Re: [PATCH v3 14/19] elf: Ignore loader debug env vars for setuid

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 20/11/23 19:57, Siddhesh Poyarekar wrote:
> On 2023-11-06 15:25, Adhemerval Zanella wrote:
>> Loader already ignores LD_DEBUG, LD_DEBUG_OUTPUT, and
>> LD_TRACE_LOADED_OBJECTS. Both LD_WARN and LD_VERBOSE are similar to
>> LD_DEBUG, in the sense they enable additional checks and debug
>> information, so it makes sense to disable them.
>>
>> Checked on x86_64-linux-gnu.
>> ---
> 
> Maybe also put it in unsecvars.h?

Ack.

> 
>>   elf/rtld.c           | 22 ++++++++++++++--------
>>   elf/tst-env-setuid.c |  2 ++
>>   2 files changed, 16 insertions(+), 8 deletions(-)
>>
>> diff --git a/elf/rtld.c b/elf/rtld.c
>> index a09cf2a9df..e7f90d37e7 100644
>> --- a/elf/rtld.c
>> +++ b/elf/rtld.c
>> @@ -2552,13 +2552,15 @@ process_envvars (struct dl_main_state *state)
>>       {
>>       case 4:
>>         /* Warning level, verbose or not.  */
>> -      if (memcmp (envline, "WARN", 4) == 0)
>> +      if (!__libc_enable_secure
>> +          && memcmp (envline, "WARN", 4) == 0)
>>           GLRO(dl_verbose) = envline[5] != '\0';
>>         break;
>>         case 5:
>>         /* Debugging of the dynamic linker?  */
>> -      if (memcmp (envline, "DEBUG", 5) == 0)
>> +      if (!__libc_enable_secure
>> +          && memcmp (envline, "DEBUG", 5) == 0)
>>           {
>>             process_dl_debug (state, &envline[6]);
>>             break;
>> @@ -2569,7 +2571,8 @@ process_envvars (struct dl_main_state *state)
>>         case 7:
>>         /* Print information about versions.  */
>> -      if (memcmp (envline, "VERBOSE", 7) == 0)
>> +      if (!__libc_enable_secure
>> +          && memcmp (envline, "VERBOSE", 7) == 0)
>>           {
>>             state->version_info = envline[8] != '\0';
>>             break;
>> @@ -2625,7 +2628,8 @@ process_envvars (struct dl_main_state *state)
>>           }
>>           /* Where to place the profiling data file.  */
>> -      if (memcmp (envline, "DEBUG_OUTPUT", 12) == 0)
>> +      if (!__libc_enable_secure
>> +          && memcmp (envline, "DEBUG_OUTPUT", 12) == 0)
>>           {
>>             debug_output = &envline[13];
>>             break;
>> @@ -2646,7 +2650,8 @@ process_envvars (struct dl_main_state *state)
>>         case 20:
>>         /* The mode of the dynamic linker can be set.  */
>> -      if (memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0)
>> +      if (!__libc_enable_secure
>> +          && memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0)
>>           {
>>             state->mode = rtld_mode_trace;
>>             state->mode_trace_program
>> @@ -2668,9 +2673,10 @@ process_envvars (struct dl_main_state *state)
>>       }
>>         while (*nextp != '\0');
>>   -      GLRO(dl_debug_mask) = 0;
>> -
>> -      if (state->mode != rtld_mode_normal)
>> +      if (GLRO(dl_debug_mask) != 0
>> +      || GLRO(dl_verbose) != 0
>> +      || state->mode != rtld_mode_normal
>> +      || state->version_info)
>>       _exit (5);
>>       }
>>     /* If we have to run the dynamic linker in debugging mode and the
>> diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
>> index 76b8e1fb45..dcf213a4cd 100644
>> --- a/elf/tst-env-setuid.c
>> +++ b/elf/tst-env-setuid.c
>> @@ -59,6 +59,8 @@ static const struct envvar_t filtered_envvars[] =
>>     { "MALLOC_TRACE",            FILTERED_VALUE },
>>     { "MALLOC_TRIM_THRESHOLD_",  FILTERED_VALUE },
>>     { "RES_OPTIONS",             FILTERED_VALUE },
>> +  { "LD_DEBUG",                "all" },
>> +  { "LD_DEBUG_OUTPUT",         "/tmp/some-file" },
>>   };
>>     static const struct envvar_t unfiltered_envvars[] =