On Tue, 2014-10-07 at 18:54 +0200, thierry bordaz wrote:
> On 10/07/2014 06:00 PM, Nathaniel McCallum wrote:
>
> > Attached is the latest patch. I believe this includes all of our
> > discussions up until this point. However, a few bits of additional
> > information are needed.
> >
> > First, I have renamed the plugin to ipa-otp-counter. I believe all
> > replay prevention work can land inside this plugin, so the name is
> > appropriate.
> >
> > Second, I uncovered a bug in 389 which prevents me from validating the
> > non-replication request in bepre. This is the reason for the additional
> > betxnpre callback. If the upstream 389 bug is fixed, we can merge this
> > check back into bepre. https://fedorahosted.org/389/ticket/47919
>
> Hi Nathaniel,
>
> Just a rapid question about that dependency on
> https://fedorahosted.org/389/ticket/47919.
> Using txnpreop_mod you manage to workaround the DS issue.
> Do you need a fix for the DS issue in 1.3.2 or can it be fixed
> in a later version ?
I would strongly prefer a fix ASAP.
> thanks
> thierry
> >
> > Third, I believe we are now handling replication correct. An error is
> > never returned. When a replication would cause the counter to decrease,
> > we remove all counter/watermark related mods from the operation. This
> > will allow the replication to apply without decrementing the value.
> > There is also a new bepost method which check to see if the replication
> > was discarded (via CSN) while having a higher counter value. If so, we
> > apply the higher counter value.
> >
> > Here is the scenario. Server X receives two quick authentications;
> > replications A and B are sent to server Y. Before server Y can process
> > server X's replications, an authentication is performed on server Y;
> > replication C is sent to server X. The following logic holds true:
> > * csnA < csnB < csnC
> > * valueA = valueC, valueB > valueC
> >
> > When server X receives replication C, ipa-otp-counter will strip out all
> > counter mod operations; applying the update but not the lower value. The
> > value of replication B is retained. This is the correct behavior.
> >
> > When server Y processes replications A and B, ipa-otp-counter will
> > detect that a higher value has a lower CSN and will manually set the
> > higher value (in bepost). This initiates replication D, which is sent to
> > server X. Here is the logic:
> > * csnA < csnB < csnC < csnD
> > * valueA = valueC, valueB = valueD, valueD > valueC
> >
> > Server X receives replication D. D has the highest CSN. It has the same
> > value as replication B (server X's current value). Because the values
> > are the same, ipa-otp-counter will strip all counter mod operations.
> > This reduces counter write contention which might become a problem in
> > N-way replication when N>2.
> >
> > On Fri, 2014-10-03 at 19:52 +0200, thierry bordaz wrote:
> > > Hello Nathaniel,
> > >
> > > An additional comment about the patch.
> > >
> > > When the new value is detected to be invalid, it is fixed by a
> > > repair operation (trigger_replication).
> > > I did test it and it is fine to update, with an internal
> > > operation, the same entry that is currently updated.
> > >
> > > Now if you apply the repair operation into a be_preop or a
> > > betxn_preop, when it returns from preop the txn of the current
> > > operation will overwrite the repaired value.
> > >
> > > An option is to register a bepost that checks the value from
> > > the original entry (SLAPI_ENTRY_PRE_OP) and post entry
> > > (SLAPI_ENTRY_POST_OP). Then this postop checks the
> > > orginal/final value and can trigger the repair op.
> > > This time being outside of the main operation txn, the repair
> > > op will be applied.
> > >
> > > thanks
> > > thierry
> > > On 09/29/2014 08:30 PM, Nathaniel McCallum wrote:
> > >
> > > > On Mon, 2014-09-22 at 09:32 -0400, Simo Sorce wrote:
> > > > > On Sun, 21 Sep 2014 22:33:47 -0400
> > > > > Nathaniel McCallum <npmccal...@redhat.com> wrote:
> > > > >
> > > > > Comments inline.
> > > > >
> > > > > > +
> > > > > > +#define ch_malloc(type) \
> > > > > > + (type*) slapi_ch_malloc(sizeof(type))
> > > > > > +#define ch_calloc(count, type) \
> > > > > > + (type*) slapi_ch_calloc(count, sizeof(type))
> > > > > > +#define ch_free(p) \
> > > > > > + slapi_ch_free((void**) &(p))
> > > > > please do not redefine slapi functions, it just makes it harder to
> > > > > know
> > > > > what you used.
> > > > >
> > > > >
> > > > > > +typedef struct {
> > > > > > + bool exists;
> > > > > > + long long value;
> > > > > > +} counter;
> > > > > please no typedefs of structures, use "struct counter { ... };" and
> > > > > reference it as "struct counter" in the code.
> > > > >
> > > > > Btw, FWIW you could use a value of -1 to indicate non-existence of the
> > > > > counter value, given counters can only be positive, this would avoid
> > > > > the need for a struct.
> > > > >
> > > > > > +static int
> > > > > > +send_error(Slapi_PBlock *pb, int rc, char *template, ...)
> > > > > > +{
> > > > > > + va_list ap;
> > > > > > + int res;
> > > > > > +
> > > > > > + va_start(ap, template);
> > > > > > + res = vsnprintf(NULL, 0, template, ap);
> > > > > > + va_end(ap);
> > > > > > +
> > > > > > + if (res > 0) {
> > > > > > + char str[res + 1];
> > > > > > +
> > > > > > + va_start(ap, template);
> > > > > > + res = vsnprintf(str, sizeof(str), template, ap);
> > > > > > + va_end(ap);
> > > > > > +
> > > > > > + if (res > 0)
> > > > > > + slapi_send_ldap_result(pb, rc, NULL, str, 0, NULL);
> > > > > > + }
> > > > > > +
> > > > > > + if (res <= 0)
> > > > > > + slapi_send_ldap_result(pb, rc, NULL, NULL, 0, NULL);
> > > > > > +
> > > > > > + slapi_pblock_set(pb, SLAPI_RESULT_CODE, &rc);
> > > > > > + return rc;
> > > > > > +}
> > > > > This function seem not really useful, you use send_error() only at the
> > > > > end of one single function where you could have the classic scheme of
> > > > > using a done: label and just use directly slapi_ch_smprintf. This
> > > > > would
> > > > > remove the need to use vsnprintf and all the va_ machinery which is
> > > > > more than 50% of this function.
> > > > >
> > > > >
> > > > > > +static long long
> > > > > > +get_value(const LDAPMod *mod, long long def)
> > > > > > +{
> > > > > > + const struct berval *bv;
> > > > > > + long long val;
> > > > > > +
> > > > > > + if (mod == NULL)
> > > > > > + return def;
> > > > > > +
> > > > > > + if (mod->mod_vals.modv_bvals == NULL)
> > > > > > + return def;
> > > > > > +
> > > > > > + bv = mod->mod_vals.modv_bvals[0];
> > > > > > + if (bv == NULL)
> > > > > > + return def;
> > > > > In general (here and elsewhere) I prefer to always use {} in if
> > > > > clauses.
> > > > > I have been bitten enough time by people adding an instruction that
> > > > > should be in the braces but forgot to add braces (defensive
> > > > > programming
> > > > > style). But up to you.
> > > > >
> > > > > > + char buf[bv->bv_len + 1];
> > > > > > + memcpy(buf, bv->bv_val, bv->bv_len);
> > > > > > + buf[sizeof(buf)-1] = '\0';
> > > > > > +
> > > > > > + val = strtoll(buf, NULL, 10);
> > > > > > + if (val == LLONG_MIN || val == LLONG_MAX)
> > > > > > + return def;
> > > > > > +
> > > > > > + return val;
> > > > > > +}
> > > > > > +
> > > > > > +static struct berval **
> > > > > > +make_berval_array(long long value)
> > > > > > +{
> > > > > > + struct berval **bvs;
> > > > > > +
> > > > > > + bvs = ch_calloc(2, struct berval*);
> > > > > > + bvs[0] = ch_malloc(struct berval);
> > > > > > + bvs[0]->bv_val = slapi_ch_smprintf("%lld", value);
> > > > > > + bvs[0]->bv_len = strlen(bvs[0]->bv_val);
> > > > > > +
> > > > > > + return bvs;
> > > > > > +}
> > > > > > +
> > > > > > +static LDAPMod *
> > > > > > +make_ldapmod(int op, const char *attr, long long value)
> > > > > > +{
> > > > > > + LDAPMod *mod;
> > > > > > +
> > > > > > + mod = (LDAPMod*) slapi_ch_calloc(1, sizeof(LDAPMod));
> > > > > > + mod->mod_op = op | LDAP_MOD_BVALUES;
> > > > > > + mod->mod_type = slapi_ch_strdup(attr);
> > > > > > + mod->mod_bvalues = make_berval_array(value);
> > > > > > +
> > > > > > + return mod;
> > > > > > +}
> > > > > > +
> > > > > > +static void
> > > > > > +convert_ldapmod_to_bval(LDAPMod *mod)
> > > > > > +{
> > > > > > + if (mod == NULL || (mod->mod_op & LDAP_MOD_BVALUES))
> > > > > > + return;
> > > > > > +
> > > > > > + mod->mod_op |= LDAP_MOD_BVALUES;
> > > > > > +
> > > > > > + if (mod->mod_values == NULL) {
> > > > > > + mod->mod_bvalues = NULL;
> > > > > > + return;
> > > > > > + }
> > > > > > +
> > > > > > + for (size_t i = 0; mod->mod_values[i] != NULL; i++) {
> > > > > > + struct berval *bv = ch_malloc(struct berval);
> > > > > > + bv->bv_val = mod->mod_values[i];
> > > > > > + bv->bv_len = strlen(bv->bv_val);
> > > > > > + mod->mod_bvalues[i] = bv;
> > > > > > + }
> > > > > > +}
> > > > > > +
> > > > > > +static counter
> > > > > > +get_counter(Slapi_Entry *entry, const char *attr)
> > > > > > +{
> > > > > > + Slapi_Attr *sattr = NULL;
> > > > > > +
> > > > > > + return (counter) {
> > > > > > + slapi_entry_attr_find(entry, attr, &sattr) == 0,
> > > > > > + slapi_entry_attr_get_longlong(entry, attr)
> > > > > > + };
> > > > > > +}
> > > > > > +
> > > > > > +static void
> > > > > > +berval_free_array(struct berval ***bvals)
> > > > > > +{
> > > > > > + for (size_t i = 0; (*bvals)[i] != NULL; i++) {
> > > > > > + ch_free((*bvals)[i]->bv_val);
> > > > > > + ch_free((*bvals)[i]);
> > > > > > + }
> > > > > > +
> > > > > > + slapi_ch_free((void**) bvals);
> > > > > > +}
> > > > > > +
> > > > > > +static bool
> > > > > > +is_replication(Slapi_PBlock *pb)
> > > > > > +{
> > > > > > + int repl = 0;
> > > > > > + slapi_pblock_get(pb, SLAPI_IS_REPLICATED_OPERATION, &repl);
> > > > > > + return repl != 0;
> > > > > > +}
> > > > > > +
> > > > > > +static const char *
> > > > > > +get_attribute(Slapi_Entry *entry)
> > > > > > +{
> > > > > > + static struct {
> > > > > > + const char *clss;
> > > > > > + const char *attr;
> > > > > > + } table[] = {
> > > > > > + { "ipatokenHOTP", "ipatokenHOTPcounter" },
> > > > > > + { "ipatokenTOTP", "ipatokenTOTPwatermark" },
> > > > > > + { NULL, NULL }
> > > > > > + };
> > > > > > +
> > > > > > + const char *attr = NULL;
> > > > > > + char **clsses = NULL;
> > > > > > +
> > > > > > + clsses = slapi_entry_attr_get_charray(entry, "objectClass");
> > > > > > + if (clsses == NULL)
> > > > > > + return NULL;
> > > > > > +
> > > > > > + for (size_t i = 0; attr == NULL && clsses[i] != NULL; i++) {
> > > > > > + for (size_t j = 0; attr == NULL && table[j].clss != NULL;
> > > > > > j++) {
> > > > > > + if (PL_strcasecmp(table[j].clss, clsses[i]) == 0)
> > > > > > + attr = table[j].attr;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + slapi_ch_array_free(clsses);
> > > > > > + return attr;
> > > > > > +}
> > > > > Can you put a comment here that explains what you are going to do in
> > > > > each cases in plain English ? This will help people in future figuring
> > > > > out if/how to modify the code or why something happens a specific way.
> > > > > It will also help the reviewer follow what is going on.
> > > > >
> > > > >
> > > > > > +static int
> > > > > > +preop_mod(Slapi_PBlock *pb)
> > > > > > +{
> > > > > > + size_t count = 0, attrs = 0, extras = 0;
> > > > > > + Slapi_Entry *entry = NULL;
> > > > > > + const char *attr = NULL;
> > > > > > + LDAPMod **inmods = NULL;
> > > > > > + LDAPMod **mods = NULL;
> > > > > > + counter ctr, orig;
> > > > > > +
> > > > > > + /* Get the input values. */
> > > > > > + slapi_pblock_get(pb, SLAPI_ENTRY_PRE_OP, &entry);
> > > > > > + slapi_pblock_get(pb, SLAPI_MODIFY_MODS, &inmods);
> > > > > > + if (entry == NULL || inmods == NULL)
> > > > > > + return 0;
> > > > > > +
> > > > > > + /* Get the attribute name. */
> > > > > > + attr = get_attribute(entry);
> > > > > > + if (attr == NULL)
> > > > > > + return 0; /* Not a token. */
> > > > > > +
> > > > > > + /* Count items. */
> > > > > > + while (inmods != NULL && inmods[count] != NULL) {
> > > > > ^^ this one would read much better as:
> > > > > for (count = 0; inmods[count] != NULL; count++) {
> > > > >
> > > > > You do not need to check for insmods != NULL as you already check for
> > > > > it and return 0 a few lines above.
> > > > >
> > > > > > + LDAPMod *mod = inmods[count++];
> > > > > > +
> > > > > > + if (PL_strcasecmp(mod->mod_type, attr) != 0)
> > > > > > + continue;
> > > > > > +
> > > > > > + attrs++;
> > > > > > + switch (mod->mod_op & LDAP_MOD_OP) {
> > > > > > + case LDAP_MOD_REPLACE:
> > > > > > + case LDAP_MOD_INCREMENT:
> > > > > > + extras++;
> > > > > > + break;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + /* Not operating on the counter/watermark. */
> > > > > > + if (attrs == 0)
> > > > > > + return 0;
> > > > > > +
> > > > > > + /* Get the counter. */
> > > > > > + orig = ctr = get_counter(entry, attr);
> > > > > > +
> > > > > > + /* Filter the modify operations. */
> > > > > > + mods = ch_calloc(count + extras + 1, LDAPMod*);
> > > > > > + for (size_t i = 0, j = 0; inmods != NULL && inmods[i] != NULL;
> > > > > > mods[j++] = inmods[i++]) {
> > > > > Please remove check for insmods != NULL, it is useless, and removing
> > > > > it
> > > > > will bring back the line under 80columns
> > > > >
> > > > > > + LDAPMod *mod = inmods[i];
> > > > > > +
> > > > > > + if (PL_strcasecmp(mod->mod_type, attr) != 0)
> > > > > > + continue;
> > > > > > +
> > > > > > + convert_ldapmod_to_bval(mod);
> > > > > > +
> > > > > > + switch (mod->mod_op & LDAP_MOD_OP) {
> > > > > > + case LDAP_MOD_DELETE:
> > > > > > + ctr.exists = false;
> > > > > > + if (mod->mod_bvalues != NULL && mod->mod_bvalues[0] ==
> > > > > > NULL)
> > > > > > + berval_free_array(&mod->mod_bvalues);
> > > > > > +
> > > > > > + if (is_replication(pb))
> > > > > > + berval_free_array(&mod->mod_bvalues);
> > > > > > +
> > > > > > + if (mod->mod_bvalues == NULL)
> > > > > > + mod->mod_bvalues = make_berval_array(ctr.value);
> > > > > > + break;
> > > > > I am not sure I understand this segment, why are you touching the
> > > > > delete operation outside of a replication event ?
> > > > > Doesn't this defeat and admin tool trying to correctly delete/add to
> > > > > avoid races ?
> > > > >
> > > > > > + case LDAP_MOD_INCREMENT:
> > > > > > + mods[j++] = make_ldapmod(LDAP_MOD_DELETE, attr,
> > > > > > ctr.value); +
> > > > > > + ctr.value += get_value(mod, 1);
> > > > > uhmmm if you had an ADD followed by INCREMENT operation, would this
> > > > > cause the value to become value*2+1 instead of just value+1 ?
> > > > >
> > > > > > + berval_free_array(&mod->mod_bvalues);
> > > > > > + mod->mod_op &= ~LDAP_MOD_OP;
> > > > > > + mod->mod_op |= LDAP_MOD_ADD;
> > > > > > + mod->mod_bvalues = make_berval_array(ctr.value);
> > > > > > + break;
> > > > > uhmm why are you converting mod_increment in all cases ? (including
> > > > > replication)
> > > > >
> > > > > > + case LDAP_MOD_REPLACE:
> > > > > > + if (ctr.exists)
> > > > > > + mods[j++] = make_ldapmod(LDAP_MOD_DELETE, attr,
> > > > > > ctr.value); +
> > > > > > + mod->mod_op &= ~LDAP_MOD_OP;
> > > > > > + mod->mod_op |= LDAP_MOD_ADD;
> > > > > same question here, why are you converting a replace coming from
> > > > > replication into a delete/add ?
> > > > >
> > > > > > + case LDAP_MOD_ADD:
> > > > > > + ctr.value = get_value(mod, 0);
> > > > > > + ctr.exists = true;
> > > > > > + break;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + /* Set the modified operations. */
> > > > > > + slapi_pblock_set(pb, SLAPI_MODIFY_MODS, mods);
> > > > > > + ch_free(inmods);
> > > > > > +
> > > > > > + /* Ensure we aren't deleting the counter. */
> > > > > > + if (orig.exists && !ctr.exists)
> > > > > > + return send_error(pb, LDAP_UNWILLING_TO_PERFORM,
> > > > > > + "Will not delete %s", attr);
> > > > > > +
> > > > > > + /* Ensure we aren't rolling back the counter. */
> > > > > > + if (orig.value > ctr.value)
> > > > > > + return send_error(pb, LDAP_UNWILLING_TO_PERFORM,
> > > > > > + "Will not decrement %s", attr);
> > > > > > +
> > > > > > + return 0;
> > > > > > +}
> > > > > see above about send_error().
> > > > >
> > > > > I think what is needed most is the comment that explains the process
> > > > > at the to of the main function.
> > > > >
> > > > > Simo.
> > > > All of the above are fixed.
> > > >
> > > > Also, I have addressed Thierry's concern about putting the plugin in
> > > > betxnpreoperation by splitting the plugin into two phases: modification
> > > > and validation. Now all modifications occur in bepreoperation and all
> > > > validation occurs in betxnpreoperation.
> > > >
> > > > Additionally, I have new code to trigger a new replication in the case
> > > > where a validation error occurs and we are in a replication transaction.
> > > > Thus, when A attempts to push an old counter value to B, B will now
> > > > replicate the latest value back to A.
> > > >
> > > > Nathaniel
> > > >
>
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