From b74c0c1ebcb6062cac53a8716cfabf7d94420dc4 Mon Sep 17 00:00:00 2001
From: Tad Glines <taglines@microsoft.com>
Date: Wed, 17 Nov 2021 13:24:57 -0800
Subject: [PATCH] Add support for abstract UDS addresses (#90)

---
 OutputInputTests.cpp   |  6 +++---
 UnixDomainListener.cpp | 26 ++++++++++++++++++++------
 UnixDomainWriter.cpp   | 10 ++++++++++
 3 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/OutputInputTests.cpp b/OutputInputTests.cpp
index 45e3542..e46b04e 100644
--- a/OutputInputTests.cpp
+++ b/OutputInputTests.cpp
@@ -61,7 +61,7 @@ int GetEventSeq(const Event& event) {
 BOOST_AUTO_TEST_CASE( basic_test ) {
     TempDir dir("/tmp/OutputInputTests");
 
-    std::string socket_path = dir.Path() + "/input.socket";
+    std::string socket_path = "@input.socket@@@@";
     std::string status_socket_path = dir.Path() + "/status.socket";
 
     std::mutex log_mutex;
@@ -160,7 +160,7 @@ BOOST_AUTO_TEST_CASE( basic_test ) {
 BOOST_AUTO_TEST_CASE( same_event_id_test ) {
     TempDir dir("/tmp/OutputInputTests");
 
-    std::string socket_path = dir.Path() + "/input.socket";
+    std::string socket_path = "@input.socket@@@@@@";
     std::string status_socket_path = dir.Path() + "/status.socket";
 
     std::mutex log_mutex;
@@ -260,7 +260,7 @@ BOOST_AUTO_TEST_CASE( same_event_id_test ) {
 BOOST_AUTO_TEST_CASE( dropped_acks_test ) {
     TempDir dir("/tmp/OutputInputTests");
 
-    std::string socket_path = dir.Path() + "/input.socket";
+    std::string socket_path = "@input.socket@@@@@@";
     std::string status_socket_path = dir.Path() + "/status.socket";
 
     std::mutex log_mutex;
diff --git a/UnixDomainListener.cpp b/UnixDomainListener.cpp
index fda7b4d..730d604 100644
--- a/UnixDomainListener.cpp
+++ b/UnixDomainListener.cpp
@@ -46,7 +46,19 @@ bool UnixDomainListener::Open() {
     addr.sun_family = AF_UNIX;
     _socket_path.copy(addr.sun_path, sizeof(addr.sun_path));
 
-    unlink(_socket_path.c_str());
+    // If the first character is a '@', then this is an abstract socket address
+    // Replace all '@' bytes with null bytes.
+    if (addr.sun_path[0] == '@') {
+        for (int i = 0; i < sizeof(addr.sun_path); i++) {
+            if (addr.sun_path[i] == '@') {
+                addr.sun_path[i] = 0;
+            }
+        }
+    }
+
+    if (addr.sun_path[0] != 0) {
+        unlink(_socket_path.c_str());
+    }
 
     if (bind(lfd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
     {
@@ -55,11 +67,13 @@ bool UnixDomainListener::Open() {
         return false;
     }
 
-    // Only allow process uid access to the socket file
-    if (chmod(_socket_path.c_str(), _socket_file_mode) < 0) {
-        close(lfd);
-        Logger::Error("Inputs: chmod('%s', 0%03o) failed: %s", _socket_path.c_str(), _socket_file_mode, std::strerror(errno));
-        return false;
+    if (addr.sun_path[0] != 0) {
+        // Only allow process uid access to the socket file
+        if (chmod(_socket_path.c_str(), _socket_file_mode) < 0) {
+            close(lfd);
+            Logger::Error("Inputs: chmod('%s', 0%03o) failed: %s", _socket_path.c_str(), _socket_file_mode, std::strerror(errno));
+            return false;
+        }
     }
 
     if (listen(lfd, 5) != 0) {
diff --git a/UnixDomainWriter.cpp b/UnixDomainWriter.cpp
index 1b86e5b..eb1c384 100644
--- a/UnixDomainWriter.cpp
+++ b/UnixDomainWriter.cpp
@@ -36,6 +36,16 @@ bool UnixDomainWriter::Open()
     unaddr.sun_family = AF_UNIX;
     _addr.copy(unaddr.sun_path, sizeof(unaddr.sun_path));
 
+    // If the first character is a '@', then this is an abstract socket address
+    // Replace all '@' bytes with null bytes.
+    if (unaddr.sun_path[0] == '@') {
+        for (int i = 0; i < sizeof(unaddr.sun_path); i++) {
+            if (unaddr.sun_path[i] == '@') {
+                unaddr.sun_path[i] = 0;
+            }
+        }
+    }
+
     int fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
     if (-1 == fd) {
         throw std::system_error(errno, std::system_category(), "socket() failed");