PR31862: debuginfod: client to cache x-debuginfod-* headers

This feature allows the extra http headers from debuginfod to be saved
into the client cache, and also thus replayed to clients.  This way
they can perform IMA verification again, if they like, or a federating
caching intermediate debuginfod server can replay the headers it
received previously from upstream to future downstream.  The headers
are placed adjacent to the payload files .cache/debuginfod/BUILDID/PAYLOAD
as .cache/debuginfod/BUILDID/hdr-PAYLOAD.  They are aged the same
atime-based way.

Testing via an extension of a previous small test, and hand-running both
client & server code under valgrind.  No memcheck errors reported.

Signed-off-by: Frank Ch. Eigler <[email protected]>

2 files changed, 67 insertions, 7 deletions

diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index d89beae9..3c3a88d1 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -569,7 +569,7 @@ debuginfod_clean_cache(debuginfod_client *c,
     return -errno;
 
   regex_t re;
-  const char * pattern = ".*/(metadata.*|[a-f0-9]+(/debuginfo|/executable|/source.*|))$"; /* include dirs */
+  const char * pattern = ".*/(metadata.*|[a-f0-9]+(/hdr.*|/debuginfo|/executable|/source.*|))$"; /* include dirs */
   /* NB: also matches .../section/ subdirs, so extracted section files also get cleaned. */
   if (regcomp (&re, pattern, REG_EXTENDED | REG_NOSUB) != 0)
     return -ENOMEM;
@@ -1777,7 +1777,9 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
   char *cache_miss_path = NULL;
   char *target_cache_dir = NULL;
   char *target_cache_path = NULL;
+  char *target_cachehdr_path = NULL;
   char *target_cache_tmppath = NULL;
+  char *target_cachehdr_tmppath = NULL;
   char suffix[NAME_MAX];
   char build_id_bytes[MAX_BUILD_ID_BYTES * 2 + 1];
   int vfd = c->verbose_fd;
@@ -1912,6 +1914,8 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
      target_cache_path: $HOME/.cache/0123abcd/debuginfo
      target_cache_path: $HOME/.cache/0123abcd/executable-.debug_info
      target_cache_path: $HOME/.cache/0123abcd/source-HASH-#PATH#TO#SOURCE
+     target_cachehdr_path: $HOME/.cache/0123abcd/hdr-debuginfo
+     target_cachehdr_path: $HOME/.cache/0123abcd/hdr-executable...
   */
 
   cache_path = make_cache_path();
@@ -1923,11 +1927,15 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
   xalloc_str (target_cache_dir, "%s/%s", cache_path, build_id_bytes);
   (void) mkdir (target_cache_dir, 0700); // failures with this mkdir would be caught later too
 
-  if (suffix[0] != '\0') /* section, source queries */
+  if (suffix[0] != '\0') { /* section, source queries */ 
     xalloc_str (target_cache_path, "%s/%s-%s", target_cache_dir, type, suffix);
-  else
+    xalloc_str (target_cachehdr_path, "%s/hdr-%s-%s", target_cache_dir, type, suffix);
+  } else {
     xalloc_str (target_cache_path, "%s/%s", target_cache_dir, type);
+    xalloc_str (target_cachehdr_path, "%s/hdr-%s", target_cache_dir, type);
+  }
   xalloc_str (target_cache_tmppath, "%s.XXXXXX", target_cache_path);
+  xalloc_str (target_cachehdr_tmppath, "%s.XXXXXX", target_cachehdr_path);  
 
   /* XXX combine these */
   xalloc_str (interval_path, "%s/%s", cache_path, cache_clean_interval_filename);
@@ -1978,6 +1986,32 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
           /* Success!!!! */
           update_atime(fd);
           rc = fd;
+
+          /* Attempt to transcribe saved headers. */
+          int fdh = open (target_cachehdr_path, O_RDONLY);
+          if (fdh >= 0)
+            {
+              if (fstat (fdh, &st) == 0 && st.st_size > 0)
+                {
+                  c->winning_headers = malloc(st.st_size);
+                  if (NULL != c->winning_headers)
+                    {
+                      ssize_t bytes_read = pread_retry(fdh, c->winning_headers, st.st_size, 0);
+                      if (bytes_read <= 0)
+                        {
+                          free (c->winning_headers);
+                          c->winning_headers = NULL;
+                          (void) unlink (target_cachehdr_path);
+                        }
+                      if (vfd >= 0)
+                        dprintf (vfd, "found %s (bytes=%ld)\n", target_cachehdr_path, (long)bytes_read);
+                    }
+                }
+
+              update_atime (fdh);
+              close (fdh);
+            }
+ 
           goto out;
         }
       else
@@ -2004,12 +2038,12 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
             /* TOCTOU non-problem: if another task races, puts a working
                download or an empty file in its place, unlinking here just
                means WE will try to download again as uncached. */
-            unlink(target_cache_path);
+            (void) unlink(target_cache_path);
         }
     }
   else if (errno == EACCES)
     /* Ensure old 000-permission files are not lingering in the cache. */
-    unlink(target_cache_path);
+    (void) unlink(target_cache_path);
 
   if (section != NULL)
     {
@@ -2409,6 +2443,22 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
       /* Perhaps we need not give up right away; could retry or something ... */
     }
 
+  /* write out the headers, best effort basis */
+  if (c->winning_headers) {
+    int fdh = mkstemp (target_cachehdr_tmppath);
+    if (fdh >= 0) {
+      size_t bytes_to_write = strlen(c->winning_headers)+1; // include \0
+      size_t bytes = pwrite_retry (fdh, c->winning_headers, bytes_to_write, 0);
+      (void) close (fdh);
+      if (bytes == bytes_to_write)
+        (void) rename (target_cachehdr_tmppath, target_cachehdr_path);
+      else
+        (void) unlink (target_cachehdr_tmppath);
+      if (vfd >= 0)
+        dprintf (vfd, "saved %ld bytes of headers to %s\n", (long)bytes, target_cachehdr_path);
+    }
+  }
+  
   /* remove all handles from multi */
   for (int i = 0; i < num_urls; i++)
     {
@@ -2490,8 +2540,11 @@ debuginfod_query_server_by_buildid (debuginfod_client *c,
   if (rc < 0 && target_cache_tmppath != NULL)
     (void)unlink (target_cache_tmppath);
   free (target_cache_tmppath);
-
-  
+  if (rc < 0 && target_cachehdr_tmppath != NULL)
+    (void)unlink (target_cachehdr_tmppath);
+  free (target_cachehdr_tmppath);
+  free (target_cachehdr_path);
+    
   return rc;
 }
 
diff --git a/tests/run-debuginfod-artifact-running.sh b/tests/run-debuginfod-artifact-running.sh
index 8b9aed37..df42957b 100755
--- a/tests/run-debuginfod-artifact-running.sh
+++ b/tests/run-debuginfod-artifact-running.sh
@@ -116,4 +116,11 @@ cmp $filename ${PWD}/prog2.c
 kill $PID1
 wait $PID1
 PID1=0
+
+# PR31862: after killing debuginfod, check that the cached version still exists and holds headers!
+(DEBUGINFOD_VERBOSE=1; export DEBUGINFOD_VERBOSE
+ testrun ${abs_top_builddir}/debuginfod/debuginfod-find -v debuginfo $BUILDID2 2>&1) | tee vlog3
+tempfiles vlog3
+grep -i x-debuginfod vlog3
+
 exit 0