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Try to fix the old "he capability is stupid" bug in gettytab(5)/getty(8)

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There is one capability explicitly documented in gettytab(5) as stupid: he.
And it is indeed.  It was meant to facilitate system hostname modification,
but is hardly usable in practice because it allows very limited editing
(e.g., it depends on a particular hostname length, making it non-generic).

Replace it with simple implementation that treats ``he'' as POSIX extended
regular expression which is matched against the hostname.  If there are no
parenthesized subexpressions in the pattern, entire matched string is used
as the final hostname.  Otherwise, use the first matched subexpression.
If the pattern does not match, the original hostname is not modified.

Using regex(3) gives more freedom, does not complicate the code very much,
and makes a lot more sense, in turn making ``he'' less stupid and actually
useful (e.g., it is now possible to obtain node or domain names from the
original hostname string, without knowing it in advance).

Reviewed by:		jilles, manpages (wblock)
Approved by:		jilles (implied)
Differential Revision:	https://reviews.freebsd.org/D9244
This commit is contained in:
Alexey Dokuchaev 2017-02-02 20:30:50 +00:00
parent b3d5213675
commit f73ff060d2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=313107
2 changed files with 48 additions and 52 deletions
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27
libexec/getty/gettytab.5
View File

@ -28,7 +28,7 @@
.\" from: @(#)gettytab.5 8.4 (Berkeley) 4/19/94
.\" $FreeBSD$
.\" "
.Dd April 19, 1994
.Dd February 2, 2017
.Dt GETTYTAB 5
.Os
.Sh NAME
@ -118,7 +118,7 @@ character
.Em NOT
hangup line on last close
.It "he str" Ta Dv NULL Ta
.No "hostname editing string"
.No "hostname editing regular expression"
.It "hn str hostname hostname"
.It "ht bool false terminal has real tabs"
.It "hw bool false do cts/rts hardware flow control"
@ -302,18 +302,13 @@ but may also be overridden by the
table entry.
In either case it may be edited with the
.Va \&he
string.
A '@' in the
.Va \&he
string causes one character from the real hostname to
be copied to the final hostname.
A '#' in the
.Va \&he
string causes the next character of the real hostname
to be skipped.
Each character that
is neither '@' nor '#' is copied into the final hostname.
Surplus '@' and '#' characters are ignored.
POSIX
.Dq extended
regular expression, which is matched against the hostname.
If there are no parenthesized subexpressions in the pattern,
the entire matched string is used as the final hostname;
otherwise, the first matched subexpression is used instead.
If the pattern does not match, the original hostname is not modified.
.It \&%t
The tty name.
.It "\&%m, \&%r, \&%s, \&%v"
@ -528,10 +523,6 @@ of the delay algorithms are not implemented.
The terminal driver should support sane delay settings.
.Pp
The
.Va \&he
capability is stupid.
.Pp
The
.Xr termcap 5
format is horrid, something more rational should
have been chosen.

73
libexec/getty/subr.c
View File

@ -43,6 +43,7 @@ static const char rcsid[] =
#include <sys/time.h>
#include <poll.h>
#include <regex.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
@ -53,8 +54,6 @@ static const char rcsid[] =
#include "pathnames.h"
#include "extern.h"
/*
* Get a table entry.
*/
@ -469,42 +468,48 @@ adelay(int ms, struct delayval *dp)
char editedhost[MAXHOSTNAMELEN];
void
edithost(const char *pat)
edithost(const char *pattern)
{
const char *host = HN;
char *res = editedhost;
regex_t regex;
regmatch_t *match;
int found;
if (!pat)
pat = "";
while (*pat) {
switch (*pat) {
if (pattern == NULL || *pattern == '\0')
goto copyasis;
if (regcomp(&regex, pattern, REG_EXTENDED) != 0)
goto copyasis;
case '#':
if (*host)
host++;
break;
case '@':
if (*host)
*res++ = *host++;
break;
default:
*res++ = *pat;
break;
}
if (res == &editedhost[sizeof editedhost - 1]) {
*res = '\0';
return;
}
pat++;
match = calloc(regex.re_nsub + 1, sizeof(*match));
if (match == NULL) {
regfree(&regex);
goto copyasis;
}
if (*host)
strncpy(res, host, sizeof editedhost - (res - editedhost) - 1);
else
*res = '\0';
editedhost[sizeof editedhost - 1] = '\0';
found = !regexec(&regex, HN, regex.re_nsub + 1, match, 0);
if (found) {
size_t subex, totalsize;
/*
* We found a match. If there were no parenthesized
* subexpressions in the pattern, use entire matched
* string as ``editedhost''; otherwise use the first
* matched subexpression.
*/
subex = !!regex.re_nsub;
totalsize = match[subex].rm_eo - match[subex].rm_so + 1;
strlcpy(editedhost, HN + match[subex].rm_so, totalsize >
sizeof(editedhost) ? sizeof(editedhost) : totalsize);
}
free(match);
regfree(&regex);
if (found)
return;
/*
* In case of any errors, or if the pattern did not match, pass
* the original hostname as is.
*/
copyasis:
strlcpy(editedhost, HN, sizeof(editedhost));
}
static struct speedtab {