Struct PostPolicyV4Builder 

pub struct PostPolicyV4Builder { /* private fields */ }

Creates V4 Signed Policy Document (POST Object Forms).

This builder allows you to generate signed V4 POST policy documents for Google Cloud Storage. A Signed Policy Document enables unauthenticated users to upload files to GCS using an HTML form by providing a time-limited signature and enforcing conditions on the upload (like file size limits).

Example: Generating a Signed POST Policy

use std::time::Duration;
let policy = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "uploads/my-object.txt")
    .with_expiration(Duration::from_secs(3600)) // 1 hour
    .with_content_length_range(1, 10 * 1024 * 1024) // 1 byte to 10 MiB limit
    .with_starts_with("$key", "uploads/") // Enforce upload prefix
    .with_field("Content-Type", "text/plain") // Enforce content type
    .sign_with(signer)
    .await?;

println!("Upload URL: {}", policy.url);
for (key, value) in &policy.fields {
    println!("Form field -> {}: {}", key, value);
}

Example: Creating a Signer

You can use google-cloud-auth to create a Signer.

Using Application Default Credentials (ADC)

use google_cloud_auth::credentials::Builder;
use google_cloud_auth::signer::Signer;

let signer = Builder::default().build_signer()?;

Using a Service Account Key File

use google_cloud_auth::credentials::service_account::Builder;
use google_cloud_auth::signer::Signer;

let service_account_key = serde_json::json!({ /* add details here */ });
let signer = Builder::new(service_account_key).build_signer()?;

Implementations

impl PostPolicyV4Builder

pub fn for_object<B, O>(bucket: B, object: O) -> Self

where B: Into<String>, O: Into<String>,

Creates a new builder for the specified bucket and object.

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt");

pub fn with_expiration(self, expiration: Duration) -> Self

Sets the policy expiration duration. Maximum is 7 days (604,800 seconds).

Example

use std::time::Duration;

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_expiration(Duration::from_secs(3600));

pub fn with_url_style(self, url_style: UrlStyle) -> Self

Sets the URL formatting style.

Example

use google_cloud_storage::signed_url::UrlStyle;

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_url_style(UrlStyle::VirtualHostedStyle);

pub fn with_client_email<S: Into<String>>(self, client_email: S) -> Self

Sets the authorizer client email. If not set, it falls back to the signer’s email.

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_client_email("my-service-account@my-project.iam.gserviceaccount.com");

pub fn with_universe_domain<S: Into<String>>(self, universe_domain: S) -> Self

Sets the GCS universe domain (defaults to googleapis.com).

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_universe_domain("googleapis.com");

pub fn with_endpoint<S: Into<String>>(self, endpoint: S) -> Self

Sets a custom endpoint.

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_endpoint("https://private.googleapis.com");

pub fn with_field<K: Into<String>, V: Into<String>>( self, key: K, value: V, ) -> Self

Adds a form field/exact condition match (e.g. “acl” = “public-read”).

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_field("acl", "public-read")
    .with_field("Content-Type", "text/plain");

pub fn with_starts_with<F: Into<String>, P: Into<String>>( self, field: F, prefix: P, ) -> Self

Adds a starts-with condition constraint (e.g. “$key”, “uploads/”).

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_starts_with("$key", "uploads/");

pub fn with_content_length_range(self, min: u64, max: u64) -> Self

Adds a content-length-range constraint (minimum and maximum file size in bytes).

Example

let builder = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
    .with_content_length_range(1, 10 * 1024 * 1024); // 1 byte to 10 MiB

pub async fn sign_with( self, signer: &Signer, ) -> Result<PostPolicyV4Result, SigningError>

Sign the policy document.

Example

async fn run(signer: &Signer) -> anyhow::Result<()> {
    let policy = PostPolicyV4Builder::for_object("projects/_/buckets/my-bucket", "my-object.txt")
        .sign_with(signer)
        .await?;
}

Trait Implementations

impl Clone for PostPolicyV4Builder

fn clone(&self) -> PostPolicyV4Builder

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PostPolicyV4Builder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.