NuGet.org Repository by Microsoft, L=Redmond, S=Washington, C=US",
      "issuer": "CN=DigiCert SHA2 Assured ID Code Signing CA, OU=www.digicert.com, O=DigiCert Inc, C=US",
      "notBefore": "2018-04-10T00:00:00.0000000Z",
      "notAfter": "2021-04-14T12:00:00.0000000Z",
      "contentUrl": "https://api.nuget.org/v3-index/repository-signatures/certificates/0e5f38f57dc1bcc806d8494f4f90fbcedd988b46760709cbeec6f4219aa6157d.crt"
    },
    {
      "fingerprints": {
        "2.16.840.1.101.3.4.2.1": "5a2901d6ada3d18260b9c6dfe2133c95d74b9eef6ae0e5dc334c8454d1477df4"
      },
      "subject": "CN=NuGet.org Repository by Microsoft, O=NuGet.org Repository by Microsoft, L=Redmond, S=Washington, C=US",
      "issuer": "CN=DigiCert SHA2 Assured ID Code Signing CA, OU=www.digicert.com, O=DigiCert Inc, C=US",
      "notBefore": "2021-02-16T00:00:00.0000000Z",
      "notAfter": "2024-05-15T23:59:59.0000000Z",
      "contentUrl": "https://api.nuget.org/v3-index/repository-signatures/certificates/5a2901d6ada3d18260b9c6dfe2133c95d74b9eef6ae0e5dc334c8454d1477df4.crt"
    },
    {
      "fingerprints": {
        "2.16.840.1.101.3.4.2.1": "1f4b311d9acc115c8dc8018b5a49e00fce6da8e2855f9f014ca6f34570bc482d"
      },
      "subject": "CN=NuGet.org Repository by Microsoft, O=NuGet.org Repository by Microsoft, L=Redmond, S=Washington, C=US",
      "issuer": "CN=DigiCert Trusted G4 Code Signing RSA4096 SHA384 2021 CA1, O=\"DigiCert, Inc.\", C=US",
      "notBefore": "2024-02-23T00:00:00.0000000Z",
      "notAfter": "2027-05-18T23:59:59.0000000Z",
      "contentUrl": "https://api.nuget.org/v3-index/repository-signatures/certificates/1f4b311d9acc115c8dc8018b5a49e00fce6da8e2855f9f014ca6f34570bc482d.crt"
    }
  ]
}

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