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, (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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