From 1be112f371f860feab290cb333792c52e4e23c7c Mon Sep 17 00:00:00 2001 From: Ben Fuhrmannek Date: Tue, 19 Apr 2022 12:43:18 +0200 Subject: allow file:// prefix in include() wich readonly_exec mode --- src/sp_execute.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'src/sp_execute.c') diff --git a/src/sp_execute.c b/src/sp_execute.c index f1ed8d0..9cf44e1 100644 --- a/src/sp_execute.c +++ b/src/sp_execute.c @@ -17,9 +17,9 @@ ZEND_COLD static inline void terminate_if_writable(const char *filename) { sp_log_request(config_ro_exec->dump, config_ro_exec->textual_representation); } if (true == config_ro_exec->simulation) { - sp_log_simulation("readonly_exec", "Attempted execution of a writable file (%s).", filename); + sp_log_simulation("readonly_exec", "Attempted execution of a writable file (%s)", filename); } else { - sp_log_drop("readonly_exec", "Attempted execution of a writable file (%s).", filename); + sp_log_drop("readonly_exec", "Attempted execution of a writable file (%s)", filename); } } else { if (EACCES != errno) { @@ -224,13 +224,18 @@ static inline void sp_stream_open_checks(zend_string *zend_filename, zend_file_h return; } - // zend_string *zend_filename = zend_string_init(filename, strlen(filename), 0); const HashTable *disabled_functions_hooked = SPCFG(disabled_functions_hooked); switch (data->opline->opcode) { case ZEND_INCLUDE_OR_EVAL: if (SPCFG(readonly_exec).enable) { - terminate_if_writable(ZSTR_VAL(zend_filename)); + char *fn = ZSTR_VAL(zend_filename); + if (ZSTR_LEN(zend_filename) >= strlen("file://") && memcmp(fn, "file://", strlen("file://")) == 0) { + fn += strlen("file://"); + } else if (!php_memnstr(ZSTR_VAL(zend_filename), "://", strlen("://"), ZSTR_VAL(zend_filename) + ZSTR_LEN(zend_filename))) { + // ignore stream wrappers other than file:// for now + terminate_if_writable(fn); + } } switch (data->opline->extended_value) { case ZEND_INCLUDE: -- cgit v1.3 From 490dc4e2a43a5f8256f0b00d5efd3c2a84487905 Mon Sep 17 00:00:00 2001 From: Ben Fuhrmannek Date: Tue, 19 Apr 2022 19:01:52 +0200 Subject: extended checks for readonly_exec, enabled by default introduced config options: readonly_exec.extended_checks() or xchecks() readonly_exec.no_extended_checks() or noxchecks() --- src/snuffleupagus.c | 2 ++ src/sp_config.h | 1 + src/sp_config_keywords.c | 7 ++++- src/sp_execute.c | 77 ++++++++++++++++++++++++++++++++++++++++-------- 4 files changed, 73 insertions(+), 14 deletions(-) (limited to 'src/sp_execute.c') diff --git a/src/snuffleupagus.c b/src/snuffleupagus.c index ebb7f9c..c723199 100644 --- a/src/snuffleupagus.c +++ b/src/snuffleupagus.c @@ -348,6 +348,7 @@ static void dump_config() { add_assoc_bool(&arr, "readonly_exec.enable", SPCFG(readonly_exec).enable); add_assoc_bool(&arr, "readonly_exec.sim", SPCFG(readonly_exec).simulation); ADD_ASSOC_ZSTR(&arr, SP_TOKEN_READONLY_EXEC "." SP_TOKEN_DUMP, SPCFG(readonly_exec).dump); + add_assoc_bool(&arr, "readonly_exec.extended_checks", SPCFG(readonly_exec).extended_checks); add_assoc_bool(&arr, "global_strict.enable", SPCFG(global_strict).enable); @@ -499,6 +500,7 @@ static PHP_INI_MH(OnUpdateConfiguration) { // set some defaults SPCFG(show_old_php_warning) = true; + SPCFG(readonly_exec).extended_checks = true; char *str = new_value->val; diff --git a/src/sp_config.h b/src/sp_config.h index 6d48240..e7d4e4d 100644 --- a/src/sp_config.h +++ b/src/sp_config.h @@ -35,6 +35,7 @@ typedef struct { typedef struct { bool enable; bool simulation; + bool extended_checks; zend_string *dump; zend_string *textual_representation; } sp_config_readonly_exec; diff --git a/src/sp_config_keywords.c b/src/sp_config_keywords.c index f7be731..e0e5166 100644 --- a/src/sp_config_keywords.c +++ b/src/sp_config_keywords.c @@ -96,7 +96,7 @@ SP_PARSE_FN(parse_unserialize) { } SP_PARSE_FN(parse_readonly_exec) { - bool enable = false, disable = false; + bool enable = false, disable = false, xchecks = false, no_xchecks = false; sp_config_readonly_exec *cfg = (sp_config_readonly_exec*)retval; sp_config_keyword config_keywords[] = { @@ -105,6 +105,10 @@ SP_PARSE_FN(parse_readonly_exec) { {parse_empty, SP_TOKEN_SIMULATION, &(cfg->simulation)}, {parse_empty, SP_TOKEN_SIM, &(cfg->simulation)}, {parse_str, SP_TOKEN_DUMP, &(cfg->dump)}, + {parse_empty, "extended_checks", &(xchecks)}, + {parse_empty, "xchecks", &(xchecks)}, + {parse_empty, "no_extended_checks", &(no_xchecks)}, + {parse_empty, "noxchecks", &(no_xchecks)}, {0, 0, 0}}; SP_PROCESS_CONFIG_KEYWORDS_ERR(); @@ -112,6 +116,7 @@ SP_PARSE_FN(parse_readonly_exec) { cfg->textual_representation = sp_get_textual_representation(parsed_rule); SP_SET_ENABLE_DISABLE(enable, disable, cfg->enable); + if (xchecks) { cfg->extended_checks = true; } else if (no_xchecks) { cfg->extended_checks = false; } return SP_PARSER_STOP; } diff --git a/src/sp_execute.c b/src/sp_execute.c index 9cf44e1..3a474a3 100644 --- a/src/sp_execute.c +++ b/src/sp_execute.c @@ -1,4 +1,5 @@ #include "php_snuffleupagus.h" +#include "ext/standard/php_string.h" static void (*orig_execute_ex)(zend_execute_data *execute_data) = NULL; static void (*orig_zend_execute_internal)(zend_execute_data *execute_data, @@ -12,22 +13,72 @@ static zend_result (*orig_zend_stream_open)(zend_file_handle *handle) = NULL; // FIXME handle symlink ZEND_COLD static inline void terminate_if_writable(const char *filename) { const sp_config_readonly_exec *config_ro_exec = &(SPCFG(readonly_exec)); + char *errmsg = "unknown access problem"; + + // check write access if (0 == access(filename, W_OK)) { - if (config_ro_exec->dump) { - sp_log_request(config_ro_exec->dump, config_ro_exec->textual_representation); - } - if (true == config_ro_exec->simulation) { - sp_log_simulation("readonly_exec", "Attempted execution of a writable file (%s)", filename); - } else { - sp_log_drop("readonly_exec", "Attempted execution of a writable file (%s)", filename); - } + errmsg = "Attempted execution of a writable file"; + goto violation; + } + if (errno != EACCES) { + goto err; + } + + // other checks are 'extended checks' that can be enabled/disabled via config + if (!config_ro_exec->extended_checks) { + return; + } + + // check effective uid + struct stat buf; + if (0 != stat(filename, &buf)) { + goto err; + } + if (buf.st_uid == geteuid()) { + errmsg = "Attempted execution of file owned by process"; + goto violation; + } + + // check write access on directory + char *dirname = estrndup(filename, strlen(filename)); + php_dirname(dirname, strlen(dirname)); + if (0 == access(dirname, W_OK)) { + errmsg = "Attempted execution of file in writable directory"; + efree(dirname); + goto violation; + } + if (errno != EACCES) { + efree(dirname); + goto err; + } + + // check effecite uid of directory + if (0 != stat(dirname, &buf)) { + efree(dirname); + goto err; + } + efree(dirname); + if (buf.st_uid == geteuid()) { + errmsg = "Attempted execution of file in directory owned by process"; + goto violation; + } + + // we would actually need to check all parent directories as well, but that task is left for other tools + return; + +violation: + if (config_ro_exec->dump) { + sp_log_request(config_ro_exec->dump, config_ro_exec->textual_representation); + } + if (config_ro_exec->simulation) { + sp_log_simulation("readonly_exec", "%s (%s)", errmsg, filename); } else { - if (EACCES != errno) { - // LCOV_EXCL_START - sp_log_err("Writable execution", "Error while accessing %s: %s", filename, strerror(errno)); - // LCOV_EXCL_STOP - } + sp_log_drop("readonly_exec", "%s (%s)", errmsg, filename); } + return; + +err: + sp_log_err("readonly_exec", "Error while accessing %s: %s", filename, strerror(errno)); } inline static void is_builtin_matching( -- cgit v1.3