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From:
Stefan Sperling <stsp@stsp.name>
Subject:
Re: Fix strftime(3) short buffer checks
To:
Josh Rickmar <joshrickmar@outlook.com>
Cc:
gameoftrees@openbsd.org
Date:
Sun, 21 Mar 2021 19:45:26 +0100

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On Sun, Mar 21, 2021 at 01:31:27PM -0400, Josh Rickmar wrote:
> Noticed this on the rebase/histedit -l patch.  Most likely copy pasted
> from elsewhere in the code.  Let's fix it everywhere.

Indeed, thanks! OK.

As much as I would like it, strftime doesn't use the same return
value semantics as snprintf/strlcpy :(

> -----------------------------------------------
> commit e046e6534160944f0b817685836911e37c93cbde (strftime)
> from: Josh Rickmar <jrick@companyzero.com>
> date: Sun Mar 21 17:28:36 2021 UTC
>  
>  Fix strftime(3) short buffer checks
>  
>  strftime(3) returns 0 if the buffer was too short to write the
>  complete string (including NUL) and will never return more than
>  maxsize-1.
>  
> diff 37e57951d24c69f2d56ab41065a2d5563d8174cb c40cf9c87952e14a1ebf8751b147f2c2f30102bd
> blob - 9bcd279e5446ef8a890025dd5e3e16b3206fc66a
> blob + 5a81fddc99d43b6d16f047c9a6ade37e0058f4e6
> --- got/got.c
> +++ got/got.c
> @@ -4570,7 +4570,7 @@ blame_cb(void *arg, int nlines, int lineno, struct got
>  	if (localtime_r(&committer_time, &tm) == NULL)
>  		return got_error_from_errno("localtime_r");
>  	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%G-%m-%d",
> -	    &tm) >= sizeof(bline->datebuf)) {
> +	    &tm) == 0) {
>  		err = got_error(GOT_ERR_NO_SPACE);
>  		goto done;
>  	}
> @@ -10073,7 +10073,7 @@ print_path_info(void *arg, const char *path, mode_t mo
>  	tm = localtime_r(&mtime, &mytm);
>  	if (tm == NULL)
>  		return NULL;
> -	if (strftime(datebuf, sizeof(datebuf), "%c %Z", tm) >= sizeof(datebuf))
> +	if (strftime(datebuf, sizeof(datebuf), "%c %Z", tm) == 0)
>  		return got_error(GOT_ERR_NO_SPACE);
>  	printf("timestamp: %s\n", datebuf);
>  
> blob - 5251b5a0c5366a6290eb08871fc51273ed568885
> blob + 3b1cd05a35ea3d8b66188660baf875aca5f0f005
> --- gotweb/gotweb.c
> +++ gotweb/gotweb.c
> @@ -3821,7 +3821,7 @@ gw_blame_cb(void *arg, int nlines, int lineno, struct 
>  	if (localtime_r(&committer_time, &tm) == NULL)
>  		return got_error_from_errno("localtime_r");
>  	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%G-%m-%d",
> -	    &tm) >= sizeof(bline->datebuf)) {
> +	    &tm) == 0) {
>  		err = got_error(GOT_ERR_NO_SPACE);
>  		goto done;
>  	}
> blob - 66c10afc613515bfc9122f54ffacf6671ce45f67
> blob + c426e9d11b25926d3d473cea50910a6e8ecd3240
> --- tog/tog.c
> +++ tog/tog.c
> @@ -1343,8 +1343,7 @@ draw_commit(struct tog_view *view, struct got_commit_o
>  	committer_time = got_object_commit_get_committer_time(commit);
>  	if (localtime_r(&committer_time, &tm) == NULL)
>  		return got_error_from_errno("localtime_r");
> -	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm)
> -	    >= sizeof(datebuf))
> +	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0)
>  		return got_error(GOT_ERR_NO_SPACE);
>  
>  	if (avail <= date_display_cols)
> 
>