| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| #include "linker_environ.h" |
| #include <stddef.h> |
| |
| static char** _envp; |
| |
| /* Returns 1 if 'str' points to a valid environment variable definition. |
| * For now, we check that: |
| * - It is smaller than MAX_ENV_LEN (to detect non-zero terminated strings) |
| * - It contains at least one equal sign that is not the first character |
| */ |
| static int |
| _is_valid_definition(const char* str) |
| { |
| int pos = 0; |
| int first_equal_pos = -1; |
| |
| /* According to its sources, the kernel uses 32*PAGE_SIZE by default |
| * as the maximum size for an env. variable definition. |
| */ |
| const int MAX_ENV_LEN = 32*4096; |
| |
| if (str == NULL) |
| return 0; |
| |
| /* Parse the string, looking for the first '=' there, and its size */ |
| do { |
| if (str[pos] == '\0') |
| break; |
| if (str[pos] == '=' && first_equal_pos < 0) |
| first_equal_pos = pos; |
| pos++; |
| } while (pos < MAX_ENV_LEN); |
| |
| if (pos >= MAX_ENV_LEN) /* Too large */ |
| return 0; |
| |
| if (first_equal_pos < 1) /* No equal sign, or it is the first character */ |
| return 0; |
| |
| return 1; |
| } |
| |
| unsigned* |
| linker_env_init(unsigned* vecs) |
| { |
| /* Store environment pointer - can't be NULL */ |
| _envp = (char**) vecs; |
| |
| /* Skip over all definitions */ |
| while (vecs[0] != 0) |
| vecs++; |
| /* The end of the environment block is marked by two NULL pointers */ |
| vecs++; |
| |
| /* As a sanity check, we're going to remove all invalid variable |
| * definitions from the environment array. |
| */ |
| { |
| char** readp = _envp; |
| char** writep = _envp; |
| for ( ; readp[0] != NULL; readp++ ) { |
| if (!_is_valid_definition(readp[0])) |
| continue; |
| writep[0] = readp[0]; |
| writep++; |
| } |
| writep[0] = NULL; |
| } |
| |
| /* Return the address of the aux vectors table */ |
| return vecs; |
| } |
| |
| /* Check if the environment variable definition at 'envstr' |
| * starts with '<name>=', and if so return the address of the |
| * first character after the equal sign. Otherwise return NULL. |
| */ |
| static char* |
| env_match(char* envstr, const char* name) |
| { |
| size_t cnt = 0; |
| |
| while (envstr[cnt] == name[cnt] && name[cnt] != '\0') |
| cnt++; |
| |
| if (name[cnt] != '\0' && envstr[cnt] == '=') |
| return envstr + cnt + 1; |
| |
| return NULL; |
| } |
| |
| #define MAX_ENV_LEN (16*4096) |
| |
| const char* |
| linker_env_get(const char* name) |
| { |
| char** readp = _envp; |
| |
| if (name == NULL || name[0] == '\0') |
| return NULL; |
| |
| for ( ; readp[0] != NULL; readp++ ) { |
| char* val = env_match(readp[0], name); |
| if (val != NULL) { |
| /* Return NULL for empty strings, or if it is too large */ |
| if (val[0] == '\0') |
| val = NULL; |
| return val; |
| } |
| } |
| return NULL; |
| } |
| |
| |
| void |
| linker_env_unset(const char* name) |
| { |
| char** readp = _envp; |
| char** writep = readp; |
| |
| if (name == NULL || name[0] == '\0') |
| return; |
| |
| for ( ; readp[0] != NULL; readp++ ) { |
| if (env_match(readp[0], name)) |
| continue; |
| writep[0] = readp[0]; |
| writep++; |
| } |
| /* end list with a NULL */ |
| writep[0] = NULL; |
| } |
| |
| |
| |
| /* Remove unsafe environment variables. This should be used when |
| * running setuid programs. */ |
| void |
| linker_env_secure(void) |
| { |
| /* The same list than GLibc at this point */ |
| static const char* const unsec_vars[] = { |
| "GCONV_PATH", |
| "GETCONF_DIR", |
| "HOSTALIASES", |
| "LD_AUDIT", |
| "LD_DEBUG", |
| "LD_DEBUG_OUTPUT", |
| "LD_DYNAMIC_WEAK", |
| "LD_LIBRARY_PATH", |
| "LD_ORIGIN_PATH", |
| "LD_PRELOAD", |
| "LD_PROFILE", |
| "LD_SHOW_AUXV", |
| "LD_USE_LOAD_BIAS", |
| "LOCALDOMAIN", |
| "LOCPATH", |
| "MALLOC_TRACE", |
| "MALLOC_CHECK_", |
| "NIS_PATH", |
| "NLSPATH", |
| "RESOLV_HOST_CONF", |
| "RES_OPTIONS", |
| "TMPDIR", |
| "TZDIR", |
| "LD_AOUT_LIBRARY_PATH", |
| "LD_AOUT_PRELOAD", |
| }; |
| |
| const char* const* cp = unsec_vars; |
| const char* const* endp = cp + sizeof(unsec_vars)/sizeof(unsec_vars[0]); |
| |
| while (cp < endp) { |
| linker_env_unset(*cp); |
| cp++; |
| } |
| } |