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limits.c
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limits.c
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#include <stdio.h>
#include <stdbool.h>
#include <libgen.h>
#include <unistd.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/user.h>
#include <regex.h>
#include <glib.h>
#include <err.h>
#include "proc.h"
#include "flags.h"
#include "rlim.h"
static void print_usage(const char *name)
{
const char *description =
"Test how COMMAND reacts to reduced resource limits.\n\n"
"\t-t TIMEOUT Kill the process if it takes longer than this.\n"
"\t-b FILTER Load regex (one per line) to filter output.\n"
"\t-o OUTPUT Generate commands to see output in file.\n"
"\t-i INFILE Attach specified file to process stdin.\n"
"\n"
"Example:\n\n"
"\tlimits -b filters.txt -o output -- /usr/bin/sudo";
printf("%s [OPTIONS] [--] COMMAND [ARGS..]\n", name);
puts(description);
return;
}
// This routine reads a list of regex that should be removed from
// the output of programs being tested.
//
// The reason this is necessary is that some programs will add timestamps or
// pids to error messages and we have no way of knowing if this is a new error
// message, or an old one with a new timestamp.
//
// The list should be freed when no longer needed.
static GSList * parse_filterlist_file(const char *filename)
{
GSList *list;
gchar *file;
gchar **patterns;
// Read in the list of regex.
if (g_file_get_contents(filename, &file, NULL, NULL) != true) {
err(EXIT_FAILURE, "failed to open filter pattern file %s", filename);
return NULL;
}
// Split that, one per line.
patterns = g_strsplit(file, "\n", -1);
// We return a linked list of compiled regex.
list = NULL;
// Attempt to compile each patten.
for (guint i = 0; i < g_strv_length(patterns); i++) {
GRegex *r;
g_debug("attempting to parse pattern /%s/", patterns[i]);
// Check if this is a comment.
if (patterns[i][0] == '#' || patterns[i][0] == '\0') {
continue;
}
// Not a comment, compile the regex.
r = g_regex_new(patterns[i], G_REGEX_OPTIMIZE, 0, NULL);
if (r == NULL) {
errx(EXIT_FAILURE, "failed to compile expression %s", patterns[i]);
continue;
}
// It compiled, append to the filter list.
list = g_slist_append(list, r);
}
g_print("file %s contained %d valid filter patterns.\n",
filename,
g_slist_length(list));
cleanup:
// cleanup.
g_strfreev(patterns);
g_free(file);
return list;
}
// Combine the results of an execution into a string.
// Note: checksum is freed.
static gchar *create_output_key(int result, siginfo_t *info, gchar *checksum)
{
gchar *hash = g_strdup_printf("%08X%08X%08X%s",
result,
info->si_status,
info->si_code,
checksum);
g_free(checksum);
return hash;
}
static void check_used_envvars(gchar **argv, gint timeout, GSList *filters)
{
char **envp = g_get_environ();
gchar *origsum;
gchar *testsum;
guint found;
gint result;
siginfo_t siginfo;
g_print("testing what environment variables influence output...\n");
// Record the default output.
result = read_output_subprocess(argv,
envp,
NULL,
&siginfo,
&origsum,
timeout,
filters);
// Calculate checksum.
origsum = create_output_key(result, &siginfo, origsum);
// Scan to see which variables make a difference.
for (gint i = found = 0; i < g_strv_length(envp); i++) {
gchar *saved = envp[i];
envp[i] = envp[0];
envp[0] = saved;
g_debug("testing %s", saved);
result = read_output_subprocess(argv,
&envp[1],
NULL,
&siginfo,
&testsum,
timeout,
filters);
testsum = create_output_key(result, &siginfo, testsum);
if (g_strcmp0(testsum, origsum) != 0) {
gint len = strcspn(saved, "=");
g_print("\t$%.*s\n", len, saved);
found++;
}
g_free(testsum);
}
g_print("found %u variable(s) that change output\n", found);
g_strfreev(envp);
g_free(origsum);
return;
}
static GHashTable *outputmap;
static gint timeout = 1;
static char **envp;
static char *stdinfile = "/dev/null";
int main(int argc, char **argv)
{
struct rlimit limits[RLIMIT_NLIMITS];
GSList *filters = NULL;
gchar *command = NULL;
FILE *logfile = NULL;
int opt;
while ((opt = getopt(argc, argv, "i:t:ho:b:")) != -1) {
switch (opt) {
case 'h':
print_usage(*argv);
return 0;
case 'b':
filters = parse_filterlist_file(optarg);
break;
case 'o':
logfile = fopen(optarg, "w");
fprintf(logfile, "#!/bin/sh\n");
fflush(logfile);
break;
case 't':
timeout = g_ascii_strtoull(optarg, NULL, 0);
break;
case 'i':
stdinfile = optarg;
break;
default:
print_usage(*argv);
return 1;
}
}
if (optind >= argc) {
errx(EXIT_FAILURE, "expected a command to test");
}
// Attach stdin to child processes.
setup_proc_stdin(stdinfile);
// Create a hashtable to store the known outputs.
outputmap = g_hash_table_new_full(g_str_hash, g_str_equal, NULL, g_free);
// Create a copy of the command for logfiles.
command = g_strjoinv(" ", &argv[optind]);
envp = g_get_environ();
// Make any necessary changes to the childs environment.
envp = g_environ_setenv(envp, "MALLOC_CHECK_", "2", false);
check_used_envvars(&argv[optind], timeout, filters);
// For each of the possible resource limits, we try to see if
// it makes the program behave differently.
//
// If it does, we examine it more closely.
for (gint limit = 0; limit < RLIMIT_NLIMITS; limit++) {
gint result;
gint distance;
gchar *origsum;
gchar *testsum;
siginfo_t siginfo;
g_debug("testing limit %d w/granularity %d",
limit,
get_limit_granularity(limit));
// Skip any ignored limits.
if (get_limit_granularity(limit) == 0) {
continue;
}
g_print("searching %s...\n", limit_to_str(limit));
// Initialize limits from our limits.
init_limits_array(limits);
// Record the default output.
result = read_output_subprocess(&argv[optind],
envp,
limits,
&siginfo,
&origsum,
timeout,
filters);
origsum = create_output_key(result, &siginfo, origsum);
g_debug("default output key is %s", origsum);
// Now find a reasonable start point by bisecting it until something
// changes.
while (limits[limit].rlim_cur >>= 1) {
g_print("\t@%#020lx...", limits[limit].rlim_cur);
result = read_output_subprocess(&argv[optind],
envp,
limits,
&siginfo,
&testsum,
timeout,
filters);
testsum = create_output_key(result, &siginfo, testsum);
// Check if this has changed.
if (g_strcmp0(testsum, origsum) != 0) {
// Put it back the way it was.
limits[limit].rlim_cur <<= 1;
// Put it one above to make sure we collect all errors.
limits[limit].rlim_cur++;
// Report that we found a new error.
g_print("different\n");
g_free(testsum);
break;
}
g_free(testsum);
g_print("same\r");
}
// Now we know where to start searching, so we can start reducing it by
// the appropriate granularity. This is needed because for some limits
// it's pointless testing every possible value, because only the
// nearest page is actualy enforced.
// Seed the normal output in the hashtable.
g_hash_table_add(outputmap, origsum);
search:
// Attempt to reduce the limit until we get a different result.
for (distance = 0;
limits[limit].rlim_cur >= get_limit_granularity(limit);
limits[limit].rlim_cur -= get_limit_granularity(limit)) {
gchar *checksum;
// Sometimes things go really slowly, so increase granularity if
// that's the case.
limits[limit].rlim_cur -= MIN(get_limit_granularity(limit)
* (distance / 32),
limits[limit].rlim_cur);
g_print("Testing %s = %#020lx...",
limit_to_str(limit),
limits[limit].rlim_cur);
result = read_output_subprocess(&argv[optind],
envp,
limits,
&siginfo,
&checksum,
timeout,
filters);
checksum = create_output_key(result, &siginfo, checksum);
// Check if this key is known. Note that we don't need to free
// checksum, the GDestroyNotify function in the GHashTable will
// handle it.
if (g_hash_table_add(outputmap, checksum)) {
g_debug("checksum %s was not previously known", checksum);
g_print("new\n");
// If we have a logfile, try to make it a valid shellscript.
if (logfile) {
fprintf(logfile, "%s/runlimit %s %#lx %s < %s\n",
dirname(*argv),
limit_to_str(limit),
limits[limit].rlim_cur,
command,
stdinfile);
fflush(logfile);
}
// Reset how long it's been since we've seen a change.
distance = 0;
// If there are too many outputs, program might be printing
// timestamps or something.
if (g_hash_table_size(outputmap) == 128) {
warnx("There seems to be many different outputs.");
warnx("This is usually a sign you need to use filters.");
}
} else {
g_print("\r");
}
// No need to continue.
if (limits[limit].rlim_cur < get_limit_granularity(limit)) {
break;
}
}
// Make sure we don't finish on a \r
g_print("\n");
}
if (!logfile && g_hash_table_size(outputmap)) {
g_print("Hint: use -o output.sh to generate a test script\n");
}
cleanup:
g_hash_table_destroy(outputmap);
if (logfile)
fclose(logfile);
if (filters)
g_slist_free_full(filters, (GDestroyNotify) g_regex_unref);
if (command)
g_free(command);
if (envp)
g_strfreev(envp);
return 0;
}