[PATCH] debuginfod: Check the DEBUGINFOD_URLS environment variable early in client.

[Mark Wielaard]

If the debuginfod-client isn't configured we should do as little
as possible. Simply return early with ENOSYS if no servers are
configured. This means we won't check

This does change the behavior of the debuginfod_find calls slightly.
Previously we would setup and check the cache if the given build-id
was valid. Which might have provided a result if an earlier client
had run with the same cache and valid server URLs which knew about
that particular build-id. Now we don't return any cached results
unless at least one server is configured.

This prevents selinux errors when the library is used in a confined
setup.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 debuginfod/ChangeLog           |  5 +++++
 debuginfod/debuginfod-client.c | 20 +++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 10b6bfed..bb7c5687 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-09  Mark Wielaard  <mark@klomp.org>
+
+	* debuginfod-client.c (debuginfod_query_server): Check
+	server_urls_envvar early.
+
 2019-12-03  Mark Wielaard  <mark@klomp.org>
 
 	* debuginfod-client.c (debuginfod_query_server): Use separate
diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index 302ea2dc..ab7b4e13 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -301,6 +301,16 @@ debuginfod_query_server (debuginfod_client *c,
   char target_cache_tmppath[PATH_MAX*5];
   char suffix[PATH_MAX*2];
   char build_id_bytes[MAX_BUILD_ID_BYTES * 2 + 1];
+  int rc;
+
+  /* Is there any server we can query?  If not, don't do any work,
+     just return with ENOSYS.  Don't even access the cache.  */
+  urls_envvar = getenv(server_urls_envvar);
+  if (urls_envvar == NULL || urls_envvar[0] == '\0')
+    {
+      rc = -ENOSYS;
+      goto out;
+    }
 
   /* Copy lowercase hex representation of build_id into buf.  */
   if ((build_id_len >= MAX_BUILD_ID_BYTES) ||
@@ -373,7 +383,7 @@ debuginfod_query_server (debuginfod_client *c,
   /* XXX combine these */
   snprintf(interval_path, sizeof(interval_path), "%s/%s", cache_path, cache_clean_interval_filename);
   snprintf(maxage_path, sizeof(maxage_path), "%s/%s", cache_path, cache_max_unused_age_filename);
-  int rc = debuginfod_init_cache(cache_path, interval_path, maxage_path);
+  rc = debuginfod_init_cache(cache_path, interval_path, maxage_path);
   if (rc != 0)
     goto out;
   rc = debuginfod_clean_cache(c, cache_path, interval_path, maxage_path);
@@ -390,14 +400,6 @@ debuginfod_query_server (debuginfod_client *c,
       return fd;
     }
 
-
-  urls_envvar = getenv(server_urls_envvar);
-  if (urls_envvar == NULL || urls_envvar[0] == '\0')
-    {
-      rc = -ENOSYS;
-      goto out;
-    }
-
   if (getenv(server_timeout_envvar))
     server_timeout = atoi (getenv(server_timeout_envvar));
 
-- 
2.18.1