Add helper for paring down signers to those requried by a tx message (bp #15899) (#15937)

* sdk: Add accessor for signer pubkeys of a tx message

(cherry picked from commit bf33ce8906)

* clap-utils: Add helper to `CliSignerInfo` for getting signers for a message

(cherry picked from commit 4e99f1e634)

Co-authored-by: Trent Nelson <trent@solana.com>

clap-utils/src/keypair.rs

@@ -12,6 +12,7 @@ use solana_remote_wallet::{
 };
 use solana_sdk::{
     hash::Hash,
+    message::Message,
     pubkey::Pubkey,
     signature::{
         keypair_from_seed, keypair_from_seed_phrase_and_passphrase, read_keypair,
@@ -68,6 +69,18 @@ impl CliSignerInfo {
             None
         }
     }
+    pub fn signers_for_message(&self, message: &Message) -> Vec<&dyn Signer> {
+        self.signers
+            .iter()
+            .filter_map(|k| {
+                if message.signer_keys().contains(&&k.pubkey()) {
+                    Some(k.as_ref())
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
 }
 
 pub struct DefaultSigner {
@@ -356,6 +369,7 @@ fn sanitize_seed_phrase(seed_phrase: &str) -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use solana_sdk::system_instruction;
 
     #[test]
     fn test_sanitize_seed_phrase() {
@@ -365,4 +379,35 @@ mod tests {
             sanitize_seed_phrase(seed_phrase)
         );
     }
+
+    #[test]
+    fn test_signer_info_signers_for_message() {
+        let source = Keypair::new();
+        let fee_payer = Keypair::new();
+        let nonsigner1 = Keypair::new();
+        let nonsigner2 = Keypair::new();
+        let recipient = Pubkey::new_unique();
+        let message = Message::new(
+            &[system_instruction::transfer(
+                &source.pubkey(),
+                &recipient,
+                42,
+            )],
+            Some(&fee_payer.pubkey()),
+        );
+        let signers = vec![
+            Box::new(fee_payer) as Box<dyn Signer>,
+            Box::new(source) as Box<dyn Signer>,
+            Box::new(nonsigner1) as Box<dyn Signer>,
+            Box::new(nonsigner2) as Box<dyn Signer>,
+        ];
+        let signer_info = CliSignerInfo { signers };
+        let msg_signers = signer_info.signers_for_message(&message);
+        let signer_pubkeys = msg_signers.iter().map(|s| s.pubkey()).collect::<Vec<_>>();
+        let expect = vec![
+            signer_info.signers[0].pubkey(),
+            signer_info.signers[1].pubkey(),
+        ];
+        assert_eq!(signer_pubkeys, expect);
+    }
 }

sdk/program/src/message.rs

@@ -435,6 +435,15 @@ impl Message {
             accounts,
         })
     }
+
+    pub fn signer_keys(&self) -> Vec<&Pubkey> {
+        // Clamp in case we're working on un-`sanitize()`ed input
+        let last_key = self
+            .account_keys
+            .len()
+            .max(self.header.num_required_signatures as usize);
+        self.account_keys[..last_key].iter().collect()
+    }
 }
 
 #[cfg(test)]