Re: [rfc] [patch] PR28204: debuginfod ima signature verification

[Frank Ch. Eigler]

Hi -

On Tue, Apr 16, 2024 at 06:15:00PM -0400, Frank Ch. Eigler wrote:
> The following is the candidate patch for the basic functionality.
> It's been corrected for whitespace & error codes, given more complete
> docs and commit message.  See also the users/fche/try-bz2824f branch.
> [...]

ping

- FChE

[PATCH] readelf: Fix printing of DW_FORM_strx and DW_MACRO parsing

[Mark Wielaard]

print_form_data didn't take the offset_len (4 or 8 bytes) into account
causing the wrong entry to be read from .debug_str_offsets.
print_debug_macro_section did sanity checking before calling
print_form_data, which does sanity checking itself. The sanity check
for DW_FORM_strx was wrong in print_debug_macro_section (but correct
in print_form_data).

Add a new testfile for run-readelf-macro.sh, this one compiled with
clang -gdwarf-5 -fdebug-macro.

  * src/readelf.c (print_form_data): Multiply by offset_len for
  strx_val.
  (print_debug_macro_section): Remove sanity checks before calling
  print_form_data.
  * tests/testfileclangmacro.bz2: New testfile.
  * tests/Makefile.am (EXTRA_DIST): Add testfileclangmacro.bz2.
  * tests/run-readelf-macro.sh: Add testfileclangmacro output.

Signed-off-by: Mark Wielaard 
---
 src/readelf.c|  13 +-
 tests/Makefile.am|   2 +-
 tests/run-readelf-macro.sh   | 817 ++-
 tests/testfileclangmacro.bz2 | Bin 0 -> 7985 bytes
 4 files changed, 820 insertions(+), 12 deletions(-)
 create mode 100755 tests/testfileclangmacro.bz2

diff --git a/src/readelf.c b/src/readelf.c
index 0e931184ed38..c945b371966f 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -8869,11 +8869,12 @@ print_form_data (Dwarf *dbg, int form, const unsigned 
char *readp,
 strx_val:
   data = dbg->sectiondata[IDX_debug_str_offsets];
   if (data == NULL
- || data->d_size - str_offsets_base < val)
+ || data->d_size - str_offsets_base < val * offset_len)
str = "???";
   else
{
- const unsigned char *strreadp = data->d_buf + str_offsets_base + val;
+ const unsigned char *strreadp = (data->d_buf + str_offsets_base
+  + val * offset_len);
  const unsigned char *strreadendp = data->d_buf + data->d_size;
  if ((size_t) (strreadendp - strreadp) < offset_len)
str = "???";
@@ -10853,8 +10854,6 @@ print_debug_macro_section (Dwfl_Module *dwflmod 
__attribute__ ((unused)),
 
case DW_MACRO_define_sup:
  get_uleb128 (u128, readp, readendp);
- if (readp + offset_len > readendp)
-   goto invalid_data;
  printf ("%*s#define ", level, "");
  readp =  print_form_data (dbg, DW_FORM_strp_sup,
readp, readendp, offset_len,
@@ -10864,8 +10863,6 @@ print_debug_macro_section (Dwfl_Module *dwflmod 
__attribute__ ((unused)),
 
case DW_MACRO_undef_sup:
  get_uleb128 (u128, readp, readendp);
- if (readp + offset_len > readendp)
-   goto invalid_data;
  printf ("%*s#undef ", level, "");
  readp =  print_form_data (dbg, DW_FORM_strp_sup,
readp, readendp, offset_len,
@@ -10887,8 +10884,6 @@ print_debug_macro_section (Dwfl_Module *dwflmod 
__attribute__ ((unused)),
 
case DW_MACRO_define_strx:
  get_uleb128 (u128, readp, readendp);
- if (readp + offset_len > readendp)
-   goto invalid_data;
  printf ("%*s#define ", level, "");
  readp =  print_form_data (dbg, DW_FORM_strx,
readp, readendp, offset_len,
@@ -10898,8 +10893,6 @@ print_debug_macro_section (Dwfl_Module *dwflmod 
__attribute__ ((unused)),
 
case DW_MACRO_undef_strx:
  get_uleb128 (u128, readp, readendp);
- if (readp + offset_len > readendp)
-   goto invalid_data;
  printf ("%*s#undef ", level, "");
  readp =  print_form_data (dbg, DW_FORM_strx,
readp, readendp, offset_len,
diff --git a/tests/Makefile.am b/tests/Makefile.am
index b7fb72384f32..46f553a9b991 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -378,7 +378,7 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh run-ar.sh \
 testfile46.bz2 testfile47.bz2 testfile48.bz2 testfile48.debug.bz2 \
 testfile49.bz2 testfile50.bz2 testfile51.bz2 \
 testfile-macros-0xff.bz2 \
-run-readelf-macro.sh testfilemacro.bz2 \
+run-readelf-macro.sh testfilemacro.bz2 testfileclangmacro.bz2 \
 run-readelf-loc.sh testfileloc.bz2 \
 splitdwarf4-not-split4.dwo.bz2 \
 testfile-splitdwarf4-not-split4.debug.bz2 \
diff --git a/tests/run-readelf-macro.sh b/tests/run-readelf-macro.sh
index 8b17f7da6e05..92401b59ff35 100755
--- a/tests/run-readelf-macro.sh
+++ b/tests/run-readelf-macro.sh
@@ -342,4 +342,819 @@ DWARF section [32] '.debug_macro' at offset 0x2480:
 
 EOF
 
-exit 0
+# Same sources as above, but now using clang
+# gcc -g3 -c hello.c
+# gcc -g3 -c world.c
+# gcc -g3 -o testfilemacro hello.o world.o
+
+# clang -gdwarf-5 -fdebug-macro -c hello.c
+# clang -gdwarf-5 -fdebug-macro -c world.c
+# clang