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input validation and removal of unsafe numeric parsing #628

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bacde31
input validation and removal of unsafe numeric parsing in balancer-ma…
metsw24-max Apr 6, 2026
d4d4478
Address review nits: declare ival once per scope, drop redundant incl…
metsw24-max Jul 18, 2026
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113 changes: 91 additions & 22 deletions modules/proxy/mod_proxy_balancer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,9 @@
#include "apr_escape.h"
#include "mod_watchdog.h"

#include <errno.h>
#include <stdlib.h>

@notroj notroj Jul 17, 2026

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<errno.h> should be inherited via APR headers already, are these really needed?

@metsw24-max metsw24-max Jul 18, 2026

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You're right, both come in via the APR headers already. Removed them and the module still builds cleanly with -Wall.


static const char *balancer_mutex_type = "proxy-balancer-shm";
ap_slotmem_provider_t *storage = NULL;

Expand All @@ -40,6 +43,54 @@ static APR_OPTIONAL_FN_TYPE(hc_show_exprs) *hc_show_exprs_f = NULL;
static APR_OPTIONAL_FN_TYPE(hc_select_exprs) *hc_select_exprs_f = NULL;
static APR_OPTIONAL_FN_TYPE(hc_valid_expr) *hc_valid_expr_f = NULL;

static int balancer_parse_int(const char *val, int min, int max, int *result)
{
apr_int64_t parsed;
char *end = NULL;

if (!val || !*val) {
return 0;
}

errno = 0;
parsed = apr_strtoi64(val, &end, 10);
if (errno == ERANGE || end == val || *end != '\0') {
return 0;
}

if (parsed < min || parsed > max) {
return 0;
}

*result = (int)parsed;
return 1;
}

static int balancer_parse_lbfactor(const char *val, int *result)
{
char *end = NULL;
double parsed;
double scaled;

if (!val || !*val) {
return 0;
}

errno = 0;
parsed = strtod(val, &end);
if (errno == ERANGE || end == val || *end != '\0') {
return 0;
}

scaled = parsed * 100.0;
if (scaled < 100.0 || scaled > 10000.0) {
return 0;
}

*result = (int)scaled;
return 1;
}


/*
* Register our mutex type before the config is read so we
Expand Down Expand Up @@ -1114,9 +1165,7 @@ static int balancer_process_balancer_worker(request_rec *r, proxy_server_conf *c

if ((val = apr_table_get(params, "w_lf"))) {
int ival;
double fval = atof(val);
ival = fval * 100.0;
if (ival >= 100 && ival <= 10000) {
if (balancer_parse_lbfactor(val, &ival)) {
wsel->s->lbfactor = ival;
if (bsel)
recalc_factors(bsel);
Expand All @@ -1139,29 +1188,50 @@ static int balancer_process_balancer_worker(request_rec *r, proxy_server_conf *c
* on that # character, since the character == the flag
*/
if ((val = apr_table_get(params, "w_status_I"))) {
ap_proxy_set_wstatus(PROXY_WORKER_IGNORE_ERRORS_FLAG, atoi(val), wsel);
int ival;

@notroj notroj Jul 17, 2026

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coding style nit, declaring int ival in every single branch here is clearly making the code worse / harder to read, so move it up a context and just declare it once.

@metsw24-max metsw24-max Jul 18, 2026

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Done, moved it up to the enclosing block so it's declared once, and dropped the per-branch declarations.

if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_IGNORE_ERRORS_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_N"))) {
ap_proxy_set_wstatus(PROXY_WORKER_DRAIN_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_DRAIN_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_D"))) {
ap_proxy_set_wstatus(PROXY_WORKER_DISABLED_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_DISABLED_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_H"))) {
ap_proxy_set_wstatus(PROXY_WORKER_HOT_STANDBY_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_HOT_STANDBY_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_R"))) {
ap_proxy_set_wstatus(PROXY_WORKER_HOT_SPARE_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_HOT_SPARE_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_S"))) {
ap_proxy_set_wstatus(PROXY_WORKER_STOPPED_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_STOPPED_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_status_C"))) {
ap_proxy_set_wstatus(PROXY_WORKER_HC_FAIL_FLAG, atoi(val), wsel);
int ival;
if (balancer_parse_int(val, 0, 1, &ival)) {
ap_proxy_set_wstatus(PROXY_WORKER_HC_FAIL_FLAG, ival, wsel);
}
}
if ((val = apr_table_get(params, "w_ls"))) {
int ival = atoi(val);
if (ival >= 0 && ival <= 99) {
int ival;
if (balancer_parse_int(val, 0, 99, &ival)) {
wsel->s->lbset = ival;
}
}
Expand All @@ -1174,14 +1244,14 @@ static int balancer_process_balancer_worker(request_rec *r, proxy_server_conf *c
}
}
if ((val = apr_table_get(params, "w_hp"))) {
int ival = atoi(val);
if (ival >= 1) {
int ival;
if (balancer_parse_int(val, 1, APR_INT32_MAX, &ival)) {
wsel->s->passes = ival;
}
}
if ((val = apr_table_get(params, "w_hf"))) {
int ival = atoi(val);
if (ival >= 1) {
int ival;
if (balancer_parse_int(val, 1, APR_INT32_MAX, &ival)) {
wsel->s->fails = ival;
}
}
Expand Down Expand Up @@ -1234,21 +1304,20 @@ static int balancer_process_balancer_worker(request_rec *r, proxy_server_conf *c
}
}
if ((val = apr_table_get(params, "b_tmo"))) {
ival = atoi(val);
if (ival >= 0 && ival <= 7200) { /* 2 hrs enuff? */
if (balancer_parse_int(val, 0, 7200, &ival)) { /* 2 hrs enuff? */
bsel->s->timeout = apr_time_from_sec(ival);
}
}
if ((val = apr_table_get(params, "b_max"))) {
ival = atoi(val);
if (ival >= 0 && ival <= 99) {
if (balancer_parse_int(val, 0, 99, &ival)) {
bsel->s->max_attempts = ival;
bsel->s->max_attempts_set = 1;
}
}
if ((val = apr_table_get(params, "b_sforce"))) {
ival = atoi(val);
bsel->s->sticky_force = (ival != 0);
if (balancer_parse_int(val, 0, 1, &ival)) {
bsel->s->sticky_force = (ival != 0);
}
}
if ((val = apr_table_get(params, "b_ss")) && *val) {
if (strlen(val) < (sizeof(bsel->s->sticky_path)-1)) {
Expand Down