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Remove 'login' and 'newgrp' builtins: not sane default behaviour

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This commit removes the undocumented 'login' and 'newgrp' builtin
commands. They already stopped blocking shell functions by that
name by changing from special to regular builtins in 04b91718 (a
change I forgot to mention in that commit message), but there is
another obnoxious aspect to these: being glorified hooks into
'exec', they replaced your shell session with the external commands
by the same name. This makes argument and error checking
impossible, so if you made so much as a typo, you would be
immediately logged out.

Even if that behaviour is wanted by a few, having it as the default
is user-hostile enough to be called a bug. It also violates the
POSIX definition of the 'newgrp' utility which explicitly says that
it "shall create a new shell execution environment", not replace
the existing one.
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/newgrp.html

Users who do want this behaviour can easily restore it by setting:
	alias login='exec login'
	alias newgrp='exec newgrp'

src/cmd/ksh93/bltins/misc.c:
- As there is no more 'login' builtin, combine b_exec() and
  B_login() functions, which allows eliminating a few variables.
  Note that most of 'exec' was actually implemented in B_login()!

src/cmd/ksh93/data/builtins.c:
- Remove "login" and "newgrp" table entries.

src/cmd/ksh93/include/builtins.h:
- Remove SYSLOGIN parser ID. As this was the first, all the others
  needed renumbering.

src/cmd/ksh93/sh/xec.c:
- Remove SYSLOGIN parser check that made 'login' and 'newgrp' act
  like 'exec' and replace the shell.
This commit is contained in:
Martijn Dekker 2020-06-12 06:57:57 +02:00
parent 7b82c338da
commit d8eba9d112
5 changed files with 56 additions and 63 deletions
Download patch file Download diff file Expand all files Collapse all files

68
src/cmd/ksh93/bltins/misc.c
View file

@ -60,6 +60,15 @@ struct login
char *arg0;
};
/*
* Handler function for nv_scan() that unsets a variable's export attribute
*/
static void noexport(register Namval_t* np, void *data)
{
NOT_USED(data);
nv_offattr(np,NV_EXPORT);
}
/*
* 'exec' special builtin and 'redirect' builtin
*/
@ -67,6 +76,9 @@ int b_exec(int argc,char *argv[], Shbltin_t *context)
{
struct login logdata;
register int n;
struct checkpt *pp;
const char *pname;
logdata.clear = 0;
logdata.arg0 = 0;
logdata.sh = context->shp;
@ -92,74 +104,54 @@ int b_exec(int argc,char *argv[], Shbltin_t *context)
if(*argv[0]=='r' && argv[opt_info.index]) /* 'redirect' supports no args */
errormsg(SH_DICT,ERROR_exit(2),e_badsyntax);
argv += opt_info.index;
if(*argv)
B_login(0,argv,(Shbltin_t*)&logdata);
return(0);
}
if(!*argv)
return(0);
static void noexport(register Namval_t* np, void *data)
{
NOT_USED(data);
nv_offattr(np,NV_EXPORT);
}
int B_login(int argc,char *argv[],Shbltin_t *context)
{
struct checkpt *pp;
register struct login *logp=0;
register Shell_t *shp;
const char *pname;
if(argc)
shp = context->shp;
else
{
logp = (struct login*)context;
shp = logp->sh;
}
pp = (struct checkpt*)shp->jmplist;
/* from here on, it's 'exec' with args, so we're replacing the shell */
if(sh_isoption(SH_RESTRICTED))
errormsg(SH_DICT,ERROR_exit(1),e_restricted,argv[0]);
else
{
register struct argnod *arg=shp->envlist;
register struct argnod *arg=logdata.sh->envlist;
register Namval_t* np;
register char *cp;
if(shp->subshell && !shp->subshare)
if(logdata.sh->subshell && !logdata.sh->subshare)
sh_subfork();
if(logp && logp->clear)
if(logdata.clear)
{
#ifdef _ENV_H
env_close(shp->env);
shp->env = env_open((char**)0,3);
env_close(logdata.sh->env);
logdata.sh->env = env_open((char**)0,3);
#else
nv_scan(shp->var_tree,noexport,0,NV_EXPORT,NV_EXPORT);
nv_scan(logdata.sh->var_tree,noexport,0,NV_EXPORT,NV_EXPORT);
#endif
}
while(arg)
{
if((cp=strchr(arg->argval,'=')) &&
(*cp=0,np=nv_search(arg->argval,shp->var_tree,0)))
(*cp=0,np=nv_search(arg->argval,logdata.sh->var_tree,0)))
{
nv_onattr(np,NV_EXPORT);
sh_envput(shp->env,np);
sh_envput(logdata.sh->env,np);
}
if(cp)
*cp = '=';
arg=arg->argnxt.ap;
}
pname = argv[0];
if(logp && logp->arg0)
argv[0] = logp->arg0;
if(logdata.arg0)
argv[0] = logdata.arg0;
#ifdef JOBS
if(job_close(shp) < 0)
if(job_close(logdata.sh) < 0)
return(1);
#endif /* JOBS */
/* force bad exec to terminate shell */
pp = (struct checkpt*)logdata.sh->jmplist;
pp->mode = SH_JMPEXIT;
sh_sigreset(2);
sh_freeup(shp);
path_exec(shp,pname,argv,NIL(struct argnod*));
sh_done(shp,0);
sh_freeup(logdata.sh);
path_exec(logdata.sh,pname,argv,NIL(struct argnod*));
sh_done(logdata.sh,0);
}
return(1);
}