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| -rw-r--r-- | libbb/safe_gethostname.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/libbb/safe_gethostname.c b/libbb/safe_gethostname.c new file mode 100644 index 0000000..1290f4c --- /dev/null +++ b/libbb/safe_gethostname.c @@ -0,0 +1,53 @@ +/* vi: set sw=4 ts=4: */ +/* + * Safe gethostname implementation for busybox + * + * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it> + * + * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. + */ + +/* + * SUSv2 guarantees that "Host names are limited to 255 bytes" + * POSIX.1-2001 guarantees that "Host names (not including the terminating + * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box). + * + * RFC1123 says: + * + * The syntax of a legal Internet host name was specified in RFC-952 + * [DNS:4]. One aspect of host name syntax is hereby changed: the + * restriction on the first character is relaxed to allow either a + * letter or a digit. Host software MUST support this more liberal + * syntax. + * + * Host software MUST handle host names of up to 63 characters and + * SHOULD handle host names of up to 255 characters. + */ + +#include "libbb.h" +#include <sys/utsname.h> + +/* + * On success return the current malloced and NUL terminated hostname. + * On error return malloced and NUL terminated string "?". + * This is an illegal first character for a hostname. + * The returned malloced string must be freed by the caller. + */ +char *safe_gethostname(void) +{ + struct utsname uts; + + /* The length of the arrays in a struct utsname is unspecified; + * the fields are terminated by a null byte. + * Note that there is no standard that says that the hostname + * set by sethostname(2) is the same string as the nodename field of the + * struct returned by uname (indeed, some systems allow a 256-byte host- + * name and an 8-byte nodename), but this is true on Linux. The same holds + * for setdomainname(2) and the domainname field. + */ + + /* Uname can fail only if you pass a bad pointer to it. */ + uname(&uts); + + return xstrndup(!*(uts.nodename) ? "?" : uts.nodename, sizeof(uts.nodename)); +} |