feat(sharing): expose a public link's custom password

get_public_link recovers the custom password along with the URL fragment,
so a caller can keep it while update_public_link changes the role or the
expiry. Debug for PublicLink and Bookmark redacts the URL and the custom
password.

CHANGELOG.md

@@ -25,6 +25,9 @@ This file starts after 0.9.2; earlier changes are in the git history.
   expiry of the link on a node. The URL does not change. `None` removes a custom
   password or an expiry. A legacy link cannot be updated. Ported from the
   TypeScript SDK (`updateSharedLink`).
+- **A public link's custom password.** `PublicLink::custom_password` holds the
+  custom password of a link, recovered from the stored link password, so a
+  caller can keep it while `update_public_link` changes the role or the expiry.
 - **Walking a public link.** `ProtonDrivePublicLinkClient::enumerate_subtree`
   and `enumerate_subtree_reporting` return every node below a shared folder,
   breadth first, listing several folders of a level at once.
@@ -50,6 +53,8 @@ This file starts after 0.9.2; earlier changes are in the git history.
   is retried under the client's retry policy. A write still is not: it may have
   been applied. Read-only POSTs in `proton-drive-rs` (link details, thumbnails,
   photo duplicates, `checkAvailableHashes`) now use `post_query`.
+- `Debug` for `PublicLink` and `Bookmark` no longer prints the URL or the
+  custom password; it shows `<redacted>` instead.
 - `remove_photos_from_album` refuses a photo on another volume per photo, in
   the input order, without sending it.
 
@@ -60,6 +65,6 @@ This file starts after 0.9.2; earlier changes are in the git history.
 
 ### Breaking
 
-- `Bookmark` has a new public field, `custom_password`. Code that builds a
+- `Bookmark` and `PublicLink` have a new public field, `custom_password`. Code
-  `Bookmark` with a struct literal must set it.
+  that builds either with a struct literal must set it.
 - `ResponseCode` has a new variant. An exhaustive `match` on it needs an arm.

crates/proton-drive-rs/src/client.rs

@@ -3794,6 +3794,7 @@ impl ProtonDriveClient {
             creation_time: now_epoch_seconds(),
             expiration_time,
             has_custom_password,
+            custom_password: custom_password.filter(|p| !p.is_empty()).map(str::to_owned),
         })
     }
 
@@ -3856,6 +3857,7 @@ impl ProtonDriveClient {
             role,
             expiration_time,
             has_custom_password,
+            custom_password: custom_password.filter(|p| !p.is_empty()).map(str::to_owned),
             ..link
         })
     }
@@ -3936,7 +3938,7 @@ impl ProtonDriveClient {
                 let response: ShareUrlsResponse = self.http.get(&path).await?;
                 match response.share_urls.into_iter().next() {
                     Some(dto) => {
-                        let url = self.recover_public_link_url(&dto).await;
+                        let (url, custom_password) = self.recover_public_link_secret(&dto).await;
                         Some(PublicLink {
                             share_id,
                             public_link_id: dto.share_url_id,
@@ -3945,6 +3947,7 @@ impl ProtonDriveClient {
                             creation_time: dto.create_time,
                             expiration_time: dto.expiration_time,
                             has_custom_password: dto.flags == 3,
+                            custom_password,
                         })
                     }
                     None => None,
@@ -3956,24 +3959,32 @@ impl ProtonDriveClient {
         Ok(link)
     }
 
-    /// Rebuild the full public URL (`{public_url}#{generated}`) for an existing
+    /// Rebuild the full public URL (`{public_url}#{generated}`) and the custom
-    /// link by decrypting its stored `Password` with the owner's address key. The
+    /// password of an existing link by decrypting its stored `Password` with the
-    /// stored secret is the generated password with any custom password appended;
+    /// owner's address key. The stored secret is the generated password with any
-    /// only the leading generated portion belongs in the URL fragment (the
+    /// custom password appended; only the leading generated portion belongs in
-    /// recipient supplies the custom password separately). Returns `None` if the
+    /// the URL fragment (the recipient supplies the custom password separately).
-    /// link carries no password or it can't be decrypted, so the caller still gets
+    /// Both are `None` if the link carries no password or it can't be
-    /// the link's metadata.
+    /// decrypted, so the caller still gets the link's metadata.
-    async fn recover_public_link_url(&self, dto: &ShareUrlDto) -> Option<String> {
+    async fn recover_public_link_secret(
-        if dto.public_url.is_empty() {
+        &self,
-            return None;
+        dto: &ShareUrlDto,
-        }
+    ) -> (Option<String>, Option<String>) {
-        let enc = dto.password.as_deref()?;
+        let Some(enc) = dto.password.as_deref() else {
+            return (None, None);
+        };
+        let full = async {
             let (_, email, _) = self.membership_address().await.ok()?;
             let (address_keys, _) = self.own_address_keys(&email).await.ok()?;
             let bytes = decrypt_armored_with_keys(enc, &address_keys).ok()?;
-        let full = String::from_utf8_lossy(&bytes);
+            Some(String::from_utf8_lossy(&bytes).into_owned())
-        let generated: String = full.chars().take(PUBLIC_LINK_PASSWORD_LEN).collect();
+        };
-        Some(format!("{}#{generated}", dto.public_url))
+        let Some(full) = full.await else {
+            return (None, None);
+        };
+        let (generated, custom) = split_link_password(&full);
+        let url = (!dto.public_url.is_empty()).then(|| format!("{}#{generated}", dto.public_url));
+        (url, custom.map(str::to_owned))
     }
 
     /// Remove a public link, revoking access via the URL
@@ -4221,7 +4232,7 @@ impl ProtonDriveClient {
             // fragment is the generated part; the share key is locked with the
             // whole string.
             let password = String::from_utf8_lossy(&bytes).into_owned();
-            let (url_password, custom_password) = split_bookmark_password(&password);
+            let (url_password, custom_password) = split_link_password(&password);
             let url = format!(
                 "https://drive.proton.me/urls/{}#{url_password}",
                 dto.token.token
@@ -8078,9 +8089,9 @@ fn public_link_permissions(role: MemberRole) -> Result<i32> {
         })
 }
 
-/// Split a bookmark's stored secret into the generated URL password and the
+/// Split a public link's stored secret into the generated URL password and the
 /// custom password appended to it, if any (TS `splitGeneratedAndCustomPassword`).
-fn split_bookmark_password(password: &str) -> (&str, Option<&str>) {
+fn split_link_password(password: &str) -> (&str, Option<&str>) {
     let split = password
         .char_indices()
         .nth(PUBLIC_LINK_PASSWORD_LEN)
@@ -8984,7 +8995,7 @@ mod tests {
         is_listable_revision_state, is_upload_timeout, join_node_path, missing_related_links,
         path_segments, photos_only_in_album, record_transfer_outcome, resolve_parent_keys,
         run_context_share_mutation, share_membership_from_dto, small_upload_applicable,
-        small_upload_should_fall_back, split_bookmark_password, take_block_target,
+        small_upload_should_fall_back, split_link_password, take_block_target,
         take_thumbnail_target, to_drive_event, validate_node_name,
     };
     use crate::dtos::{
@@ -9003,23 +9014,20 @@ mod tests {
     use tokio::sync::{Mutex, Notify, RwLock};
 
     #[test]
-    fn a_bookmark_password_splits_into_the_generated_part_and_the_custom_one() {
+    fn a_link_password_splits_into_the_generated_part_and_the_custom_one() {
+        assert_eq!(split_link_password("AbCdEf123456"), ("AbCdEf123456", None));
         assert_eq!(
-            split_bookmark_password("AbCdEf123456"),
+            split_link_password("AbCdEf123456s3cr3t!"),
-            ("AbCdEf123456", None)
-        );
-        assert_eq!(
-            split_bookmark_password("AbCdEf123456s3cr3t!"),
             ("AbCdEf123456", Some("s3cr3t!"))
         );
         // A custom password may hold any character; the split counts chars,
         // not bytes, and never cuts one in half.
         assert_eq!(
-            split_bookmark_password("AbCdEf123456pässwört"),
+            split_link_password("AbCdEf123456pässwört"),
             ("AbCdEf123456", Some("pässwört"))
         );
         // A legacy password shorter than a generated one is all URL password.
-        assert_eq!(split_bookmark_password("short"), ("short", None));
+        assert_eq!(split_link_password("short"), ("short", None));
     }
 
     /// A batch envelope with one successful link and one that failed with `code`.

crates/proton-drive-rs/src/sharing.rs

@@ -5,6 +5,8 @@
 //! expose; the behavior is ported from the TypeScript SDK (`internal/sharing`).
 //! Reading shared-with-me nodes and leaving them lives on the client already.
 
+use std::fmt;
+
 use proton_sdk::crypto::VerificationStatus;
 use proton_sdk::ids::{NodeUid, ShareId, ShareMembershipId};
 use serde::{Deserialize, Serialize};
@@ -149,7 +151,9 @@ pub struct ShareMember {
 }
 
 /// A public share link on a node.
-#[derive(Debug, Clone)]
+///
+/// `Debug` leaves out the custom password.
+#[derive(Clone)]
 pub struct PublicLink {
     /// The share this link belongs to.
     pub share_id: ShareId,
@@ -166,6 +170,31 @@ pub struct PublicLink {
     pub expiration_time: Option<i64>,
     /// Whether the link is additionally protected by a custom password.
     pub has_custom_password: bool,
+    /// The custom password itself, when the link has one and the stored link
+    /// password could be decrypted. Pass it back to
+    /// [`update_public_link`](crate::ProtonDriveClient::update_public_link) to
+    /// keep it while changing the role or the expiry.
+    pub custom_password: Option<String>,
+}
+
+impl fmt::Debug for PublicLink {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("PublicLink")
+            .field("share_id", &self.share_id)
+            .field("public_link_id", &self.public_link_id)
+            .field("url", &redacted(&self.url))
+            .field("role", &self.role)
+            .field("creation_time", &self.creation_time)
+            .field("expiration_time", &self.expiration_time)
+            .field("has_custom_password", &self.has_custom_password)
+            .field("custom_password", &redacted(&self.custom_password))
+            .finish()
+    }
+}
+
+/// What `Debug` shows for a secret: whether there is one, never its value.
+fn redacted(secret: &Option<String>) -> Option<&'static str> {
+    secret.as_ref().map(|_| "<redacted>")
 }
 
 /// A pending invitation to a Proton user (not yet accepted).
@@ -250,7 +279,9 @@ pub struct IncomingInvitation {
 
 /// A public link the user has saved to their account ("bookmark"). Opening it
 /// visits the public URL; there is no local copy.
-#[derive(Debug, Clone)]
+///
+/// `Debug` leaves out the URL's secret fragment and the custom password.
+#[derive(Clone)]
 pub struct Bookmark {
     /// The bookmark's token — the handle for
     /// [`delete_bookmark`](crate::ProtonDriveClient::delete_bookmark).
@@ -270,10 +301,51 @@ pub struct Bookmark {
     pub creation_time: i64,
 }
 
+impl fmt::Debug for Bookmark {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Bookmark")
+            .field("token", &self.token)
+            .field("url", &"<redacted>")
+            .field("custom_password", &redacted(&self.custom_password))
+            .field("node_name", &self.node_name)
+            .field("is_folder", &self.is_folder)
+            .field("creation_time", &self.creation_time)
+            .finish()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn debug_output_leaves_out_link_secrets() {
+        let link = PublicLink {
+            share_id: "s1".into(),
+            public_link_id: "l1".into(),
+            url: Some("https://drive.proton.me/urls/T0K3N#AbCdEf123456".into()),
+            role: MemberRole::Viewer,
+            creation_time: 1,
+            expiration_time: None,
+            has_custom_password: true,
+            custom_password: Some("s3cr3t".into()),
+        };
+        let bookmark = Bookmark {
+            token: "T0K3N".into(),
+            url: "https://drive.proton.me/urls/T0K3N#AbCdEf123456".into(),
+            custom_password: Some("s3cr3t".into()),
+            node_name: Some("Holiday".into()),
+            is_folder: true,
+            creation_time: 1,
+        };
+        for shown in [format!("{link:?}"), format!("{bookmark:?}")] {
+            assert!(!shown.contains("AbCdEf123456"), "{shown}");
+            assert!(!shown.contains("s3cr3t"), "{shown}");
+            assert!(shown.contains("<redacted>"), "{shown}");
+        }
+        assert!(format!("{bookmark:?}").contains("Holiday"));
+    }
+
     #[test]
     fn the_strict_role_mapping_refuses_to_guess_at_an_unknown_mask() {
         // The three masks Proton actually uses, plus the absent case.

crates/proton-drive-rs/tests/live_sharing.rs

@@ -846,6 +846,11 @@ async fn update_public_link_changes_role_password_and_expiry() {
         "the expiry must be stored"
     );
     assert_eq!(fetched.url.as_deref(), Some(url.as_str()));
+    assert_eq!(
+        fetched.custom_password.as_deref(),
+        Some(custom),
+        "the custom password is recovered from the stored link password"
+    );
 
     assert!(
         ProtonDrivePublicLinkClient::open(common::config(), &url, None)
@@ -873,6 +878,7 @@ async fn update_public_link_changes_role_password_and_expiry() {
         "the custom password is removed"
     );
     assert_eq!(fetched.expiration_time, None, "the expiry is cleared");
+    assert_eq!(fetched.custom_password, None);
     ProtonDrivePublicLinkClient::open(common::config(), &url, None)
         .await
         .expect("the link opens with the URL alone again");