use default sock path if $OIDC_SOCK not set

CHANGELOG.md

@@ -36,6 +36,8 @@ This did not work as intended. We made the following changes:
 ### Enhancements
 
 - `oidc-add` can now also take an issuer url to load the default account for this issuer, i.e. `oidc-add <issuer_url>`
+- If no socket path is set a default path is tried. The default path
+  is `$TMPDIR/oidc-agent-service-$UID/oidc-agent.sock`, this is the path used by `oidc-agent-service`
 
 ### Bugfixes
 

src/ipc/ipc.c

@@ -32,6 +32,12 @@
 
 #ifndef MINGW
 
+char* defaultSocketPath() {
+  const char* tmp = getenv("TMPDIR") ?: "/tmp";
+  uid_t       uid = getuid();
+  return oidc_sprintf("%s/oidc-agent-service-%d/oidc-agent.sock", tmp, uid);
+}
+
 oidc_error_t initConnectionWithoutPath(struct connection* con, int isServer,
                                        int tcp) {
   con->server     = secAlloc(sizeof(struct sockaddr_un));
@@ -115,15 +121,24 @@ oidc_error_t ipc_client_init(struct connection* con, unsigned char remote) {
 #else
   const char* env_var_name =
       remote ? OIDC_REMOTE_SOCK_ENV_NAME : OIDC_SOCK_ENV_NAME;
+  unsigned char usedDefault = 0;
 #ifdef ANY_MSYS
   char* path = getRegistryValue(env_var_name);
 #else
   char* path = oidc_strcopy(getenv(env_var_name));
+  if (path == NULL) {
+    path        = defaultSocketPath();
+    usedDefault = 1;
+  }
 #endif
   if (path == NULL) {
-    char* err = oidc_sprintf("Could not get the socket path from env var '%s'. "
-                             "Have you set the env var?\n",
-                             env_var_name);
+    char* err = oidc_sprintf(
+        "Could not get the socket path from env var '%s'%s. "
+        "Have you set the env var?\nIs a agent running?\n",
+        env_var_name,
+        usedDefault
+            ? " and could not connect to default oidc-agent-service path"
+            : "");
     logger(WARNING, "Could not get the socket path from env var '%s'",
            env_var_name);
     oidc_seterror(err);

src/ipc/ipc.h

@@ -13,6 +13,8 @@
 
 #include "utils/oidc_error.h"
 
+char* defaultSocketPath();
+
 #ifndef MINGW
 oidc_error_t initConnectionWithoutPath(struct connection*, int, int);
 oidc_error_t initConnectionWithPath(struct connection*, const char*);

src/oidc-gen/gen_handler.c

@@ -19,6 +19,7 @@
 #include "defines/oidc_values.h"
 #include "defines/settings.h"
 #include "ipc/cryptCommunicator.h"
+#include "ipc/ipc.h"
 #include "oidc-agent/oidc/device_code.h"
 #include "oidc-gen/device_code.h"
 #include "oidc-gen/gen_consenter.h"
@@ -321,7 +322,8 @@ void handleCodeExchange(const struct arguments* arguments) {
 #ifdef __MSYS__
     socket_path = getRegistryValue(OIDC_SOCK_ENV_NAME);
 #else
-    socket_path = oidc_strcopy(getenv(OIDC_SOCK_ENV_NAME));
+    socket_path =
+        oidc_strcopy(getenv(OIDC_SOCK_ENV_NAME)) ?: defaultSocketPath();
 #endif
     if (socket_path == NULL) {
       printError("Socket path not encoded in url state and not available from "