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([2804:1b3:a7c2:94e:ee04:b0d3:203c:7e3]) by smtp.gmail.com with ESMTPSA id a4-20020a170902ee8400b001c9d011581dsm9736021pld.164.2023.11.22.04.36.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Nov 2023 04:36:15 -0800 (PST) From: Adhemerval Zanella To: libc-alpha@sourceware.org, siddhesh@sourceware.org Subject: [PATCH v4 4/4] elf: Refactor process_envvars Date: Wed, 22 Nov 2023 09:36:01 -0300 Message-Id: <20231122123601.603315-5-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231122123601.603315-1-adhemerval.zanella@linaro.org> References: <20231122123601.603315-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org It splits between process_envvars_secure and process_envvars_default, with the former used to process arguments for __libc_enable_secure. It does not have any semantic change, just simplify the code so there is no need to handle __libc_enable_secure on each len switch. Checked on x86_64-linux-gnu and aarch64-linux-gnu. Reviewed-by: Siddhesh Poyarekar --- elf/rtld.c | 132 ++++++++++++++++++++++++++++++++++------------------- 1 file changed, 84 insertions(+), 48 deletions(-) diff --git a/elf/rtld.c b/elf/rtld.c index cfba30eba0..95dcd32185 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -2527,7 +2527,67 @@ a filename can be specified using the LD_DEBUG_OUTPUT environment variable.\n"); } static void -process_envvars (struct dl_main_state *state) +process_envvars_secure (struct dl_main_state *state) +{ + char **runp = _environ; + char *envline; + + while ((envline = _dl_next_ld_env_entry (&runp)) != NULL) + { + size_t len = 0; + + while (envline[len] != '\0' && envline[len] != '=') + ++len; + + if (envline[len] != '=') + /* This is a "LD_" variable at the end of the string without + a '=' character. Ignore it since otherwise we will access + invalid memory below. */ + continue; + + switch (len) + { + case 5: + /* For __libc_enable_secure mode, audit pathnames containing slashes + are ignored. Also, shared audit objects are only loaded only from + the standard search directories and only if they have set-user-ID + mode bit enabled. */ + if (memcmp (envline, "AUDIT", 5) == 0) + audit_list_add_string (&state->audit_list, &envline[6]); + break; + + case 7: + /* For __libc_enable_secure mode, preload pathnames containing slashes + are ignored. Also, shared objects are only preloaded from the + standard search directories and only if they have set-user-ID mode + bit enabled. */ + if (memcmp (envline, "PRELOAD", 7) == 0) + state->preloadlist = &envline[8]; + break; + } + } + + /* Extra security for SUID binaries. Remove all dangerous environment + variables. */ + const char *nextp = UNSECURE_ENVVARS; + do + { + unsetenv (nextp); + nextp = strchr (nextp, '\0') + 1; + } + while (*nextp != '\0'); + + if (GLRO(dl_debug_mask) != 0 + || GLRO(dl_verbose) != 0 + || GLRO(dl_lazy) != 1 + || GLRO(dl_bind_not) != 0 + || state->mode != rtld_mode_normal + || state->version_info) + _exit (5); +} + +static void +process_envvars_default (struct dl_main_state *state) { char **runp = _environ; char *envline; @@ -2550,15 +2610,13 @@ process_envvars (struct dl_main_state *state) { case 4: /* Warning level, verbose or not. */ - if (!__libc_enable_secure - && memcmp (envline, "WARN", 4) == 0) + if (memcmp (envline, "WARN", 4) == 0) GLRO(dl_verbose) = envline[5] != '\0'; break; case 5: /* Debugging of the dynamic linker? */ - if (!__libc_enable_secure - && memcmp (envline, "DEBUG", 5) == 0) + if (memcmp (envline, "DEBUG", 5) == 0) { process_dl_debug (state, &envline[6]); break; @@ -2573,8 +2631,7 @@ process_envvars (struct dl_main_state *state) case 7: /* Print information about versions. */ - if (!__libc_enable_secure - && memcmp (envline, "VERBOSE", 7) == 0) + if (memcmp (envline, "VERBOSE", 7) == 0) { state->version_info = envline[8] != '\0'; break; @@ -2591,43 +2648,37 @@ process_envvars (struct dl_main_state *state) } /* Which shared object shall be profiled. */ - if (!__libc_enable_secure - && memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0') + if (memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0') GLRO(dl_profile) = &envline[8]; break; case 8: /* Do we bind early? */ - if (!__libc_enable_secure - && memcmp (envline, "BIND_NOW", 8) == 0) + if (memcmp (envline, "BIND_NOW", 8) == 0) { GLRO(dl_lazy) = envline[9] == '\0'; break; } - if (! __libc_enable_secure - && memcmp (envline, "BIND_NOT", 8) == 0) + if (memcmp (envline, "BIND_NOT", 8) == 0) GLRO(dl_bind_not) = envline[9] != '\0'; break; case 9: /* Test whether we want to see the content of the auxiliary array passed up from the kernel. */ - if (!__libc_enable_secure - && memcmp (envline, "SHOW_AUXV", 9) == 0) + if (memcmp (envline, "SHOW_AUXV", 9) == 0) _dl_show_auxv (); break; case 11: /* Path where the binary is found. */ - if (!__libc_enable_secure - && memcmp (envline, "ORIGIN_PATH", 11) == 0) + if (memcmp (envline, "ORIGIN_PATH", 11) == 0) GLRO(dl_origin_path) = &envline[12]; break; case 12: /* The library search path. */ - if (!__libc_enable_secure - && memcmp (envline, "LIBRARY_PATH", 12) == 0) + if (memcmp (envline, "LIBRARY_PATH", 12) == 0) { state->library_path = &envline[13]; state->library_path_source = "LD_LIBRARY_PATH"; @@ -2635,30 +2686,26 @@ process_envvars (struct dl_main_state *state) } /* Where to place the profiling data file. */ - if (!__libc_enable_secure - && memcmp (envline, "DEBUG_OUTPUT", 12) == 0) + if (memcmp (envline, "DEBUG_OUTPUT", 12) == 0) { debug_output = &envline[13]; break; } - if (!__libc_enable_secure - && memcmp (envline, "DYNAMIC_WEAK", 12) == 0) + if (memcmp (envline, "DYNAMIC_WEAK", 12) == 0) GLRO(dl_dynamic_weak) = 1; break; case 14: /* Where to place the profiling data file. */ - if (!__libc_enable_secure - && memcmp (envline, "PROFILE_OUTPUT", 14) == 0 + if (memcmp (envline, "PROFILE_OUTPUT", 14) == 0 && envline[15] != '\0') GLRO(dl_profile_output) = &envline[15]; break; case 20: /* The mode of the dynamic linker can be set. */ - if (!__libc_enable_secure - && memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0) + if (memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0) { state->mode = rtld_mode_trace; state->mode_trace_program @@ -2668,30 +2715,10 @@ process_envvars (struct dl_main_state *state) } } - /* Extra security for SUID binaries. Remove all dangerous environment - variables. */ - if (__glibc_unlikely (__libc_enable_secure)) - { - const char *nextp = UNSECURE_ENVVARS; - do - { - unsetenv (nextp); - nextp = strchr (nextp, '\0') + 1; - } - while (*nextp != '\0'); - - if (GLRO(dl_debug_mask) != 0 - || GLRO(dl_verbose) != 0 - || GLRO(dl_lazy) != 1 - || GLRO(dl_bind_not) != 0 - || state->mode != rtld_mode_normal - || state->version_info) - _exit (5); - } /* If we have to run the dynamic linker in debugging mode and the LD_DEBUG_OUTPUT environment variable is given, we write the debug messages to this file. */ - else if (GLRO(dl_debug_mask) != 0 && debug_output != NULL) + if (GLRO(dl_debug_mask) != 0 && debug_output != NULL) { const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NOFOLLOW; size_t name_len = strlen (debug_output); @@ -2710,6 +2737,15 @@ process_envvars (struct dl_main_state *state) } } +static void +process_envvars (struct dl_main_state *state) +{ + if (__glibc_unlikely (__libc_enable_secure)) + process_envvars_secure (state); + else + process_envvars_default (state); +} + #if HP_TIMING_INLINE static void print_statistics_item (const char *title, hp_timing_t time,