execl(3) and its variants use a sentinel to terminate the variadic argument list, in the form of a null pointer constant of type pointer to char. POSIX mandates that NULL is a null pointer constant of type pointer to void, which is not of an equivalent type to that required by execl(3) and its variants, resulting in undefined behaviour. This commit casts all such instances of NULL to pointer to char type. For consistency, it also adds const-qualification to any such instances which had already been casted, and were not const-qualified.
131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
/*
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* Copyright (c) 2014 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* proper-sh.c
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* Forward execution to the best shell.
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*/
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#include <sys/wait.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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const char* getenv_safe(const char* name, const char* def)
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{
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const char* ret = getenv(name);
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return ret ? ret : def;
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}
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bool is_existing_shell(const char* candidate)
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{
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pid_t child_pid = fork();
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if ( child_pid < 0 )
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return false;
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if ( !child_pid )
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{
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close(0);
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close(1);
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close(2);
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open("/dev/null", O_RDONLY);
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open("/dev/null", O_WRONLY);
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open("/dev/null", O_WRONLY);
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execlp("which", "which", "--", candidate, (const char*) NULL);
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exit(127);
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}
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int status;
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waitpid(child_pid, &status, 0);
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return WIFEXITED(status) && WEXITSTATUS(status) == 0;
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}
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char* search_for_proper_shell(void)
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{
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if ( getenv("SORTIX_SH_BACKEND") )
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{
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if ( !getenv("SORTIX_SH_BACKEND")[0] )
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return NULL;
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if ( is_existing_shell(getenv("SORTIX_SH_BACKEND")) )
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return strdup(getenv("SORTIX_SH_BACKEND"));
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}
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const char* backends_dir_path =
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getenv_safe("SORTIX_SH_BACKENDS_DIR", "/etc/proper-shells");
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struct dirent** shell_entries;
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int num_shell_entries = scandir(backends_dir_path, &shell_entries, NULL, alphasort);
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if ( 0 <= num_shell_entries )
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{
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char* result = NULL;
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for ( int i = 0; i < num_shell_entries; i++ )
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{
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struct dirent* entry = shell_entries[i];
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const char* name = entry->d_name;
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if ( !strcmp(name, ".") || !strcmp(name, "..") )
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continue;
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size_t path_length = strlen(backends_dir_path) + 1 + strlen(name);
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char* path = (char*) malloc(path_length + 1);
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if ( !path )
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continue;
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stpcpy(stpcpy(stpcpy(path, backends_dir_path), "/"), name);
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FILE* fp = fopen(path, "r");
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free(path);
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if ( !fp )
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continue;
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size_t result_size = 0;
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ssize_t result_length = getline(&result, &result_size, fp);
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fclose(fp);
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if ( result_length < 0 )
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{
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free(result);
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continue;
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}
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if ( result[result_length-1] == '\n' )
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result[--result_length] = '\0';
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if ( !is_existing_shell(result) )
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{
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free(result);
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result = NULL;
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continue;
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}
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break;
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}
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for ( int i = 0; i < num_shell_entries; i++ )
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free(shell_entries[i]);
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free(shell_entries);
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if ( result )
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return result;
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}
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return NULL;
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}
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int main(int argc, char* argv[])
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{
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if ( argc == 1 && isatty(0) && isatty(1) )
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execvp("sortix-sh", argv);
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char* proper_shell = search_for_proper_shell();
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if ( proper_shell )
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execvp(proper_shell, argv);
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free(proper_shell);
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execvp("sortix-sh", argv);
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return 127;
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}
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