Use PKCS8 PEM, not raw SEC1 bytes, to store VAPID keys.

The `web-push` crate's VAPID signing support requires a private key. The `p256` crate is more than capable of generating one, but the easiest way to get a key from a `p256::ecdsa::SigningKey` to a `web_push::PartialVapidSignature` is via PKCS #8 PEM, not via the bytes. Since we'll need it in that form anyways, store it that way, so that we don't have to decode it using `p256`, re-encode to PEM, then decode to `PartialVapidSignature`.

The migration in this commit invalidates existing VAPID keys. We could include support for re-encoding them on read, but there's little point: this code is still in flux anyways, and only development deployments exist. By the time this is final, the schema will have settled.

6 files changed, 35 insertions, 12 deletions

diff --git a/.sqlx/query-edd16f1507f3b40270d652c7c204a4b9a518af418cc7e7fce9a6f0a106a6d66e.json b/.sqlx/query-be295f56960d083d1f4c760f6acfdfbf9898a1a407e8a562a181542834d05eb0.json
index 2481fa9..ccec274 100644
--- a/.sqlx/query-edd16f1507f3b40270d652c7c204a4b9a518af418cc7e7fce9a6f0a106a6d66e.json
+++ b/.sqlx/query-be295f56960d083d1f4c760f6acfdfbf9898a1a407e8a562a181542834d05eb0.json
@@ -1,6 +1,6 @@
 {
   "db_name": "SQLite",
-  "query": "\n                select\n                    key.changed_at as \"changed_at: DateTime\",\n                    key.changed_sequence as \"changed_sequence: Sequence\",\n                    signing.key as \"key: Vec<u8>\"\n                from vapid_key as key\n                join vapid_signing_key as signing\n            ",
+  "query": "\n                select\n                    key.changed_at as \"changed_at: DateTime\",\n                    key.changed_sequence as \"changed_sequence: Sequence\",\n                    signing.key\n                from vapid_key as key\n                join vapid_signing_key as signing\n            ",
   "describe": {
     "columns": [
       {
@@ -14,9 +14,9 @@
         "type_info": "Integer"
       },
       {
-        "name": "key: Vec<u8>",
+        "name": "key",
         "ordinal": 2,
-        "type_info": "Blob"
+        "type_info": "Text"
       }
     ],
     "parameters": {
@@ -28,5 +28,5 @@
       false
     ]
   },
-  "hash": "edd16f1507f3b40270d652c7c204a4b9a518af418cc7e7fce9a6f0a106a6d66e"
+  "hash": "be295f56960d083d1f4c760f6acfdfbf9898a1a407e8a562a181542834d05eb0"
 }
diff --git a/migrations/20251028173914_pem_vapid_keys.sql b/migrations/20251028173914_pem_vapid_keys.sql
new file mode 100644
index 0000000..6302504
--- /dev/null
+++ b/migrations/20251028173914_pem_vapid_keys.sql
@@ -0,0 +1,15 @@
+drop table vapid_signing_key;
+
+create table vapid_signing_key (
+    key text
+        not null
+);
+
+create unique index vapid_signing_key_singleton
+    on vapid_signing_key (0);
+
+-- Whatever key we had, if any, was just destroyed by dropping the table. Delete the metadata
+-- as well so that the server will issue a new one.
+delete
+from
+    vapid_key;
diff --git a/src/boot/app.rs b/src/boot/app.rs
index 8da3e90..88255b0 100644
--- a/src/boot/app.rs
+++ b/src/boot/app.rs
@@ -78,6 +78,7 @@ pub enum Error {
     Database(#[from] sqlx::Error),
     Name(#[from] name::Error),
     Ecdsa(#[from] p256::ecdsa::Error),
+    Pkcs8(#[from] p256::pkcs8::Error),
 }
 
 impl From<user::repo::LoadError> for Error {
@@ -106,6 +107,7 @@ impl From<vapid::repo::Error> for Error {
         match error {
             Error::Database(error) => error.into(),
             Error::Ecdsa(error) => error.into(),
+            Error::Pkcs8(error) => error.into(),
         }
     }
 }
diff --git a/src/event/app.rs b/src/event/app.rs
index 6c657c7..1e471f1 100644
--- a/src/event/app.rs
+++ b/src/event/app.rs
@@ -98,6 +98,7 @@ pub enum Error {
     Database(#[from] sqlx::Error),
     Name(#[from] name::Error),
     Ecdsa(#[from] p256::ecdsa::Error),
+    Pkcs8(#[from] p256::pkcs8::Error),
 }
 
 impl From<user::repo::LoadError> for Error {
@@ -126,6 +127,7 @@ impl From<vapid::repo::Error> for Error {
         match error {
             Error::Database(error) => error.into(),
             Error::Ecdsa(error) => error.into(),
+            Error::Pkcs8(error) => error.into(),
         }
     }
 }
diff --git a/src/vapid/app.rs b/src/vapid/app.rs
index 5814ba0..b6e1bc5 100644
--- a/src/vapid/app.rs
+++ b/src/vapid/app.rs
@@ -86,11 +86,11 @@ impl<'a> Vapid<'a> {
 }
 
 #[derive(Debug, thiserror::Error)]
+#[error(transparent)]
 pub enum Error {
-    #[error(transparent)]
     Database(#[from] sqlx::Error),
-    #[error(transparent)]
     Ecdsa(#[from] p256::ecdsa::Error),
+    Pkcs8(#[from] p256::pkcs8::Error),
 }
 
 impl From<repo::Error> for Error {
@@ -99,6 +99,7 @@ impl From<repo::Error> for Error {
         match error {
             Error::Database(error) => error.into(),
             Error::Ecdsa(error) => error.into(),
+            Error::Pkcs8(error) => error.into(),
         }
     }
 }
diff --git a/src/vapid/repo.rs b/src/vapid/repo.rs
index 4ac5286..98b3bae 100644
--- a/src/vapid/repo.rs
+++ b/src/vapid/repo.rs
@@ -1,4 +1,7 @@
-use p256::{NistP256, ecdsa::SigningKey, elliptic_curve::FieldBytes};
+use p256::{
+    ecdsa::SigningKey,
+    pkcs8::{DecodePrivateKey as _, EncodePrivateKey as _, LineEnding},
+};
 use sqlx::{Sqlite, SqliteConnection, Transaction};
 
 use super::{
@@ -76,8 +79,8 @@ impl Vapid<'_> {
     }
 
     pub async fn store_signing_key(&mut self, key: &SigningKey) -> Result<(), Error> {
-        let key = key.to_bytes();
-        let key = key.as_slice();
+        let key = key.to_pkcs8_pem(LineEnding::CRLF)?;
+        let key = key.as_str();
         sqlx::query!(
             r#"
                 insert into vapid_signing_key (key)
@@ -97,14 +100,13 @@ impl Vapid<'_> {
                 select
                     key.changed_at as "changed_at: DateTime",
                     key.changed_sequence as "changed_sequence: Sequence",
-                    signing.key as "key: Vec<u8>"
+                    signing.key
                 from vapid_key as key
                 join vapid_signing_key as signing
             "#
         )
         .map(|row| {
-            let key = FieldBytes::<NistP256>::from_slice(&row.key);
-            let key = SigningKey::from_bytes(key)?;
+            let key = SigningKey::from_pkcs8_pem(&row.key)?;
             let key = key.verifying_key().to_owned();
 
             let changed = Instant::new(row.changed_at, row.changed_sequence);
@@ -122,6 +124,7 @@ impl Vapid<'_> {
 #[error(transparent)]
 pub enum Error {
     Ecdsa(#[from] p256::ecdsa::Error),
+    Pkcs8(#[from] p256::pkcs8::Error),
     Database(#[from] sqlx::Error),
 }