diff options
Diffstat (limited to 'libbb/appletlib.c')
| -rw-r--r-- | libbb/appletlib.c | 553 |
1 files changed, 549 insertions, 4 deletions
diff --git a/libbb/appletlib.c b/libbb/appletlib.c index cfa60a9..7808df5 100644 --- a/libbb/appletlib.c +++ b/libbb/appletlib.c @@ -1,11 +1,15 @@ /* vi: set sw=4 ts=4: */ /* - * Support for main() which needs to end up in libbusybox, not busybox, - * if one builds libbusybox. + * Utility routines. * - * Copyright (C) 2007 Denys Vlasenko <vda.linux@googlemail.com> + * Copyright (C) tons of folks. Tracking down who wrote what + * isn't something I'm going to worry about... If you wrote something + * here, please feel free to acknowledge your work. * - * Licensed under GPLv2, see file License in this tarball for details. + * Based in part on code from sash, Copyright (c) 1999 by David I. Bell + * Permission has been granted to redistribute this code under the GPL. + * + * Licensed under GPLv2 or later, see file License in this tarball for details. */ #include <assert.h> @@ -140,3 +144,544 @@ void bbox_prepare_main(char **argv) bb_show_usage(); #endif } + +/* The code below can well be in applets/applets.c, as it is used only + * for busybox binary, not "individual" binaries. + * However, keeping it here and linking it into libbusybox.so + * (together with remaining tiny applets/applets.o) + * makes it possible to avoid --whole-archive at link time. + * This makes (shared busybox) + libbusybox smaller. + * (--gc-sections would be even better....) + */ + +const char *applet_name; +#if !BB_MMU +bool re_execed; +#endif + +USE_FEATURE_SUID(static uid_t ruid;) /* real uid */ + +#if ENABLE_FEATURE_SUID_CONFIG + +/* applets[] is const, so we have to define this "override" structure */ +static struct BB_suid_config { + const struct bb_applet *m_applet; + uid_t m_uid; + gid_t m_gid; + mode_t m_mode; + struct BB_suid_config *m_next; +} *suid_config; + +static bool suid_cfg_readable; + +/* check if u is member of group g */ +static int ingroup(uid_t u, gid_t g) +{ + struct group *grp = getgrgid(g); + + if (grp) { + char **mem; + + for (mem = grp->gr_mem; *mem; mem++) { + struct passwd *pwd = getpwnam(*mem); + + if (pwd && (pwd->pw_uid == u)) + return 1; + } + } + return 0; +} + +/* This should probably be a libbb routine. In that case, + * I'd probably rename it to something like bb_trimmed_slice. + */ +static char *get_trimmed_slice(char *s, char *e) +{ + /* First, consider the value at e to be nul and back up until we + * reach a non-space char. Set the char after that (possibly at + * the original e) to nul. */ + while (e-- > s) { + if (!isspace(*e)) { + break; + } + } + e[1] = '\0'; + + /* Next, advance past all leading space and return a ptr to the + * first non-space char; possibly the terminating nul. */ + return skip_whitespace(s); +} + +/* Don't depend on the tools to combine strings. */ +static const char config_file[] ALIGN1 = "/etc/busybox.conf"; + +/* We don't supply a value for the nul, so an index adjustment is + * necessary below. Also, we use unsigned short here to save some + * space even though these are really mode_t values. */ +static const unsigned short mode_mask[] ALIGN2 = { + /* SST sst xxx --- */ + S_ISUID, S_ISUID|S_IXUSR, S_IXUSR, 0, /* user */ + S_ISGID, S_ISGID|S_IXGRP, S_IXGRP, 0, /* group */ + 0, S_IXOTH, S_IXOTH, 0 /* other */ +}; + +#define parse_error(x) do { errmsg = x; goto pe_label; } while (0) + +static void parse_config_file(void) +{ + struct BB_suid_config *sct_head; + struct BB_suid_config *sct; + const struct bb_applet *applet; + FILE *f; + const char *errmsg; + char *s; + char *e; + int i; + unsigned lc; + smallint section; + char buffer[256]; + struct stat st; + + assert(!suid_config); /* Should be set to NULL by bss init. */ + + ruid = getuid(); + if (ruid == 0) /* run by root - don't need to even read config file */ + return; + + if ((stat(config_file, &st) != 0) /* No config file? */ + || !S_ISREG(st.st_mode) /* Not a regular file? */ + || (st.st_uid != 0) /* Not owned by root? */ + || (st.st_mode & (S_IWGRP | S_IWOTH)) /* Writable by non-root? */ + || !(f = fopen(config_file, "r")) /* Cannot open? */ + ) { + return; + } + + suid_cfg_readable = 1; + sct_head = NULL; + section = lc = 0; + + while (1) { + s = buffer; + + if (!fgets(s, sizeof(buffer), f)) { /* Are we done? */ + if (ferror(f)) { /* Make sure it wasn't a read error. */ + parse_error("reading"); + } + fclose(f); + suid_config = sct_head; /* Success, so set the pointer. */ + return; + } + + lc++; /* Got a (partial) line. */ + + /* If a line is too long for our buffer, we consider it an error. + * The following test does mistreat one corner case though. + * If the final line of the file does not end with a newline and + * yet exactly fills the buffer, it will be treated as too long + * even though there isn't really a problem. But it isn't really + * worth adding code to deal with such an unlikely situation, and + * we do err on the side of caution. Besides, the line would be + * too long if it did end with a newline. */ + if (!strchr(s, '\n') && !feof(f)) { + parse_error("line too long"); + } + + /* Trim leading and trailing whitespace, ignoring comments, and + * check if the resulting string is empty. */ + s = get_trimmed_slice(s, strchrnul(s, '#')); + if (!*s) { + continue; + } + + /* Check for a section header. */ + + if (*s == '[') { + /* Unlike the old code, we ignore leading and trailing + * whitespace for the section name. We also require that + * there are no stray characters after the closing bracket. */ + e = strchr(s, ']'); + if (!e /* Missing right bracket? */ + || e[1] /* Trailing characters? */ + || !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */ + ) { + parse_error("section header"); + } + /* Right now we only have one section so just check it. + * If more sections are added in the future, please don't + * resort to cascading ifs with multiple strcasecmp calls. + * That kind of bloated code is all too common. A loop + * and a string table would be a better choice unless the + * number of sections is very small. */ + if (strcasecmp(s, "SUID") == 0) { + section = 1; + continue; + } + section = -1; /* Unknown section so set to skip. */ + continue; + } + + /* Process sections. */ + + if (section == 1) { /* SUID */ + /* Since we trimmed leading and trailing space above, we're + * now looking for strings of the form + * <key>[::space::]*=[::space::]*<value> + * where both key and value could contain inner whitespace. */ + + /* First get the key (an applet name in our case). */ + e = strchr(s, '='); + if (e) { + s = get_trimmed_slice(s, e); + } + if (!e || !*s) { /* Missing '=' or empty key. */ + parse_error("keyword"); + } + + /* Ok, we have an applet name. Process the rhs if this + * applet is currently built in and ignore it otherwise. + * Note: this can hide config file bugs which only pop + * up when the busybox configuration is changed. */ + applet = find_applet_by_name(s); + if (applet) { + /* Note: We currently don't check for duplicates! + * The last config line for each applet will be the + * one used since we insert at the head of the list. + * I suppose this could be considered a feature. */ + sct = xmalloc(sizeof(struct BB_suid_config)); + sct->m_applet = applet; + sct->m_mode = 0; + sct->m_next = sct_head; + sct_head = sct; + + /* Get the specified mode. */ + + e = skip_whitespace(e+1); + + for (i = 0; i < 3; i++) { + /* There are 4 chars + 1 nul for each of user/group/other. */ + static const char mode_chars[] ALIGN1 = "Ssx-\0" "Ssx-\0" "Ttx-"; + + const char *q; + q = strchrnul(mode_chars + 5*i, *e++); + if (!*q) { + parse_error("mode"); + } + /* Adjust by -i to account for nul. */ + sct->m_mode |= mode_mask[(q - mode_chars) - i]; + } + + /* Now get the the user/group info. */ + + s = skip_whitespace(e); + + /* Note: we require whitespace between the mode and the + * user/group info. */ + if ((s == e) || !(e = strchr(s, '.'))) { + parse_error("<uid>.<gid>"); + } + *e++ = '\0'; + + /* We can't use get_ug_id here since it would exit() + * if a uid or gid was not found. Oh well... */ + sct->m_uid = bb_strtoul(s, NULL, 10); + if (errno) { + struct passwd *pwd = getpwnam(s); + if (!pwd) { + parse_error("user"); + } + sct->m_uid = pwd->pw_uid; + } + + sct->m_gid = bb_strtoul(e, NULL, 10); + if (errno) { + struct group *grp; + grp = getgrnam(e); + if (!grp) { + parse_error("group"); + } + sct->m_gid = grp->gr_gid; + } + } + continue; + } + + /* Unknown sections are ignored. */ + + /* Encountering configuration lines prior to seeing a + * section header is treated as an error. This is how + * the old code worked, but it may not be desirable. + * We may want to simply ignore such lines in case they + * are used in some future version of busybox. */ + if (!section) { + parse_error("keyword outside section"); + } + + } /* while (1) */ + + pe_label: + fprintf(stderr, "Parse error in %s, line %d: %s\n", + config_file, lc, errmsg); + + fclose(f); + /* Release any allocated memory before returning. */ + while (sct_head) { + sct = sct_head->m_next; + free(sct_head); + sct_head = sct; + } +} +#else +static inline void parse_config_file(void) +{ + USE_FEATURE_SUID(ruid = getuid();) +} +#endif /* FEATURE_SUID_CONFIG */ + + +#if ENABLE_FEATURE_SUID +static void check_suid(const struct bb_applet *applet) +{ + gid_t rgid; /* real gid */ + + if (ruid == 0) /* set by parse_config_file() */ + return; /* run by root - no need to check more */ + rgid = getgid(); + +#if ENABLE_FEATURE_SUID_CONFIG + if (suid_cfg_readable) { + uid_t uid; + struct BB_suid_config *sct; + mode_t m; + + for (sct = suid_config; sct; sct = sct->m_next) { + if (sct->m_applet == applet) + goto found; + } + /* default: drop all privileges */ + xsetgid(rgid); + xsetuid(ruid); + return; + found: + m = sct->m_mode; + if (sct->m_uid == ruid) + /* same uid */ + m >>= 6; + else if ((sct->m_gid == rgid) || ingroup(ruid, sct->m_gid)) + /* same group / in group */ + m >>= 3; + + if (!(m & S_IXOTH)) /* is x bit not set ? */ + bb_error_msg_and_die("you have no permission to run this applet!"); + + /* _both_ sgid and group_exec have to be set for setegid */ + if ((sct->m_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) + rgid = sct->m_gid; + /* else (no setegid) we will set egid = rgid */ + + /* We set effective AND saved ids. If saved-id is not set + * like we do below, seteiud(0) can still later succeed! */ + if (setresgid(-1, rgid, rgid)) + bb_perror_msg_and_die("setresgid"); + + /* do we have to set effective uid? */ + uid = ruid; + if (sct->m_mode & S_ISUID) + uid = sct->m_uid; + /* else (no seteuid) we will set euid = ruid */ + + if (setresuid(-1, uid, uid)) + bb_perror_msg_and_die("setresuid"); + return; + } +#if !ENABLE_FEATURE_SUID_CONFIG_QUIET + { + static bool onetime = 0; + + if (!onetime) { + onetime = 1; + fprintf(stderr, "Using fallback suid method\n"); + } + } +#endif +#endif + + if (applet->need_suid == _BB_SUID_ALWAYS) { + /* Real uid is not 0. If euid isn't 0 too, suid bit + * is most probably not set on our executable */ + if (geteuid()) + bb_error_msg_and_die("applet requires root privileges!"); + } else if (applet->need_suid == _BB_SUID_NEVER) { + xsetgid(rgid); /* drop all privileges */ + xsetuid(ruid); + } +} +#else +#define check_suid(x) ((void)0) +#endif /* FEATURE_SUID */ + + +#if ENABLE_FEATURE_INSTALLER +/* create (sym)links for each applet */ +static void install_links(const char *busybox, int use_symbolic_links) +{ + /* directory table + * this should be consistent w/ the enum, + * busybox.h::bb_install_loc_t, or else... */ + static const char usr_bin [] ALIGN1 = "/usr/bin"; + static const char usr_sbin[] ALIGN1 = "/usr/sbin"; + static const char *const install_dir[] = { + &usr_bin [8], /* "", equivalent to "/" for concat_path_file() */ + &usr_bin [4], /* "/bin" */ + &usr_sbin[4], /* "/sbin" */ + usr_bin, + usr_sbin + }; + + int (*lf)(const char *, const char *) = link; + char *fpc; + int i; + int rc; + + if (use_symbolic_links) + lf = symlink; + + for (i = 0; applets[i].name != NULL; i++) { + fpc = concat_path_file( + install_dir[applets[i].install_loc], + applets[i].name); + rc = lf(busybox, fpc); + if (rc != 0 && errno != EEXIST) { + bb_simple_perror_msg(fpc); + } + free(fpc); + } +} +#else +#define install_links(x,y) ((void)0) +#endif /* FEATURE_INSTALLER */ + +/* If we were called as "busybox..." */ +static int busybox_main(char **argv) +{ + if (!argv[1]) { + /* Called without arguments */ + const struct bb_applet *a; + int col, output_width; + help: + output_width = 80; + if (ENABLE_FEATURE_AUTOWIDTH) { + /* Obtain the terminal width */ + get_terminal_width_height(0, &output_width, NULL); + } + /* leading tab and room to wrap */ + output_width -= sizeof("start-stop-daemon, ") + 8; + + printf("%s multi-call binary\n", bb_banner); /* reuse const string... */ + printf("Copyright (C) 1998-2006 Erik Andersen, Rob Landley, and others.\n" + "Licensed under GPLv2. See source distribution for full notice.\n" + "\n" + "Usage: busybox [function] [arguments]...\n" + " or: [function] [arguments]...\n" + "\n" + "\tBusyBox is a multi-call binary that combines many common Unix\n" + "\tutilities into a single executable. Most people will create a\n" + "\tlink to busybox for each function they wish to use and BusyBox\n" + "\twill act like whatever it was invoked as!\n" + "\nCurrently defined functions:\n"); + col = 0; + a = applets; + while (a->name) { + if (col > output_width) { + puts(","); + col = 0; + } + col += printf("%s%s", (col ? ", " : "\t"), a->name); + a++; + } + puts("\n"); + return 0; + } + + if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) { + const char *busybox; + busybox = xmalloc_readlink(bb_busybox_exec_path); + if (!busybox) + busybox = bb_busybox_exec_path; + /* -s makes symlinks */ + install_links(busybox, argv[2] && strcmp(argv[2], "-s") == 0); + return 0; + } + + if (strcmp(argv[1], "--help") == 0) { + /* "busybox --help [<applet>]" */ + if (!argv[2]) + goto help; + /* convert to "<applet> --help" */ + argv[0] = argv[2]; + argv[2] = NULL; + } else { + /* "busybox <applet> arg1 arg2 ..." */ + argv++; + } + /* We support "busybox /a/path/to/applet args..." too. Allows for + * "#!/bin/busybox"-style wrappers */ + applet_name = bb_get_last_path_component_nostrip(argv[0]); + run_applet_and_exit(applet_name, argv); + bb_error_msg_and_die("applet not found"); +} + +void run_appletstruct_and_exit(const struct bb_applet *applet, char **argv) +{ + int argc = 1; + + while (argv[argc]) + argc++; + + /* Reinit some shared global data */ + optind = 1; + xfunc_error_retval = EXIT_FAILURE; + + applet_name = applet->name; + if (argc == 2 && !strcmp(argv[1], "--help")) + bb_show_usage(); + if (ENABLE_FEATURE_SUID) + check_suid(applet); + exit(applet->main(argc, argv)); +} + +void run_applet_and_exit(const char *name, char **argv) +{ + const struct bb_applet *applet = find_applet_by_name(name); + if (applet) + run_appletstruct_and_exit(applet, argv); + if (!strncmp(name, "busybox", 7)) + exit(busybox_main(argv)); +} + + +#if ENABLE_BUILD_LIBBUSYBOX +int libbusybox_main(int argc, char **argv) +#else +int main(int argc, char **argv) +#endif +{ + bbox_prepare_main(argv); + +#if !BB_MMU + /* NOMMU re-exec trick sets high-order bit in first byte of name */ + if (argv[0][0] & 0x80) { + re_execed = 1; + argv[0][0] &= 0x7f; + } +#endif + applet_name = argv[0]; + if (applet_name[0] == '-') + applet_name++; + applet_name = bb_basename(applet_name); + + parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */ + + run_applet_and_exit(applet_name, argv); + bb_error_msg_and_die("applet not found"); +} |