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

On Mon, May 15, 2023 at 07:49:24PM +0200, Laszlo Ersek wrote: > 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. Libguestfs uses the /dev/VG/LV format internally, for > identifying devices, but the user might want to specify the > /dev/mapper/VG-LV ID format with the "--key ID:..." options. > > 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: > 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 | 86 ++++++++++++++++++++ > 1 file changed, 86 insertions(+) > > diff --git a/options/keys.c b/options/keys.c > index bc7459749276..f0164a6ed987 100644 > --- a/options/keys.c > +++ b/options/keys.c > @@ -27,6 +27,7 @@ > #include <errno.h> > #include <error.h> > #include <assert.h> > +#include <regex.h> > > #include "guestfs.h" > > @@ -260,6 +261,90 @@ key_store_add_from_selector (struct key_store *ks, const char *selector) > return key_store_import_key (ks, &key); > } > > +/* A /dev/mapper/ escaped character is: > + * - either any character except a slash or a hyphen, > + * - or a double hyphen. > + * > + * Note that parens are deliberately not included here -- they will be included > + * in the full pattern, for making them more easily countable. > + * > + * Also note that the bracket expression below does not contain a range > + * expression, therefore it should not be locale-sensitive. > + */ > +#define ESC_CH "[^-/]|--" > + > +/* Turn /dev/mapper/VG-LV into /dev/VG/LV. */ > +static void > +unescape_device_mapper_lvm (char *id) > +{ > + static bool compiled; > + int rc; > + static regex_t regex; > + regmatch_t match[5]; > + char *output; > + const char *vg_start, *vg_end, *lv_start, *lv_end; > + const char *input; > + > + if (!compiled) { > + /* Recognize /dev/mapper/VG-LV pathnames, where VG and LV don't contain > + * slashes, plus any original hyphens in them are doubled for escaping. > + */ > + static const char pattern[] = "^/dev/(" > + "mapper/" > + "((" ESC_CH ")+)" > + "-" > + "((" ESC_CH ")+)" > + ")$"; > + > + rc = regcomp (&regex, pattern, REG_EXTENDED); > + if (rc != 0) { > + char errbuf[256]; > + > + /* When regcomp() fails, the contents of "regex" are undefined, so we > + * cannot pass "regex" to regerror(). > + */ > + (void)regerror (rc, NULL, errbuf, sizeof errbuf); > + error (EXIT_FAILURE, 0, > + _("%s: Failed to compile pattern (%s). Please report a bug for " > + "libguestfs -- refer to guestfs(3) section BUGS."), > + __func__, errbuf); > + } > + compiled = true; > + } Any reason not to use PCRE and the COMPILE_REGEXP macro?

We also have macros like CLEANUP_PCRE2_MATCH_DATA_FREE to free match data automaticaly.

In general PCRE regexps are a lot more usable than the POSIX stuff.

Rich. > + rc = regexec (&regex, id, 5, match, 0); > + > + /* If there's no match, just leave "id" alone. */ > + if (rc != 0) > + return; > + > + /* Start outputting after "/dev/". */ > + output = id + match[1].rm_so; > + vg_start = id + match[2].rm_so; > + vg_end = id + match[2].rm_eo; > + lv_start = id + match[4].rm_so; > + lv_end = id + match[4].rm_eo; > + > + /* Each of the following two loops produces at most as many bytes as it > + * consumes, so we unescape "id" in-place. > + */ > + input = vg_start; > + while (input < vg_end) > + if ((*output++ = *input++) == '-') > + input++; > + > + *output++ = '/'; > + > + input = lv_start; > + while (input < lv_end) > + if ((*output++ = *input++) == '-') > + input++; > + > + *output++ = '\0'; > +} > + > +#undef ESC_CH > + > struct key_store * > key_store_import_key (struct key_store *ks, struct key_store_key *key) > { > @@ -278,6 +363,7 @@ 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; > > _______________________________________________ > Libguestfs mailing list > Libguestfs(a)redhat.com > https://listman.redhat.com/mailman/listinfo/libguestfs