Source

File: wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

public function check_read_permission( $post ) {
		$post_type = get_post_type_object( $post->post_type );
		if ( ! $this->check_is_post_type_allowed( $post_type ) ) {
			return false;
		}

		// Is the post readable?
		if ( 'publish' === $post->post_status || current_user_can( 'read_post', $post->ID ) ) {
			return true;
		}

		$post_status_obj = get_post_status_object( $post->post_status );
		if ( $post_status_obj && $post_status_obj->public ) {
			return true;
		}

		// Can we read the parent if we're inheriting?
		if ( 'inherit' === $post->post_status && $post->post_parent > 0 ) {
			$parent = get_post( $post->post_parent );
			if ( $parent ) {
				return $this->check_read_permission( $parent );
			}
		}

		/*
		 * If there isn't a parent, but the status is set to inherit, assume
		 * it's published (as per get_post_status()).
		 */
		if ( 'inherit' === $post->post_status ) {
			return true;
		}

		return false;
	}