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ITS#9437 Implement TOTP drift correction
This commit is contained in:
Ondřej Kuzník
Quanah Gibson-Mount
parent
87f3bad8bb
commit
fe7e4697e9
@ -119,9 +119,14 @@ The length of the time-step period for TOTP calculation.
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.B oathTOTPLastTimeStep: <number>
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The order of the last TOTP token successfully redeemed by the user.
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.TP
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.B oathTOTPGrace: <number>
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.B oathTOTPTimeStepWindow: <number>
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The number of time periods around the current time to try when checking the
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password provided by the user.
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.TP
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.B oathTOTPTimeStepDrift: <number>
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If the client didn't provide the correct token but it still fit with
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oathTOTPTimeStepWindow above, this attribute records the current offset to
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provide for slow clock drift of the client device.
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.RE
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.SH "SEE ALSO"
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@ -130,6 +130,7 @@ AttributeDescription *ad_oathTOTPParams;
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AttributeDescription *ad_oathTOTPToken;
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AttributeDescription *ad_oathTOTPLastTimeStep;
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AttributeDescription *ad_oathTOTPTimeStepWindow;
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AttributeDescription *ad_oathTOTPTimeStepDrift;
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static struct otp_at {
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char *schema;
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@ -327,7 +328,8 @@ static struct otp_at {
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"DESC 'OATH-LDAP: Last observed time step shift seen for TOTP' "
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"X-ORIGIN 'OATH-LDAP' "
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"SINGLE-VALUE "
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"SUP oathCounter )" },
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"SUP oathCounter )",
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&ad_oathTOTPTimeStepDrift },
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{ "( oath-ldap-at:11 "
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"NAME 'oathSecretLength' "
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@ -452,7 +454,7 @@ static struct otp_oc {
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"AUXILIARY "
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"SUP oathParams "
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"MUST ( oathTOTPTimeStepPeriod ) "
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"MAY ( oathTOTPTimeStepWindow $ oathTOTPTimeStepDrift ) )",
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"MAY ( oathTOTPTimeStepWindow ) )",
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&oc_oathTOTPParams },
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{ "( oath-ldap-oc:3 "
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"NAME 'oathToken' "
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@ -476,7 +478,7 @@ static struct otp_oc {
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"X-ORIGIN 'OATH-LDAP' "
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"AUXILIARY "
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"SUP oathToken "
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"MAY ( oathTOTPParams $ oathTOTPLastTimeStep ) )",
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"MAY ( oathTOTPParams $ oathTOTPLastTimeStep $ oathTOTPTimeStepDrift ) )",
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&oc_oathTOTPToken },
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{ NULL }
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};
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@ -672,13 +674,14 @@ done:
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}
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static long
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otp_totp( Operation *op, Entry *token )
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otp_totp( Operation *op, Entry *token, long *drift )
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{
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char outbuf[MAX_DIGITS + 1];
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Entry *params = NULL;
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Attribute *a;
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BerValue *secret, client_otp;
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const void *mech;
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long t, last_step = -1, found = -1, window = 0;
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long t, last_step = -1, found = -1, window = 0, old_drift;
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int i, otp_len, time_step;
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a = attr_find( token->e_attrs, ad_oathSecret );
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@ -706,7 +709,6 @@ otp_totp( Operation *op, Entry *token )
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a->a_vals[0].bv_val );
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goto done;
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}
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t = op->o_time / time_step;
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a = attr_find( params->e_attrs, ad_oathTOTPTimeStepWindow );
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if ( a && lutil_atol( &window, a->a_vals[0].bv_val ) != 0 ) {
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@ -716,6 +718,16 @@ otp_totp( Operation *op, Entry *token )
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goto done;
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}
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a = attr_find( params->e_attrs, ad_oathTOTPTimeStepDrift );
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if ( a && lutil_atol( drift, a->a_vals[0].bv_val ) != 0 ) {
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Debug( LDAP_DEBUG_ANY, "otp_totp: "
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"could not parse oathTOTPTimeStepDrift value %s\n",
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a->a_vals[0].bv_val );
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goto done;
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}
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old_drift = *drift;
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t = op->o_time / time_step + *drift;
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a = attr_find( params->e_attrs, ad_oathOTPLength );
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if ( lutil_atoi( &otp_len, a->a_vals[0].bv_val ) != 0 ) {
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Debug( LDAP_DEBUG_ANY, "otp_totp: "
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@ -740,38 +752,32 @@ otp_totp( Operation *op, Entry *token )
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client_otp.bv_val = op->orb_cred.bv_val + op->orb_cred.bv_len - otp_len;
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/* If check succeeds, advance the step counter accordingly */
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for ( i = -window; i <= window; i++ ) {
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char outbuf[MAX_DIGITS + 1];
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/* Negation of A001057 series that enumerates all integers:
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* (0, -1, 1, -2, 2, ...) */
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for ( i = 0; i >= -window; i = ( i < 0 ) ? -i : ~i ) {
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BerValue out = { .bv_val = outbuf, .bv_len = sizeof(outbuf) };
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if ( t + i < 0 ) continue;
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if ( t + i <= last_step ) continue;
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generate( secret, t + i, otp_len, &out, mech );
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if ( !ber_bvcmp( &out, &client_otp ) ) {
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found = t + i;
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*drift = old_drift + i;
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/* Would we leak information if we stopped right now? */
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}
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}
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/* OTP check passed, trim the password */
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if ( found >= 0 ) {
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int offset = found - t;
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assert( found > last_step );
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if ( found <= last_step ) {
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/* Token re-used, refuse */
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found = -1;
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Debug( LDAP_DEBUG_TRACE, "%s client tried to reuse old TOTP token %s, offset %d\n",
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op->o_log_prefix, token->e_name.bv_val, offset );
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} else {
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/* OTP check passed, trim the password */
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op->orb_cred.bv_len -= otp_len;
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Debug( LDAP_DEBUG_TRACE, "%s TOTP token %s redeemed with offset %d\n",
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op->o_log_prefix, token->e_name.bv_val, offset );
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}
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} else {
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Debug( LDAP_DEBUG_TRACE, "%s TOTP token was not valid\n",
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op->o_log_prefix );
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op->orb_cred.bv_len -= otp_len;
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Debug( LDAP_DEBUG_TRACE, "%s TOTP token %s redeemed with new drift of %ld\n",
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op->o_log_prefix, token->e_name.bv_val, *drift );
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}
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done:
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memset( outbuf, 0, sizeof(outbuf) );
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if ( params ) {
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be_entry_release_r( op, params );
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}
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@ -784,9 +790,9 @@ otp_op_bind( Operation *op, SlapReply *rs )
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slap_overinst *on = (slap_overinst *)op->o_bd->bd_info;
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BerValue totpdn = BER_BVNULL, hotpdn = BER_BVNULL, ndn;
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Entry *user = NULL, *token = NULL;
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AttributeDescription *ad = NULL;
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AttributeDescription *ad = NULL, *drift_ad = NULL;
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Attribute *a;
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long t = -1;
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long t = -1, drift = 0;
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int rc = SLAP_CB_CONTINUE;
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if ( op->oq_bind.rb_method != LDAP_AUTH_SIMPLE ) {
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@ -818,7 +824,8 @@ otp_op_bind( Operation *op, SlapReply *rs )
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&token ) == LDAP_SUCCESS ) {
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ndn = totpdn;
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ad = ad_oathTOTPLastTimeStep;
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t = otp_totp( op, token );
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drift_ad = ad_oathTOTPTimeStepDrift;
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t = otp_totp( op, token, &drift );
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be_entry_release_r( op, token );
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token = NULL;
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}
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@ -832,27 +839,44 @@ otp_op_bind( Operation *op, SlapReply *rs )
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token = NULL;
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}
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/* If check succeeds, advance the step counter accordingly */
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/* If check succeeds, advance the step counter and drift accordingly */
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if ( t >= 0 ) {
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char outbuf[32];
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char outbuf[32], drift_buf[32];
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Operation op2;
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Opheader oh;
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Modifications mod;
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Modifications mod[2], *m = mod;
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SlapReply rs2 = { REP_RESULT };
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slap_callback cb = { .sc_response = &slap_null_cb };
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BerValue bv[2];
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BerValue bv[2], bv_drift[2];
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bv[0].bv_val = outbuf;
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bv[0].bv_len = snprintf( bv[0].bv_val, sizeof(outbuf), "%ld", t );
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BER_BVZERO( &bv[1] );
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mod.sml_numvals = 1;
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mod.sml_values = bv;
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mod.sml_nvalues = NULL;
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mod.sml_desc = ad;
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mod.sml_op = LDAP_MOD_REPLACE;
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mod.sml_flags = SLAP_MOD_INTERNAL;
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mod.sml_next = NULL;
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m->sml_numvals = 1;
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m->sml_values = bv;
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m->sml_nvalues = NULL;
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m->sml_desc = ad;
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m->sml_op = LDAP_MOD_REPLACE;
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m->sml_flags = SLAP_MOD_INTERNAL;
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if ( drift_ad ) {
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m->sml_next = &mod[1];
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bv_drift[0].bv_val = drift_buf;
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bv_drift[0].bv_len = snprintf(
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bv_drift[0].bv_val, sizeof(drift_buf), "%ld", drift );
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BER_BVZERO( &bv_drift[1] );
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m++;
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m->sml_numvals = 1;
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m->sml_values = bv_drift;
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m->sml_nvalues = NULL;
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m->sml_desc = drift_ad;
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m->sml_op = LDAP_MOD_REPLACE;
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m->sml_flags = SLAP_MOD_INTERNAL;
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}
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m->sml_next = NULL;
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op2 = *op;
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oh = *op->o_hdr;
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@ -861,7 +885,7 @@ otp_op_bind( Operation *op, SlapReply *rs )
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op2.o_callback = &cb;
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op2.o_tag = LDAP_REQ_MODIFY;
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op2.orm_modlist = &mod;
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op2.orm_modlist = mod;
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op2.o_dn = op->o_bd->be_rootdn;
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op2.o_ndn = op->o_bd->be_rootndn;
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op2.o_req_dn = ndn;
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