Mercurial > hg > nginx
view src/http/modules/ngx_http_secure_link_module.c @ 7094:c7d4017c8876
Secure link: fixed stack buffer overflow.
When secure link checksum has length of 23 or 24 bytes, decoded base64 value
could occupy 17 or 18 bytes which is more than 16 bytes previously allocated
for it on stack. The buffer overflow does not have any security implications
since only one local variable was corrupted and this variable was not used in
this case.
The fix is to increase buffer size up to 18 bytes. Useless buffer size
initialization is removed as well.
author | Roman Arutyunyan <arut@nginx.com> |
---|---|
date | Tue, 22 Aug 2017 21:22:59 +0300 |
parents | d89442dab4d1 |
children | bdd4d89370a7 |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_http.h> #include <ngx_md5.h> typedef struct { ngx_http_complex_value_t *variable; ngx_http_complex_value_t *md5; ngx_str_t secret; } ngx_http_secure_link_conf_t; typedef struct { ngx_str_t expires; } ngx_http_secure_link_ctx_t; static ngx_int_t ngx_http_secure_link_old_variable(ngx_http_request_t *r, ngx_http_secure_link_conf_t *conf, ngx_http_variable_value_t *v, uintptr_t data); static ngx_int_t ngx_http_secure_link_expires_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data); static void *ngx_http_secure_link_create_conf(ngx_conf_t *cf); static char *ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent, void *child); static ngx_int_t ngx_http_secure_link_add_variables(ngx_conf_t *cf); static ngx_command_t ngx_http_secure_link_commands[] = { { ngx_string("secure_link"), NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1, ngx_http_set_complex_value_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_secure_link_conf_t, variable), NULL }, { ngx_string("secure_link_md5"), NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1, ngx_http_set_complex_value_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_secure_link_conf_t, md5), NULL }, { ngx_string("secure_link_secret"), NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1, ngx_conf_set_str_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_secure_link_conf_t, secret), NULL }, ngx_null_command }; static ngx_http_module_t ngx_http_secure_link_module_ctx = { ngx_http_secure_link_add_variables, /* preconfiguration */ NULL, /* postconfiguration */ NULL, /* create main configuration */ NULL, /* init main configuration */ NULL, /* create server configuration */ NULL, /* merge server configuration */ ngx_http_secure_link_create_conf, /* create location configuration */ ngx_http_secure_link_merge_conf /* merge location configuration */ }; ngx_module_t ngx_http_secure_link_module = { NGX_MODULE_V1, &ngx_http_secure_link_module_ctx, /* module context */ ngx_http_secure_link_commands, /* module directives */ NGX_HTTP_MODULE, /* module type */ NULL, /* init master */ NULL, /* init module */ NULL, /* init process */ NULL, /* init thread */ NULL, /* exit thread */ NULL, /* exit process */ NULL, /* exit master */ NGX_MODULE_V1_PADDING }; static ngx_str_t ngx_http_secure_link_name = ngx_string("secure_link"); static ngx_str_t ngx_http_secure_link_expires_name = ngx_string("secure_link_expires"); static ngx_int_t ngx_http_secure_link_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data) { u_char *p, *last; ngx_str_t val, hash; time_t expires; ngx_md5_t md5; ngx_http_secure_link_ctx_t *ctx; ngx_http_secure_link_conf_t *conf; u_char hash_buf[18], md5_buf[16]; conf = ngx_http_get_module_loc_conf(r, ngx_http_secure_link_module); if (conf->secret.data) { return ngx_http_secure_link_old_variable(r, conf, v, data); } if (conf->variable == NULL || conf->md5 == NULL) { goto not_found; } if (ngx_http_complex_value(r, conf->variable, &val) != NGX_OK) { return NGX_ERROR; } ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "secure link: \"%V\"", &val); last = val.data + val.len; p = ngx_strlchr(val.data, last, ','); expires = 0; if (p) { val.len = p++ - val.data; expires = ngx_atotm(p, last - p); if (expires <= 0) { goto not_found; } ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_secure_link_ctx_t)); if (ctx == NULL) { return NGX_ERROR; } ngx_http_set_ctx(r, ctx, ngx_http_secure_link_module); ctx->expires.len = last - p; ctx->expires.data = p; } if (val.len > 24) { goto not_found; } hash.data = hash_buf; if (ngx_decode_base64url(&hash, &val) != NGX_OK) { goto not_found; } if (hash.len != 16) { goto not_found; } if (ngx_http_complex_value(r, conf->md5, &val) != NGX_OK) { return NGX_ERROR; } ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "secure link md5: \"%V\"", &val); ngx_md5_init(&md5); ngx_md5_update(&md5, val.data, val.len); ngx_md5_final(md5_buf, &md5); if (ngx_memcmp(hash_buf, md5_buf, 16) != 0) { goto not_found; } v->data = (u_char *) ((expires && expires < ngx_time()) ? "0" : "1"); v->len = 1; v->valid = 1; v->no_cacheable = 0; v->not_found = 0; return NGX_OK; not_found: v->not_found = 1; return NGX_OK; } static ngx_int_t ngx_http_secure_link_old_variable(ngx_http_request_t *r, ngx_http_secure_link_conf_t *conf, ngx_http_variable_value_t *v, uintptr_t data) { u_char *p, *start, *end, *last; size_t len; ngx_int_t n; ngx_uint_t i; ngx_md5_t md5; u_char hash[16]; p = &r->unparsed_uri.data[1]; last = r->unparsed_uri.data + r->unparsed_uri.len; while (p < last) { if (*p++ == '/') { start = p; goto md5_start; } } goto not_found; md5_start: while (p < last) { if (*p++ == '/') { end = p - 1; goto url_start; } } goto not_found; url_start: len = last - p; if (end - start != 32 || len == 0) { goto not_found; } ngx_md5_init(&md5); ngx_md5_update(&md5, p, len); ngx_md5_update(&md5, conf->secret.data, conf->secret.len); ngx_md5_final(hash, &md5); for (i = 0; i < 16; i++) { n = ngx_hextoi(&start[2 * i], 2); if (n == NGX_ERROR || n != hash[i]) { goto not_found; } } v->len = len; v->valid = 1; v->no_cacheable = 0; v->not_found = 0; v->data = p; return NGX_OK; not_found: v->not_found = 1; return NGX_OK; } static ngx_int_t ngx_http_secure_link_expires_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data) { ngx_http_secure_link_ctx_t *ctx; ctx = ngx_http_get_module_ctx(r, ngx_http_secure_link_module); if (ctx) { v->len = ctx->expires.len; v->valid = 1; v->no_cacheable = 0; v->not_found = 0; v->data = ctx->expires.data; } else { v->not_found = 1; } return NGX_OK; } static void * ngx_http_secure_link_create_conf(ngx_conf_t *cf) { ngx_http_secure_link_conf_t *conf; conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_secure_link_conf_t)); if (conf == NULL) { return NULL; } /* * set by ngx_pcalloc(): * * conf->variable = NULL; * conf->md5 = NULL; * conf->secret = { 0, NULL }; */ return conf; } static char * ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent, void *child) { ngx_http_secure_link_conf_t *prev = parent; ngx_http_secure_link_conf_t *conf = child; if (conf->secret.data) { if (conf->variable || conf->md5) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "\"secure_link_secret\" cannot be mixed with " "\"secure_link\" and \"secure_link_md5\""); return NGX_CONF_ERROR; } return NGX_CONF_OK; } if (conf->variable == NULL) { conf->variable = prev->variable; } if (conf->md5 == NULL) { conf->md5 = prev->md5; } if (conf->variable == NULL && conf->md5 == NULL) { conf->secret = prev->secret; } return NGX_CONF_OK; } static ngx_int_t ngx_http_secure_link_add_variables(ngx_conf_t *cf) { ngx_http_variable_t *var; var = ngx_http_add_variable(cf, &ngx_http_secure_link_name, 0); if (var == NULL) { return NGX_ERROR; } var->get_handler = ngx_http_secure_link_variable; var = ngx_http_add_variable(cf, &ngx_http_secure_link_expires_name, 0); if (var == NULL) { return NGX_ERROR; } var->get_handler = ngx_http_secure_link_expires_variable; return NGX_OK; }