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Variables: avoid possible buffer overrun with some "$sent_http_*". The existing logic to evaluate multi header "$sent_http_*" variables, such as $sent_http_cache_control, as previously introduced in 1.23.0, doesn't take into account that one or more elements can be cleared, yet still present in a linked list, pointed to by the next field. Such elements don't contribute to the resulting variable length, an attempt to append a separator for them ends up in out of bounds write. This is not possible with standard modules, though at least one third party module is known to override multi header values this way, so it makes sense to harden the logic. The fix restores a generic boundary check.
author Sergey Kandaurov <pluknet@nginx.com>
date Mon, 01 May 2023 19:16:05 +0400
parents a27e0c7e198c
children
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>

/*
 * declare Profiler interface here because
 * <google/profiler.h> is C++ header file
 */

int ProfilerStart(u_char* fname);
void ProfilerStop(void);
void ProfilerRegisterThread(void);


static void *ngx_google_perftools_create_conf(ngx_cycle_t *cycle);
static ngx_int_t ngx_google_perftools_worker(ngx_cycle_t *cycle);


typedef struct {
    ngx_str_t  profiles;
} ngx_google_perftools_conf_t;


static ngx_command_t  ngx_google_perftools_commands[] = {

    { ngx_string("google_perftools_profiles"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      0,
      offsetof(ngx_google_perftools_conf_t, profiles),
      NULL },

      ngx_null_command
};


static ngx_core_module_t  ngx_google_perftools_module_ctx = {
    ngx_string("google_perftools"),
    ngx_google_perftools_create_conf,
    NULL
};


ngx_module_t  ngx_google_perftools_module = {
    NGX_MODULE_V1,
    &ngx_google_perftools_module_ctx,      /* module context */
    ngx_google_perftools_commands,         /* module directives */
    NGX_CORE_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    ngx_google_perftools_worker,           /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static void *
ngx_google_perftools_create_conf(ngx_cycle_t *cycle)
{
    ngx_google_perftools_conf_t  *gptcf;

    gptcf = ngx_pcalloc(cycle->pool, sizeof(ngx_google_perftools_conf_t));
    if (gptcf == NULL) {
        return NULL;
    }

    /*
     * set by ngx_pcalloc()
     *
     *     gptcf->profiles = { 0, NULL };
     */

    return gptcf;
}


static ngx_int_t
ngx_google_perftools_worker(ngx_cycle_t *cycle)
{
    u_char                       *profile;
    ngx_google_perftools_conf_t  *gptcf;

    gptcf = (ngx_google_perftools_conf_t *)
                ngx_get_conf(cycle->conf_ctx, ngx_google_perftools_module);

    if (gptcf->profiles.len == 0) {
        return NGX_OK;
    }

    profile = ngx_alloc(gptcf->profiles.len + NGX_INT_T_LEN + 2, cycle->log);
    if (profile == NULL) {
        return NGX_OK;
    }

    if (getenv("CPUPROFILE")) {
        /* disable inherited Profiler enabled in master process */
        ProfilerStop();
    }

    ngx_sprintf(profile, "%V.%d%Z", &gptcf->profiles, ngx_pid);

    if (ProfilerStart(profile)) {
        /* start ITIMER_PROF timer */
        ProfilerRegisterThread();

    } else {
        ngx_log_error(NGX_LOG_CRIT, cycle->log, ngx_errno,
                      "ProfilerStart(%s) failed", profile);
    }

    ngx_free(profile);

    return NGX_OK;
}


/* ProfilerStop() is called on Profiler destruction */