fips: Clarify what to be hashed for the integrity check.

* src/fips.c (get_file_offset): Compute the maximum offset
of segments.
* src/gen-note-integrity.sh: Likewise.

--

The result is same (in current format of ELF program).
Semantics is more clear.  It hashes:

  - From the start of shared library file,
  - fixed up the ELF header to exclude link-time information,
  - up to the last segment.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

2 files changed, 23 insertions, 17 deletions

diff --git a/src/fips.c b/src/fips.c
index d798d577..89f8204b 100644
--- a/src/fips.c
+++ b/src/fips.c
@@ -595,7 +595,7 @@ run_random_selftests (void)
 
 /*
  * In the ELF file opened as FP, fill the ELF header to the pointer
- * EHDR_P, determine the offset of last loadable segment in R_OFFSET.
+ * EHDR_P, determine the maximum offset of segments in R_OFFSET.
  * Also, find the section which contains the hmac value and return it
  * in HMAC.  Rewinds FP to the beginning on success.
  */
@@ -624,24 +624,22 @@ get_file_offset (FILE *fp, ElfW (Ehdr) *ehdr_p,
   if (fseek (fp, ehdr_p->e_phoff, SEEK_SET) != 0)
     return gpg_error_from_syserror ();
 
-  /* Iterate over the program headers, determine the last loadable
-     segment.  */
+  /* Iterate over the program headers, determine the last offset of
+     segments.  */
   for (i = 0; i < ehdr_p->e_phnum; i++)
     {
+      unsigned long off;
+
       if (fread (&phdr, sizeof (phdr), 1, fp) != 1)
         return gpg_error_from_syserror ();
 
-      if (phdr.p_type == PT_PHDR)
-        continue;
-
-      if (phdr.p_type != PT_LOAD)
-        break;
-
-      off_segment = phdr.p_offset + phdr.p_filesz;
+      off = phdr.p_offset + phdr.p_filesz;
+      if (off_segment < off)
+        off_segment = off;
     }
 
   if (!off_segment)
-    /* The segment not found in the file */
+    /* No segment found in the file */
     return gpg_error (GPG_ERR_INV_OBJ);
 
   /* The section header entry size should match the size of the shdr struct */
diff --git a/src/gen-note-integrity.sh b/src/gen-note-integrity.sh
index 878d7095..50071bf5 100755
--- a/src/gen-note-integrity.sh
+++ b/src/gen-note-integrity.sh
@@ -95,21 +95,29 @@ else
     dd ibs=1         count=6  if=/dev/zero status=none
 fi > header-fixed.bin
 
-# Compute the end of loadable segment.
+#
+# Compute the end of segments, and emit the COUNT to read
+# (For each segment in program headers, calculate the offset
+#  and select the maximum)
 #
 # This require computation in hexadecimal, and GNU awk needs
 # --non-decimal-data option
 #
-OFFSET=$($READELF --wide --program-headers $FILE | \
-         $AWK $AWK_OPTION "/^  LOAD/ { offset=\$2+\$5-$HEADER_SIZE }\
-END { print offset}")
+COUNT=$($READELF --wide --program-headers $FILE | \
+         $AWK $AWK_OPTION \
+"BEGIN { max_offset=0 }
+/^\$/ { if (program_headers_start) program_headers_end=1 }
+(program_headers_start && !program_headers_end) { offset = \$2 + \$5 }
+(max_offset < offset) { max_offset = offset }
+/^  Type/ { program_headers_start=1 }
+END { print max_offset- $HEADER_SIZE }")
 
 #
-# Feed the header fixed and loadable segments to HMAC256
+# Feed the header fixed and all segments to HMAC256
 # to generate hmac hash of the FILE
 #
 (cat header-fixed.bin; \
- dd ibs=1 skip=$HEADER_SIZE count=$OFFSET if=$FILE status=none) \
+ dd ibs=1 skip=$HEADER_SIZE count=$COUNT if=$FILE status=none) \
  | ./hmac256 --stdkey --binary
 
 rm -f header-fixed.bin