From c856b82c2e29bc900a6d4135b8bb5cc759630bac Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Sun, 24 Mar 2024 15:57:49 +0100
Subject: [PATCH] libstore: despecialcase protocol version check

protocol versions are sent as u64. on the peer we read them as uint64,
check that the upper half is 0, and throw an exception if not. we then
read an arbitrary amount of data from the peer and dump it to the user
terminal. this is a little bit ridiculous, can never happen in correct
implementation, and is severly untested. let us just drop it entirely.

Change-Id: Ibd2f53a765341ed6439d40d9d1eac11e79c6b5e3
---
 src/libstore/legacy-ssh-store.cc | 17 +++--------------
 src/libstore/remote-store.cc     | 17 ++++-------------
 2 files changed, 7 insertions(+), 27 deletions(-)

diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index 890c8a149..2d8667a85 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -124,20 +124,9 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
             conn->to << SERVE_MAGIC_1 << SERVE_PROTOCOL_VERSION;
             conn->to.flush();
 
-            StringSink saved;
-            try {
-                TeeSource tee(conn->from, saved);
-                unsigned int magic = readInt(tee);
-                if (magic != SERVE_MAGIC_2)
-                    throw Error("'nix-store --serve' protocol mismatch from '%s'", host);
-            } catch (SerialisationError & e) {
-                /* In case the other side is waiting for our input,
-                   close it. */
-                conn->sshConn->in.close();
-                auto msg = conn->from.drain();
-                throw Error("'nix-store --serve' protocol mismatch from '%s', got '%s'",
-                    host, chomp(saved.s + msg));
-            }
+            uint64_t magic = readLongLong(conn->from);
+            if (magic != SERVE_MAGIC_2)
+                throw Error("'nix-store --serve' protocol mismatch from '%s'", host);
             conn->remoteVersion = readInt(conn->from);
             if (GET_PROTOCOL_MAJOR(conn->remoteVersion) != 0x200)
                 throw Error("unsupported 'nix-store --serve' protocol version on '%s'", host);
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 7572473cf..f0dbe8e21 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -69,19 +69,10 @@ void RemoteStore::initConnection(Connection & conn)
         conn.from.endOfFileError = "Nix daemon disconnected unexpectedly (maybe it crashed?)";
         conn.to << WORKER_MAGIC_1;
         conn.to.flush();
-        StringSink saved;
-        try {
-            TeeSource tee(conn.from, saved);
-            unsigned int magic = readInt(tee);
-            if (magic != WORKER_MAGIC_2)
-                throw Error("protocol mismatch");
-        } catch (SerialisationError & e) {
-            /* In case the other side is waiting for our input, close
-               it. */
-            conn.closeWrite();
-            auto msg = conn.from.drain();
-            throw Error("protocol mismatch, got '%s'", chomp(saved.s + msg));
-        }
+
+        uint64_t magic = readLongLong(conn.from);
+        if (magic != WORKER_MAGIC_2)
+            throw Error("protocol mismatch");
 
         conn.from >> conn.daemonVersion;
         if (GET_PROTOCOL_MAJOR(conn.daemonVersion) != GET_PROTOCOL_MAJOR(PROTOCOL_VERSION))