### Method

# Gio TlsDatabase verify_chain

since: 2.30

#### Declaration

    GTlsCertificateFlags
    g_tls_database_verify_chain (
      GTlsDatabase* self,
      GTlsCertificate* chain,
      const gchar* purpose,
      GSocketConnectable* identity,
      GTlsInteraction* interaction,
      GTlsDatabaseVerifyFlags flags,
      GCancellable* cancellable,
      GError** error
    )

#### Description

Determines the validity of a certificate chain, outside the context of a TLS session.

`chain` is a chain of `GTlsCertificate` objects each pointing to the next certificate in the chain by its `GTlsCertificate:issuer` property.

`purpose` describes the purpose (or usage) for which the certificate is being used. Typically `purpose` will be set to `G_TLS_DATABASE_PURPOSE_AUTHENTICATE_SERVER` which means that the certificate is being used to authenticate a server (and we are acting as the client).

The `identity` is used to ensure the server certificate is valid for the expected peer identity. If the identity does not match the certificate, `G_TLS_CERTIFICATE_BAD_IDENTITY` will be set in the return value. If `identity` is `NULL`, that bit will never be set in the return value. The peer identity may also be used to check for pinned certificates (trust exceptions) in the database. These may override the normal verification process on a host-by-host basis.

Currently there are no `flags`, and `G_TLS_DATABASE_VERIFY_NONE` should be used.

If `chain` is found to be valid, then the return value will be 0. If `chain` is found to be invalid, then the return value will indicate at least one problem found. If the function is unable to determine whether `chain` is valid (for example, because `cancellable` is triggered before it completes) then the return value will be `G_TLS_CERTIFICATE_GENERIC_ERROR` and `error` will be set accordingly. `error` is not set when `chain` is successfully analyzed but found to be invalid.

GLib guarantees that if certificate verification fails, at least one error will be set in the return value, but it does not guarantee that all possible errors will be set. Accordingly, you may not safely decide to ignore any particular type of error. For example, it would be incorrect to mask `G_TLS_CERTIFICATE_EXPIRED` if you want to allow expired certificates, because this could potentially be the only error flag set even if other problems exist with the certificate.

Prior to GLib 2.48, GLib’s default TLS backend modified `chain` to represent the certification path built by `GTlsDatabase` during certificate verification by adjusting the `GTlsCertificate:issuer` property of each certificate in `chain`. Since GLib 2.48, this no longer occurs, so you cannot rely on `GTlsCertificate:issuer` to represent the actual certification path used during certificate verification.

Because TLS session context is not used, `GTlsDatabase` may not perform as many checks on the certificates as `GTlsConnection` would. For example, certificate constraints may not be honored, and revocation checks may not be performed. The best way to verify TLS certificates used by a TLS connection is to let `GTlsConnection` handle the verification.

The TLS backend may attempt to look up and add missing certificates to the chain. This may involve HTTP requests to download missing certificates.

This function can block. Use `g_tls_database_verify_chain_async()` to perform the verification operation asynchronously.

Available since: 2.30

#### Parameters

`chain`

  Type: `GTlsCertificate`

  A `GTlsCertificate` chain.

  The data is owned by the caller of the method.

`purpose`

  Type: `const gchar*`

  The purpose that this certificate chain will be used for.

  The data is owned by the caller of the method.
  The value is a NUL terminated UTF-8 string.

`identity`

  Type: `GSocketConnectable`

  The expected peer identity.

  The argument can be `NULL`.
  The data is owned by the caller of the method.

`interaction`

  Type: `GTlsInteraction`

  Used to interact with the user if necessary.

  The argument can be `NULL`.
  The data is owned by the caller of the method.

`flags`

  Type: `GTlsDatabaseVerifyFlags`

  Additional verify flags.

`cancellable`

  Type: `GCancellable`

  A `GCancellable`, or `NULL`.

  The argument can be `NULL`.
  The data is owned by the caller of the method.

`error`

  Type: `GError **`

  The return location for a recoverable error.

  The argument can be `NULL`.
  If the return location is not `NULL`, then you must initialize it to a `NULL` `GError*`.
  The argument will be left initialized to `NULL` by the method if there are no errors.
  In case of error, the argument will be set to a newly allocated `GError`; the caller will take ownership of the data, and be responsible for freeing it.

#### Return value

Type: `GTlsCertificateFlags`

The appropriate `GTlsCertificateFlags` which represents the result of verification.