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agetty: improve login(1) argv[] 

* fix regression: missing username should not be reported (EPERM) if
  -n/--skip-login is given and username is NULL.

* don't compose login options *string* if we can use argv *array* (the
  string is necessary only for --login-options).

* don't overwrite --login-options by --autologin

  The old code silently ignores login-options and "login -f <username>"
  is always used.

  The new code uses:
    a)	"login -f <username>"    by default
    b)	"login <login-options>"  for --login-options + --autologin

  where for b) the username from "--autologin <username>" is used to
  replace \u magic string in <login-options>.

* the \u could be used more than once in one login argv string, for
  example: agetty --login-options "-o user=\\u,name=\\u --foo"

* the space in --login-options is correctly ignored, for example
  agetty --login-options " hello world ".

Reviewed-by: Voelker, Bernhard <bernhard.voelker@siemens-enterprise.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2011-08-04 18:37:25 +02:00
parent baecaf21ce
commit 9aeb66dc6b
2 changed files with 121 additions and 72 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
term-utils/agetty.8
View File

@ -87,9 +87,11 @@ whatever init(8) may have set, and is inherited by login and the shell.
Assume that the tty is 8-bit clean, hence disable parity detection.
.TP
\-a, \-\-autologin \fIusername\fP
Log the specified user automatically in without asking for a login
name and password. Check the \-f option from
\fB/bin/login\fP for this.
Log the specified user automatically in without asking for a login name and
password. The \-f \fIusername\fP option is added to the \fB/bin/login\fP
command line by default. The \-\-login-options option changes this default
behaviour and then only \\u is replaced by the \fIusername\fP and no other
option is added to the login command line.
.TP
\-c, \-\-noreset
Don't reset terminal cflags (control modes). See \fItermios(3)\fP for more
@ -160,9 +162,10 @@ is run as root.
.TP
\-o, \-\-login\-options \fI"login_options"\fP
Options that are passed to the login program. \\u is replaced
by the login name. Defaults to "-- \\u", which is suitable for
\fB/bin/login\fP. Please read the SECURITY NOTICE below if
you want to use this.
by the login name. The default \fB/bin/login\fP command line
is "/bin/login -- <username>".
Please read the SECURITY NOTICE below if you want to use this.
.TP
\-p, \-\-login\-pause
Wait for any key before dropping to the login prompt. Can be combined

178
term-utils/agetty.c
View File

@ -100,7 +100,7 @@
/* Login prompt. */
#define LOGIN "login: "
#define ARRAY_SIZE_MAX 16 /* Numbers of args for login beside "-- \\u" */
#define LOGIN_ARGV_MAX 16 /* Numbers of args for login */
/* Some shorthands for control characters. */
#define CTL(x) (x ^ 0100) /* Assumes ASCII dialect */
@ -262,9 +262,8 @@ static void log_err(const char *, ...) __attribute__((__noreturn__))
static void log_warn (const char *, ...)
__attribute__((__format__(printf, 1, 2)));
static ssize_t append(char *dest, size_t len, const char *sep, const char *src);
static void checkname (const char* nm);
static void replacename (char** arr, const char* nm);
static void mkarray (char** arr, char* str);
static void check_username (const char* nm);
static void login_options_to_argv(char *argv[], int *argc, char *str, char *username);
/* Fake hostname for ut_host specified on command line. */
static char *fakehost;
@ -278,19 +277,18 @@ FILE *dbf;
int main(int argc, char **argv)
{
char *logname = NULL; /* login name, given to /bin/login */
char logcmd[NAME_MAX+1];
char *logarr[ARRAY_SIZE_MAX + 2]; /* arguments plus "-- \\u" */
char *username = NULL; /* login name, given to /bin/login */
struct chardata chardata; /* will be set by get_logname() */
struct termios termios; /* terminal mode bits */
static struct options options = {
.flags = F_ISSUE, /* show /etc/issue (SYSV_STYLE) */
.login = _PATH_LOGIN, /* default login program */
.logopt = "-- \\u", /* escape for user name */
.tty = "tty1", /* default tty line */
.term = DEFAULT_VCTERM, /* terminal type */
.issue = ISSUE /* default issue file */
};
char *login_argv[LOGIN_ARGV_MAX + 1];
int login_argc = 0;
struct sigaction sa, sa_hup, sa_quit, sa_int;
sigset_t set;
@ -315,6 +313,8 @@ int main(int argc, char **argv)
/* Parse command-line arguments. */
parse_args(argc, argv, &options);
login_argv[login_argc++] = options.login; /* set login program name */
/* Update the utmp file. */
#ifdef SYSV_STYLE
update_utmp(&options);
@ -379,16 +379,15 @@ int main(int argc, char **argv)
chardata = init_chardata;
if ((options.flags & F_NOPROMPT) == 0) {
if (options.autolog) {
/* Do the auto login */
/* Do the auto login. */
debug("doing auto login\n");
do_prompt(&options, &termios);
printf("%s%s (automatic login)\n", LOGIN, options.autolog);
logname = options.autolog;
options.logopt = "-f \\u";
username = options.autolog;
} else {
/* Read the login name. */
debug("reading login name\n");
while ((logname =
while ((username =
get_logname(&options, &termios, &chardata)) == 0)
if ((options.flags & F_VCONSOLE) == 0)
next_speed(&options, &termios);
@ -410,13 +409,25 @@ int main(int argc, char **argv)
sigaction(SIGQUIT, &sa_quit, NULL);
sigaction(SIGINT, &sa_int, NULL);
*logcmd = '\0';
append(logcmd, sizeof(logcmd), NULL, options.login);
append(logcmd, sizeof(logcmd), " ", options.logopt);
if (username)
check_username(username);
checkname(logname);
mkarray(logarr, logcmd);
replacename(logarr, logname);
if (options.logopt) {
/*
* The --login-options completely overwrites the default
* way how agetty composes login(1) command line.
*/
login_options_to_argv(login_argv, &login_argc,
options.logopt, username);
} else if (username) {
if (options.autolog)
login_argv[login_argc++] = "-f";
else
login_argv[login_argc++] = "--";
login_argv[login_argc++] = username;
}
login_argv[login_argc] = NULL; /* last login argv */
if (options.chroot) {
if (chroot(options.chroot) < 0)
@ -435,8 +446,87 @@ int main(int argc, char **argv)
}
/* Let the login program take care of password validation. */
execv(options.login, logarr);
log_err(_("%s: can't exec %s: %m"), options.tty, options.login);
execv(options.login, login_argv);
log_err(_("%s: can't exec %s: %m"), options.tty, login_argv[0]);
}
/*
* Returns : @str if \u not found
* : @username if @str equal to "\u"
* : newly allocated string if \u mixed with something other
*/
static char *replace_u(char *str, char *username)
{
char *entry = NULL, *p = str;
size_t usz = username ? strlen(username) : 0;
while (*p) {
size_t sz;
char *tp, *old = entry;
if (memcmp(p, "\\u", 2)) {
p++;
continue; /* no \u */
}
sz = strlen(str);
if (p == str && sz == 2)
/* 'str' contains only '\u' */
return username;
tp = entry = malloc(sz + usz);
if (!tp)
log_err(_("failed to allocate memory: %m"));
if (p != str) {
/* copy chars befor \u */
memcpy(tp, str, p - str);
tp += p - str;
}
if (usz) {
/* copy username */
memcpy(tp, username, usz);
tp += usz;
}
if (*(p + 2))
/* copy chars after \u + \0 */
memcpy(tp, p + 2, sz - (p - str) - 1);
else
*tp = '\0';
p = tp;
str = entry;
free(old);
}
return entry ? entry : str;
}
static void login_options_to_argv(char *argv[], int *argc,
char *str, char *username)
{
char *p;
int i = *argc;
while (str && isspace(*str))
str++;
p = str;
while (p && *p && i < LOGIN_ARGV_MAX) {
if (isspace(*p)) {
*p = '\0';
while (isspace(*++p))
;
if (*p) {
argv[i++] = replace_u(str, username);
str = p;
}
} else
p++;
}
if (str && *str && i < LOGIN_ARGV_MAX)
argv[i++] = replace_u(str, username);
*argc = i;
}
/* Parse command-line arguments. */
@ -1833,12 +1923,13 @@ static ssize_t append(char *dest, size_t len, const char *sep, const char *src)
return dsz + ssz + sz;
}
/*
* Do not allow the user to pass an option as a user name
* To be more safe: Use `--' to make sure the rest is
* interpreted as non-options by the program, if it supports it.
*/
static void checkname(const char* nm)
static void check_username(const char* nm)
{
const char *p = nm;
if (!nm)
@ -1855,48 +1946,3 @@ err:
log_err("checkname: %m");
}
static void replacename(char** arr, const char* nm)
{
const char *p;
char *tmp;
while ((p = *arr)) {
const char *p1 = p;
while (*p1) {
if (memcmp(p1, "\\u", 2) == 0) {
tmp = malloc(strlen(p) + strlen(nm));
if (!tmp)
log_err(_("failed to allocate memory: %m"));
if (p1 != p)
memcpy(tmp, p, (p1 - p));
*(tmp + (p1 - p)) = 0;
strcat(tmp, nm);
strcat(tmp, p1+2);
*arr = tmp;
}
p1++;
}
arr++;
}
}
static void mkarray(char** arr, char* str)
{
char* p = str;
char* start = p;
int i = 0;
while (*p && i < ARRAY_SIZE_MAX) {
if (isspace(*p)) {
*p = 0;
while (isspace(*++p))
;
if (*p) {
arr[i++] = start;
start = p;
}
} else
p++;
}
arr[i++] = start;
arr[i++] = (char*) 0;
}