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Diffstat (limited to 'src/linker/linker_environ.c')
| -rw-r--r-- | src/linker/linker_environ.c | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/src/linker/linker_environ.c b/src/linker/linker_environ.c new file mode 100644 index 0000000..ca8b1d9 --- /dev/null +++ b/src/linker/linker_environ.c @@ -0,0 +1,204 @@ +/* + * 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** apkenv__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 +apkenv__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* +apkenv_linker_env_init(unsigned* vecs) +{ + /* Store environment pointer - can't be NULL */ + apkenv__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 = apkenv__envp; + char** writep = apkenv__envp; + for ( ; readp[0] != NULL; readp++ ) { + if (!apkenv__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* +apkenv_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* +apkenv_linker_env_get(const char* name) +{ + char** readp = apkenv__envp; + + if (name == NULL || name[0] == '\0') + return NULL; + + for ( ; readp[0] != NULL; readp++ ) { + char* val = apkenv_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 +apkenv_linker_env_unset(const char* name) +{ + char** readp = apkenv__envp; + char** writep = readp; + + if (name == NULL || name[0] == '\0') + return; + + for ( ; readp[0] != NULL; readp++ ) { + if (apkenv_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 +apkenv_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) { + apkenv_linker_env_unset(*cp); + cp++; + } +} |