On Thu, May 18, 2023 at 03:09:42PM +0200, Laszlo Ersek wrote:
> Libguestfs uses the
>
> /dev/VG/LV
>
> format internally, for identifying LVM logical volumes, but the user might
> want to specify the
>
> /dev/mapper/VG-LV ID
>
> format with the "--key ID:..." options.
>
> Introduce unescape_device_mapper_lvm() for turning
>
> /dev/mapper/VG-LV
>
> key IDs into
>
> /dev/VG/LV
>
> ones, unescaping doubled hyphens to single hyphens in both VG and LV in
> the process.
>
> Call unescape_device_mapper_lvm() from key_store_import_key(). That is,
> translate the ID as soon as the "--key" option is processed -- let the
> keystore only know about the usual /dev/VG/LV format, for later matching.
>
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2168506
> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
> ---
>
> Notes:
> v2:
>
> - rewrite without regular expressions [Rich, Laszlo]
>
> - restructure the commit message
>
> v1:
>
> regcomp() must definitely allocate memory dynamically, and we
> (intentionally) never free that -- we never call regfree(). I assume
> valgrind will catch this as a leak, so we might have to extend
> "valgrind-suppressions" in each dependent superproject. However, I'm
> unable to run "make check-valgrind" successfully in e.g. virt-v2v even
> before these patches; see also
> <https://listman.redhat.com/archives/libguestfs/2023-May/031496.html>.
>
> options/keys.c | 100 ++++++++++++++++++++
> 1 file changed, 100 insertions(+)
>
> diff --git a/options/keys.c b/options/keys.c
> index bc7459749276..52b27369016a 100644
> --- a/options/keys.c
> +++ b/options/keys.c
> @@ -260,6 +260,105 @@ key_store_add_from_selector (struct key_store *ks,
> const char *selector)
> return key_store_import_key (ks, &key);
> }
>
> +/* Turn /dev/mapper/VG-LV into /dev/VG/LV, in-place. */
> +static void
> +unescape_device_mapper_lvm (char *id)
> +{
> + static const char dev[] = "/dev/", dev_mapper[] = "/dev/mapper/";
> + const char *input_start;
> + char *output;
> + enum { M_SCAN, M_FILL, M_DONE } mode;
> +
> + if (!STRPREFIX (id, dev_mapper))
> + return;
> +
> + /* Start parsing "VG-LV" from "id" after "/dev/mapper/". */
> + input_start = id + (sizeof dev_mapper - 1);
> +
> + /* Start writing the unescaped "VG/LV" output after "/dev/". */
> + output = id + (sizeof dev - 1);
> +
> + for (mode = M_SCAN; mode < M_DONE; ++mode) {
> + char c;
> + const char *input = input_start;
> + const char *hyphen_buffered = NULL;
> + bool single_hyphen_seen = false;
> +
> + do {
> + c = *input;
> +
> + switch (c) {
> + case '-':
> + if (hyphen_buffered == NULL)
> + /* This hyphen may start an escaped hyphen, or it could be the
> + * separator in VG-LV.
> + */
> + hyphen_buffered = input;
> + else {
> + /* This hyphen completes an escaped hyphen; unescape it. */
> + if (mode == M_FILL)
> + *output++ = '-';
> + hyphen_buffered = NULL;
> + }
> + break;
> +
> + case '/':
> + /* Slash characters are forbidden in VG-LV anywhere. If there's any,
> + * we'll find it in the first (i.e., scanning) phase, before we
> output
> + * anything back to "id".
> + */
> + assert (mode == M_SCAN);
> + return;
> +
> + default:
> + /* Encountered a non-slash, non-hyphen character -- which also may be
> + * the terminating NUL.
> + */
> + if (hyphen_buffered != NULL) {
> + /* The non-hyphen character comes after a buffered hyphen, so the
> + * buffered hyphen is supposed to be the single hyphen that
> separates
> + * VG from LV in VG-LV. There are three requirements for this
> + * separator: (a) it must be unique (we must not have seen another
> + * such separator earlier), (b) it must not be at the start of
> VG-LV
> + * (because VG would be empty that way), (c) it must not be at the
> end
> + * of VG-LV (because LV would be empty that way). Should any of
> these
> + * be violated, we'll catch that during the first (i.e., scanning)
> + * phase, before modifying "id".
> + */
> + if (single_hyphen_seen || hyphen_buffered == input_start ||
> + c == '\0') {
> + assert (mode == M_SCAN);
> + return;
> + }
> +
> + /* Translate the separator hyphen to a slash character. */
> + if (mode == M_FILL)
> + *output++ = '/';
> + hyphen_buffered = NULL;
> + single_hyphen_seen = true;
> + }
> +
> + /* Output the non-hyphen character (including the terminating NUL)
> + * regardless of whether there was a buffered hyphen separator
> (which,
> + * by now, we'll have attempted to translate and flush).
> + */
> + if (mode == M_FILL)
> + *output++ = c;
> + }
> +
> + ++input;
> + } while (c != '\0');
> +
> + /* We must have seen the VG-LV separator. If that's not the case, we'll
> + * catch it before modifying "id".
> + */
> + if (!single_hyphen_seen) {
> + assert (mode == M_SCAN);
> + return;
> + }
> + }
> +}
So this code can never return an error? eg if the input was "A-B-C",
I think it would translate the string to "A/B-C" which is an output
but the input seems like it was wrong. Or is it that only the VG is
escaped? (I don't imagine there is some specification for /dev/mapper
device names.)
Rich.
> struct key_store *
> key_store_import_key (struct key_store *ks, struct key_store_key *key)
> {
> @@ -278,6 +377,7 @@ key_store_import_key (struct key_store *ks, struct
> key_store_key *key)
> error (EXIT_FAILURE, errno, "realloc");
>
> ks->keys = new_keys;
> + unescape_device_mapper_lvm (key->id);
> ks->keys[ks->nr_keys] = *key;
> ++ks->nr_keys;
>
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--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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