[Libguestfs] [libguestfs-common PATCH v2 2/2] options/keys: introduce unescape_device_mapper_lvm()

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 <lersek(a)redhat.com&gt; --- 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; + } + } +} + 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;