- djm@cvs.openbsd.org 2013/01/17 23:00:01

     [auth.c key.c key.h ssh-keygen.1 ssh-keygen.c sshd_config.5]
     [krl.c krl.h PROTOCOL.krl]
     add support for Key Revocation Lists (KRLs). These are a compact way to
     represent lists of revoked keys and certificates, taking as little as
     a single bit of incremental cost to revoke a certificate by serial number.
     KRLs are loaded via the existing RevokedKeys sshd_config option.
     feedback and ok markus@

1 files changed, 1227 insertions, 0 deletions

diff --git a/krl.c b/krl.c
new file mode 100644
index 000000000..485057029
--- /dev/null
+++ b/krl.c
@@ -0,0 +1,1227 @@
+/*
+ * Copyright (c) 2012 Damien Miller <djm@mindrot.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* $OpenBSD: krl.c,v 1.2 2013/01/18 00:24:58 djm Exp $ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/tree.h>
+#include <sys/queue.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "buffer.h"
+#include "key.h"
+#include "authfile.h"
+#include "err.h"
+#include "misc.h"
+#include "log.h"
+#include "xmalloc.h"
+
+#include "krl.h"
+
+/* #define DEBUG_KRL */
+#ifdef DEBUG_KRL
+# define KRL_DBG(x) debug3 x
+#else
+# define KRL_DBG(x)
+#endif
+
+/*
+ * Trees of revoked serial numbers, key IDs and keys. This allows
+ * quick searching, querying and producing lists in canonical order.
+ */
+
+/* Tree of serial numbers. XXX make smarter: really need a real sparse bitmap */
+struct revoked_serial {
+        u_int64_t lo, hi;
+        RB_ENTRY(revoked_serial) tree_entry;
+};
+static int serial_cmp(struct revoked_serial *a, struct revoked_serial *b);
+RB_HEAD(revoked_serial_tree, revoked_serial);
+RB_GENERATE_STATIC(revoked_serial_tree, revoked_serial, tree_entry, serial_cmp);
+
+/* Tree of key IDs */
+struct revoked_key_id {
+        char *key_id;
+        RB_ENTRY(revoked_key_id) tree_entry;
+};
+static int key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b);
+RB_HEAD(revoked_key_id_tree, revoked_key_id);
+RB_GENERATE_STATIC(revoked_key_id_tree, revoked_key_id, tree_entry, key_id_cmp);
+
+/* Tree of blobs (used for keys and fingerprints) */
+struct revoked_blob {
+        u_char *blob;
+        u_int len;
+        RB_ENTRY(revoked_blob) tree_entry;
+};
+static int blob_cmp(struct revoked_blob *a, struct revoked_blob *b);
+RB_HEAD(revoked_blob_tree, revoked_blob);
+RB_GENERATE_STATIC(revoked_blob_tree, revoked_blob, tree_entry, blob_cmp);
+
+/* Tracks revoked certs for a single CA */
+struct revoked_certs {
+        Key *ca_key;
+        struct revoked_serial_tree revoked_serials;
+        struct revoked_key_id_tree revoked_key_ids;
+        TAILQ_ENTRY(revoked_certs) entry;
+};
+TAILQ_HEAD(revoked_certs_list, revoked_certs);
+
+struct ssh_krl {
+        u_int64_t krl_version;
+        u_int64_t generated_date;
+        u_int64_t flags;
+        char *comment;
+        struct revoked_blob_tree revoked_keys;
+        struct revoked_blob_tree revoked_sha1s;
+        struct revoked_certs_list revoked_certs;
+};
+
+/* Return equal if a and b overlap */
+static int
+serial_cmp(struct revoked_serial *a, struct revoked_serial *b)
+{
+        if (a->hi >= b->lo && a->lo <= b->hi)
+                return 0;
+        return a->lo < b->lo ? -1 : 1;
+}
+
+static int
+key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b)
+{
+        return strcmp(a->key_id, b->key_id);
+}
+
+static int
+blob_cmp(struct revoked_blob *a, struct revoked_blob *b)
+{
+        int r;
+
+        if (a->len != b->len) {
+                if ((r = memcmp(a->blob, b->blob, MIN(a->len, b->len))) != 0)
+                        return r;
+                return a->len > b->len ? 1 : -1;
+        } else
+                return memcmp(a->blob, b->blob, a->len);
+}
+
+struct ssh_krl *
+ssh_krl_init(void)
+{
+        struct ssh_krl *krl;
+
+        if ((krl = calloc(1, sizeof(*krl))) == NULL)
+                return NULL;
+        RB_INIT(&krl->revoked_keys);
+        RB_INIT(&krl->revoked_sha1s);
+        TAILQ_INIT(&krl->revoked_certs);
+        return krl;
+}
+
+static void
+revoked_certs_free(struct revoked_certs *rc)
+{
+        struct revoked_serial *rs, *trs;
+        struct revoked_key_id *rki, *trki;
+
+        RB_FOREACH_SAFE(rs, revoked_serial_tree, &rc->revoked_serials, trs) {
+                RB_REMOVE(revoked_serial_tree, &rc->revoked_serials, rs);
+                free(rs);
+        }
+        RB_FOREACH_SAFE(rki, revoked_key_id_tree, &rc->revoked_key_ids, trki) {
+                RB_REMOVE(revoked_key_id_tree, &rc->revoked_key_ids, rki);
+                free(rki->key_id);
+                free(rki);
+        }
+        if (rc->ca_key != NULL)
+                key_free(rc->ca_key);
+}
+
+void
+ssh_krl_free(struct ssh_krl *krl)
+{
+        struct revoked_blob *rb, *trb;
+        struct revoked_certs *rc, *trc;
+
+        if (krl == NULL)
+                return;
+
+        free(krl->comment);
+        RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_keys, trb) {
+                RB_REMOVE(revoked_blob_tree, &krl->revoked_keys, rb);
+                free(rb->blob);
+                free(rb);
+        }
+        RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_sha1s, trb) {
+                RB_REMOVE(revoked_blob_tree, &krl->revoked_sha1s, rb);
+                free(rb->blob);
+                free(rb);
+        }
+        TAILQ_FOREACH_SAFE(rc, &krl->revoked_certs, entry, trc) {
+                TAILQ_REMOVE(&krl->revoked_certs, rc, entry);
+                revoked_certs_free(rc);
+        }
+}
+
+void
+ssh_krl_set_version(struct ssh_krl *krl, u_int64_t version)
+{
+        krl->krl_version = version;
+}
+
+void
+ssh_krl_set_comment(struct ssh_krl *krl, const char *comment)
+{
+        free(krl->comment);
+        if ((krl->comment = strdup(comment)) == NULL)
+                fatal("%s: strdup", __func__);
+}
+
+/*
+ * Find the revoked_certs struct for a CA key. If allow_create is set then
+ * create a new one in the tree if one did not exist already.
+ */
+static int
+revoked_certs_for_ca_key(struct ssh_krl *krl, const Key *ca_key,
+    struct revoked_certs **rcp, int allow_create)
+{
+        struct revoked_certs *rc;
+
+        *rcp = NULL;
+        TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
+                if (key_equal(rc->ca_key, ca_key)) {
+                        *rcp = rc;
+                        return 0;
+                }
+        }
+        if (!allow_create)
+                return 0;
+        /* If this CA doesn't exist in the list then add it now */
+        if ((rc = calloc(1, sizeof(*rc))) == NULL)
+                return -1;
+        if ((rc->ca_key = key_from_private(ca_key)) == NULL) {
+                free(rc);
+                return -1;
+        }
+        RB_INIT(&rc->revoked_serials);
+        RB_INIT(&rc->revoked_key_ids);
+        TAILQ_INSERT_TAIL(&krl->revoked_certs, rc, entry);
+        debug3("%s: new CA %s", __func__, key_type(ca_key));
+        *rcp = rc;
+        return 0;
+}
+
+static int
+insert_serial_range(struct revoked_serial_tree *rt, u_int64_t lo, u_int64_t hi)
+{
+        struct revoked_serial rs, *ers, *crs, *irs;
+
+        KRL_DBG(("%s: insert %llu:%llu", __func__, lo, hi));
+        bzero(&rs, sizeof(rs));
+        rs.lo = lo;
+        rs.hi = hi;
+        ers = RB_NFIND(revoked_serial_tree, rt, &rs);
+        if (ers == NULL || serial_cmp(ers, &rs) != 0) {
+                /* No entry matches. Just insert */
+                if ((irs = malloc(sizeof(rs))) == NULL)
+                        return -1;
+                memcpy(irs, &rs, sizeof(*irs));
+                ers = RB_INSERT(revoked_serial_tree, rt, irs);
+                if (ers != NULL) {
+                        KRL_DBG(("%s: bad: ers != NULL", __func__));
+                        /* Shouldn't happen */
+                        free(ers);
+                        return -1;
+                }
+                ers = irs;
+        } else {
+                KRL_DBG(("%s: overlap found %llu:%llu", __func__,
+                    ers->lo, ers->hi));
+                /*
+                 * The inserted entry overlaps an existing one. Grow the
+                 * existing entry.
+                 */
+                if (ers->lo > lo)
+                        ers->lo = lo;
+                if (ers->hi < hi)
+                        ers->hi = hi;
+        }
+        /*
+         * The inserted or revised range might overlap or abut adjacent ones;
+         * coalesce as necessary.
+         */
+
+        /* Check predecessors */
+        while ((crs = RB_PREV(revoked_serial_tree, rt, ers)) != NULL) {
+                KRL_DBG(("%s: pred %llu:%llu", __func__, crs->lo, crs->hi));
+                if (ers->lo != 0 && crs->hi < ers->lo - 1)
+                        break;
+                /* This entry overlaps. */
+                if (crs->lo < ers->lo) {
+                        ers->lo = crs->lo;
+                        KRL_DBG(("%s: pred extend %llu:%llu", __func__,
+                            ers->lo, ers->hi));
+                }
+                RB_REMOVE(revoked_serial_tree, rt, crs);
+                free(crs);
+        }
+        /* Check successors */
+        while ((crs = RB_NEXT(revoked_serial_tree, rt, ers)) != NULL) {
+                KRL_DBG(("%s: succ %llu:%llu", __func__, crs->lo, crs->hi));
+                if (ers->hi != (u_int64_t)-1 && crs->lo > ers->hi + 1)
+                        break;
+                /* This entry overlaps. */
+                if (crs->hi > ers->hi) {
+                        ers->hi = crs->hi;
+                        KRL_DBG(("%s: succ extend %llu:%llu", __func__,
+                            ers->lo, ers->hi));
+                }
+                RB_REMOVE(revoked_serial_tree, rt, crs);
+                free(crs);
+        }
+        KRL_DBG(("%s: done, final %llu:%llu", __func__, ers->lo, ers->hi));
+        return 0;
+}
+
+int
+ssh_krl_revoke_cert_by_serial(struct ssh_krl *krl, const Key *ca_key,
+    u_int64_t serial)
+{
+        return ssh_krl_revoke_cert_by_serial_range(krl, ca_key, serial, serial);
+}
+
+int
+ssh_krl_revoke_cert_by_serial_range(struct ssh_krl *krl, const Key *ca_key,
+    u_int64_t lo, u_int64_t hi)
+{
+        struct revoked_certs *rc;
+
+        if (lo > hi || lo == 0)
+                return -1;
+        if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0)
+                return -1;
+        return insert_serial_range(&rc->revoked_serials, lo, hi);
+}
+
+int
+ssh_krl_revoke_cert_by_key_id(struct ssh_krl *krl, const Key *ca_key,
+    const char *key_id)
+{
+        struct revoked_key_id *rki, *erki;
+        struct revoked_certs *rc;
+
+        if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0)
+                return -1;
+
+        debug3("%s: revoke %s", __func__, key_id);
+        if ((rki = calloc(1, sizeof(*rki))) == NULL ||
+            (rki->key_id = strdup(key_id)) == NULL) {
+                free(rki);
+                fatal("%s: strdup", __func__);
+        }
+        erki = RB_INSERT(revoked_key_id_tree, &rc->revoked_key_ids, rki);
+        if (erki != NULL) {
+                free(rki->key_id);
+                free(rki);
+        }
+        return 0;
+}
+
+/* Convert "key" to a public key blob without any certificate information */
+static int
+plain_key_blob(const Key *key, u_char **blob, u_int *blen)
+{
+        Key *kcopy;
+        int r;
+
+        if ((kcopy = key_from_private(key)) == NULL)
+                return -1;
+        if (key_is_cert(kcopy)) {
+                if (key_drop_cert(kcopy) != 0) {
+                        error("%s: key_drop_cert", __func__);
+                        key_free(kcopy);
+                        return -1;
+                }
+        }
+        r = key_to_blob(kcopy, blob, blen);
+        free(kcopy);
+        return r == 0 ? -1 : 0;
+}
+
+/* Revoke a key blob. Ownership of blob is transferred to the tree */
+static int
+revoke_blob(struct revoked_blob_tree *rbt, u_char *blob, u_int len)
+{
+        struct revoked_blob *rb, *erb;
+
+        if ((rb = calloc(1, sizeof(*rb))) == NULL)
+                return -1;
+        rb->blob = blob;
+        rb->len = len;
+        erb = RB_INSERT(revoked_blob_tree, rbt, rb);
+        if (erb != NULL) {
+                free(rb->blob);
+                free(rb);
+        }
+        return 0;
+}
+
+int
+ssh_krl_revoke_key_explicit(struct ssh_krl *krl, const Key *key)
+{
+        u_char *blob;
+        u_int len;
+
+        debug3("%s: revoke type %s", __func__, key_type(key));
+        if (plain_key_blob(key, &blob, &len) != 0)
+                return -1;
+        return revoke_blob(&krl->revoked_keys, blob, len);
+}
+
+int
+ssh_krl_revoke_key_sha1(struct ssh_krl *krl, const Key *key)
+{
+        u_char *blob;
+        u_int len;
+
+        debug3("%s: revoke type %s by sha1", __func__, key_type(key));
+        if ((blob = key_fingerprint_raw(key, SSH_FP_SHA1, &len)) == NULL)
+                return -1;
+        return revoke_blob(&krl->revoked_sha1s, blob, len);
+}
+
+int
+ssh_krl_revoke_key(struct ssh_krl *krl, const Key *key)
+{
+        if (!key_is_cert(key))
+                return ssh_krl_revoke_key_sha1(krl, key);
+
+        if (key_cert_is_legacy(key) || key->cert->serial == 0) {
+                return ssh_krl_revoke_cert_by_key_id(krl,
+                    key->cert->signature_key,
+                    key->cert->key_id);
+        } else {
+                return ssh_krl_revoke_cert_by_serial(krl,
+                    key->cert->signature_key,
+                    key->cert->serial);
+        }
+}
+
+/*
+ * Select a copact next section type to emit in a KRL based on the
+ * current section type, the run length of contiguous revoked serial
+ * numbers and the gaps from the last and to the next revoked serial.
+ * Applies a mostly-accurate bit cost model to select the section type
+ * that will minimise the size of the resultant KRL.
+ */
+static int
+choose_next_state(int current_state, u_int64_t contig, int final,
+    u_int64_t last_gap, u_int64_t next_gap, int *force_new_section)
+{
+        int new_state;
+        u_int64_t cost, cost_list, cost_range, cost_bitmap, cost_bitmap_restart;
+
+        /*
+         * Avoid unsigned overflows.
+         * The limits are high enough to avoid confusing the calculations.
+         */
+        contig = MIN(contig, 1ULL<<31);
+        last_gap = MIN(last_gap, 1ULL<<31);
+        next_gap = MIN(next_gap, 1ULL<<31);
+
+        /*
+         * Calculate the cost to switch from the current state to candidates.
+         * NB. range sections only ever contain a single range, so their
+         * switching cost is independent of the current_state.
+         */
+        cost_list = cost_bitmap = cost_bitmap_restart = 0;
+        cost_range = 8;
+        switch (current_state) {
+        case KRL_SECTION_CERT_SERIAL_LIST:
+                cost_bitmap_restart = cost_bitmap = 8 + 64;
+                break;
+        case KRL_SECTION_CERT_SERIAL_BITMAP:
+                cost_list = 8;
+                cost_bitmap_restart = 8 + 64;
+                break;
+        case KRL_SECTION_CERT_SERIAL_RANGE:
+        case 0:
+                cost_bitmap_restart = cost_bitmap = 8 + 64;
+                cost_list = 8;
+        }
+
+        /* Estimate base cost in bits of each section type */
+        cost_list += 64 * contig + (final ? 0 : 8+64);
+        cost_range += (2 * 64) + (final ? 0 : 8+64);
+        cost_bitmap += last_gap + contig + (final ? 0 : MIN(next_gap, 8+64));
+        cost_bitmap_restart += contig + (final ? 0 : MIN(next_gap, 8+64));
+
+        /* Convert to byte costs for actual comparison */
+        cost_list = (cost_list + 7) / 8;
+        cost_bitmap = (cost_bitmap + 7) / 8;
+        cost_bitmap_restart = (cost_bitmap_restart + 7) / 8;
+        cost_range = (cost_range + 7) / 8;
+
+        /* Now pick the best choice */
+        *force_new_section = 0;
+        new_state = KRL_SECTION_CERT_SERIAL_BITMAP;
+        cost = cost_bitmap;
+        if (cost_range < cost) {
+                new_state = KRL_SECTION_CERT_SERIAL_RANGE;
+                cost = cost_range;
+        }
+        if (cost_list < cost) {
+                new_state = KRL_SECTION_CERT_SERIAL_LIST;
+                cost = cost_list;
+        }
+        if (cost_bitmap_restart < cost) {
+                new_state = KRL_SECTION_CERT_SERIAL_BITMAP;
+                *force_new_section = 1;
+                cost = cost_bitmap_restart;
+        }
+        debug3("%s: contig %llu last_gap %llu next_gap %llu final %d, costs:"
+            "list %llu range %llu bitmap %llu new bitmap %llu, "
+            "selected 0x%02x%s", __func__, contig, last_gap, next_gap, final,
+            cost_list, cost_range, cost_bitmap, cost_bitmap_restart, new_state,
+            *force_new_section ? " restart" : "");
+        return new_state;
+}
+
+/* Generate a KRL_SECTION_CERTIFICATES KRL section */
+static int
+revoked_certs_generate(struct revoked_certs *rc, Buffer *buf)
+{
+        int final, force_new_sect, r = -1;
+        u_int64_t i, contig, gap, last = 0, bitmap_start = 0;
+        struct revoked_serial *rs, *nrs;
+        struct revoked_key_id *rki;
+        int next_state, state = 0;
+        Buffer sect;
+        u_char *kblob = NULL;
+        u_int klen;
+        BIGNUM *bitmap = NULL;
+
+        /* Prepare CA scope key blob if we have one supplied */
+        if (key_to_blob(rc->ca_key, &kblob, &klen) == 0)
+                return -1;
+
+        buffer_init(&sect);
+
+        /* Store the header */
+        buffer_put_string(buf, kblob, klen);
+        buffer_put_string(buf, NULL, 0); /* Reserved */
+
+        free(kblob);
+
+        /* Store the revoked serials.  */
+        for (rs = RB_MIN(revoked_serial_tree, &rc->revoked_serials);
+             rs != NULL;
+             rs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs)) {
+                debug3("%s: serial %llu:%llu state 0x%02x", __func__,
+                    rs->lo, rs->hi, state);
+
+                /* Check contiguous length and gap to next section (if any) */
+                nrs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs);
+                final = nrs == NULL;
+                gap = nrs == NULL ? 0 : nrs->lo - rs->hi;
+                contig = 1 + (rs->hi - rs->lo);
+
+                /* Choose next state based on these */
+                next_state = choose_next_state(state, contig, final,
+                    state == 0 ? 0 : rs->lo - last, gap, &force_new_sect);
+
+                /*
+                 * If the current section is a range section or has a different
+                 * type to the next section, then finish it off now.
+                 */
+                if (state != 0 && (force_new_sect || next_state != state ||
+                    state == KRL_SECTION_CERT_SERIAL_RANGE)) {
+                        debug3("%s: finish state 0x%02x", __func__, state);
+                        switch (state) {
+                        case KRL_SECTION_CERT_SERIAL_LIST:
+                        case KRL_SECTION_CERT_SERIAL_RANGE:
+                                break;
+                        case KRL_SECTION_CERT_SERIAL_BITMAP:
+                                buffer_put_bignum2(&sect, bitmap);
+                                BN_free(bitmap);
+                                bitmap = NULL;
+                                break;
+                        }
+                        buffer_put_char(buf, state);
+                        buffer_put_string(buf,
+                            buffer_ptr(&sect), buffer_len(&sect));
+                }
+
+                /* If we are starting a new section then prepare it now */
+                if (next_state != state || force_new_sect) {
+                        debug3("%s: start state 0x%02x", __func__, next_state);
+                        state = next_state;
+                        buffer_clear(&sect);
+                        switch (state) {
+                        case KRL_SECTION_CERT_SERIAL_LIST:
+                        case KRL_SECTION_CERT_SERIAL_RANGE:
+                                break;
+                        case KRL_SECTION_CERT_SERIAL_BITMAP:
+                                if ((bitmap = BN_new()) == NULL)
+                                        goto out;
+                                bitmap_start = rs->lo;
+                                buffer_put_int64(&sect, bitmap_start);
+                                break;
+                        }
+                }
+
+                /* Perform section-specific processing */
+                switch (state) {
+                case KRL_SECTION_CERT_SERIAL_LIST:
+                        for (i = rs->lo; i < contig; i++)
+                                buffer_put_int64(&sect, rs->lo + i);
+                        break;
+                case KRL_SECTION_CERT_SERIAL_RANGE:
+                        buffer_put_int64(&sect, rs->lo);
+                        buffer_put_int64(&sect, rs->hi);
+                        break;
+                case KRL_SECTION_CERT_SERIAL_BITMAP:
+                        if (rs->lo - bitmap_start > INT_MAX) {
+                                error("%s: insane bitmap gap", __func__);
+                                goto out;
+                        }
+                        for (i = 0; i < contig; i++) {
+                                if (BN_set_bit(bitmap,
+                                    rs->lo + i - bitmap_start) != 1)
+                                        goto out;
+                        }
+                        break;
+                }
+                last = rs->hi;
+        }
+        /* Flush the remaining section, if any */
+        if (state != 0) {
+                debug3("%s: serial final flush for state 0x%02x",
+                    __func__, state);
+                switch (state) {
+                case KRL_SECTION_CERT_SERIAL_LIST:
+                case KRL_SECTION_CERT_SERIAL_RANGE:
+                        break;
+                case KRL_SECTION_CERT_SERIAL_BITMAP:
+                        buffer_put_bignum2(&sect, bitmap);
+                        BN_free(bitmap);
+                        bitmap = NULL;
+                        break;
+                }
+                buffer_put_char(buf, state);
+                buffer_put_string(buf,
+                    buffer_ptr(&sect), buffer_len(&sect));
+        }
+        debug3("%s: serial done ", __func__);
+
+        /* Now output a section for any revocations by key ID */
+        buffer_clear(&sect);
+        RB_FOREACH(rki, revoked_key_id_tree, &rc->revoked_key_ids) {
+                debug3("%s: key ID %s", __func__, rki->key_id);
+                buffer_put_cstring(&sect, rki->key_id);
+        }
+        if (buffer_len(&sect) != 0) {
+                buffer_put_char(buf, KRL_SECTION_CERT_KEY_ID);
+                buffer_put_string(buf, buffer_ptr(&sect),
+                    buffer_len(&sect));
+        }
+        r = 0;
+ out:
+        if (bitmap != NULL)
+                BN_free(bitmap);
+        buffer_free(&sect);
+        return r;
+}
+
+int
+ssh_krl_to_blob(struct ssh_krl *krl, Buffer *buf, const Key **sign_keys,
+    u_int nsign_keys)
+{
+        int r = -1;
+        struct revoked_certs *rc;
+        struct revoked_blob *rb;
+        Buffer sect;
+        u_char *kblob = NULL, *sblob = NULL;
+        u_int klen, slen, i;
+
+        if (krl->generated_date == 0)
+                krl->generated_date = time(NULL);
+
+        buffer_init(&sect);
+
+        /* Store the header */
+        buffer_append(buf, KRL_MAGIC, sizeof(KRL_MAGIC) - 1);
+        buffer_put_int(buf, KRL_FORMAT_VERSION);
+        buffer_put_int64(buf, krl->krl_version);
+        buffer_put_int64(buf, krl->generated_date);
+        buffer_put_int64(buf, krl->flags);
+        buffer_put_string(buf, NULL, 0);
+        buffer_put_cstring(buf, krl->comment ? krl->comment : "");
+
+        /* Store sections for revoked certificates */
+        TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
+                if (revoked_certs_generate(rc, &sect) != 0)
+                        goto out;
+                buffer_put_char(buf, KRL_SECTION_CERTIFICATES);
+                buffer_put_string(buf, buffer_ptr(&sect),
+                    buffer_len(&sect));
+        }
+
+        /* Finally, output sections for revocations by public key/hash */
+        buffer_clear(&sect);
+        RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_keys) {
+                debug3("%s: key len %u ", __func__, rb->len);
+                buffer_put_string(&sect, rb->blob, rb->len);
+        }
+        if (buffer_len(&sect) != 0) {
+                buffer_put_char(buf, KRL_SECTION_EXPLICIT_KEY);
+                buffer_put_string(buf, buffer_ptr(&sect),
+                    buffer_len(&sect));
+        }
+        buffer_clear(&sect);
+        RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha1s) {
+                debug3("%s: hash len %u ", __func__, rb->len);
+                buffer_put_string(&sect, rb->blob, rb->len);
+        }
+        if (buffer_len(&sect) != 0) {
+                buffer_put_char(buf, KRL_SECTION_FINGERPRINT_SHA1);
+                buffer_put_string(buf, buffer_ptr(&sect),
+                    buffer_len(&sect));
+        }
+
+        for (i = 0; i < nsign_keys; i++) {
+                if (key_to_blob(sign_keys[i], &kblob, &klen) == 0)
+                        goto out;
+
+                debug3("%s: signature key len %u", __func__, klen);
+                buffer_put_char(buf, KRL_SECTION_SIGNATURE);
+                buffer_put_string(buf, kblob, klen);
+
+                if (key_sign(sign_keys[i], &sblob, &slen,
+                    buffer_ptr(buf), buffer_len(buf)) == -1)
+                        goto out;
+                debug3("%s: signature sig len %u", __func__, slen);
+                buffer_put_string(buf, sblob, slen);
+        }
+
+        r = 0;
+ out:
+        free(kblob);
+        free(sblob);
+        buffer_free(&sect);
+        return r;
+}
+
+static void
+format_timestamp(u_int64_t timestamp, char *ts, size_t nts)
+{
+        time_t t;
+        struct tm *tm;
+
+        t = timestamp;
+        tm = localtime(&t);
+        *ts = '\0';
+        strftime(ts, nts, "%Y%m%dT%H%M%S", tm);
+}
+
+static int
+parse_revoked_certs(Buffer *buf, struct ssh_krl *krl)
+{
+        int ret = -1, nbits;
+        u_char type, *blob;
+        u_int blen;
+        Buffer subsect;
+        u_int64_t serial, serial_lo, serial_hi;
+        BIGNUM *bitmap = NULL;
+        char *key_id = NULL;
+        Key *ca_key = NULL;
+
+        buffer_init(&subsect);
+
+        if ((blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL ||
+            buffer_get_string_ptr_ret(buf, NULL) == NULL) { /* reserved */
+                error("%s: buffer error", __func__);
+                goto out;
+        }
+        if ((ca_key = key_from_blob(blob, blen)) == NULL)
+                goto out;
+
+        while (buffer_len(buf) > 0) {
+                if (buffer_get_char_ret(&type, buf) != 0 ||
+                    (blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL) {
+                        error("%s: buffer error", __func__);
+                        goto out;
+                }
+                buffer_clear(&subsect);
+                buffer_append(&subsect, blob, blen);
+                debug3("%s: subsection type 0x%02x", __func__, type);
+                /* buffer_dump(&subsect); */
+
+                switch (type) {
+                case KRL_SECTION_CERT_SERIAL_LIST:
+                        while (buffer_len(&subsect) > 0) {
+                                if (buffer_get_int64_ret(&serial,
+                                    &subsect) != 0) {
+                                        error("%s: buffer error", __func__);
+                                        goto out;
+                                }
+                                if (ssh_krl_revoke_cert_by_serial(krl, ca_key,
+                                    serial) != 0) {
+                                        error("%s: update failed", __func__);
+                                        goto out;
+                                }
+                        }
+                        break;
+                case KRL_SECTION_CERT_SERIAL_RANGE:
+                        if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 ||
+                            buffer_get_int64_ret(&serial_hi, &subsect) != 0) {
+                                error("%s: buffer error", __func__);
+                                goto out;
+                        }
+                        if (ssh_krl_revoke_cert_by_serial_range(krl, ca_key,
+                            serial_lo, serial_hi) != 0) {
+                                error("%s: update failed", __func__);
+                                goto out;
+                        }
+                        break;
+                case KRL_SECTION_CERT_SERIAL_BITMAP:
+                        if ((bitmap = BN_new()) == NULL) {
+                                error("%s: BN_new", __func__);
+                                goto out;
+                        }
+                        if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 ||
+                            buffer_get_bignum2_ret(&subsect, bitmap) != 0) {
+                                error("%s: buffer error", __func__);
+                                goto out;
+                        }
+                        if ((nbits = BN_num_bits(bitmap)) < 0) {
+                                error("%s: bitmap bits < 0", __func__);
+                                goto out;
+                        }
+                        for (serial = 0; serial < (u_int)nbits; serial++) {
+                                if (serial > 0 && serial_lo + serial == 0) {
+                                        error("%s: bitmap wraps u64", __func__);
+                                        goto out;
+                                }
+                                if (!BN_is_bit_set(bitmap, serial))
+                                        continue;
+                                if (ssh_krl_revoke_cert_by_serial(krl, ca_key,
+                                    serial_lo + serial) != 0) {
+                                        error("%s: update failed", __func__);
+                                        goto out;
+                                }
+                        }
+                        BN_free(bitmap);
+                        bitmap = NULL;
+                        break;
+                case KRL_SECTION_CERT_KEY_ID:
+                        while (buffer_len(&subsect) > 0) {
+                                if ((key_id = buffer_get_cstring_ret(&subsect,
+                                    NULL)) == NULL) {
+                                        error("%s: buffer error", __func__);
+                                        goto out;
+                                }
+                                if (ssh_krl_revoke_cert_by_key_id(krl, ca_key,
+                                    key_id) != 0) {
+                                        error("%s: update failed", __func__);
+                                        goto out;
+                                }
+                                free(key_id);
+                                key_id = NULL;
+                        }
+                        break;
+                default:
+                        error("Unsupported KRL certificate section %u", type);
+                        goto out;
+                }
+                if (buffer_len(&subsect) > 0) {
+                        error("KRL certificate section contains unparsed data");
+                        goto out;
+                }
+        }
+
+        ret = 0;
+ out:
+        if (ca_key != NULL)
+                key_free(ca_key);
+        if (bitmap != NULL)
+                BN_free(bitmap);
+        free(key_id);
+        buffer_free(&subsect);
+        return ret;
+}
+
+
+/* Attempt to parse a KRL, checking its signature (if any) with sign_ca_keys. */
+int
+ssh_krl_from_blob(Buffer *buf, struct ssh_krl **krlp,
+    const Key **sign_ca_keys, u_int nsign_ca_keys)
+{
+        Buffer copy, sect;
+        struct ssh_krl *krl;
+        char timestamp[64];
+        int ret = -1, r, sig_seen;
+        Key *key = NULL, **ca_used = NULL;
+        u_char type, *blob;
+        u_int i, j, sig_off, sects_off, blen, format_version, nca_used = 0;
+
+        *krlp = NULL;
+        if (buffer_len(buf) < sizeof(KRL_MAGIC) - 1 ||
+            memcmp(buffer_ptr(buf), KRL_MAGIC, sizeof(KRL_MAGIC) - 1) != 0) {
+                debug3("%s: not a KRL", __func__);
+                /*
+                 * Return success but a NULL *krlp here to signal that the
+                 * file might be a simple list of keys.
+                 */
+                return 0;
+        }
+
+        /* Take a copy of the KRL buffer so we can verify its signature later */
+        buffer_init(&copy);
+        buffer_append(&copy, buffer_ptr(buf), buffer_len(buf));
+
+        buffer_init(&sect);
+        buffer_consume(&copy, sizeof(KRL_MAGIC) - 1);
+
+        if ((krl = ssh_krl_init()) == NULL) {
+                error("%s: alloc failed", __func__);
+                goto out;
+        }
+
+        if (buffer_get_int_ret(&format_version, &copy) != 0) {
+                error("%s: KRL truncated", __func__);
+                goto out;
+        }
+        if (format_version != KRL_FORMAT_VERSION) {
+                error("%s: KRL unsupported format version %u",
+                    __func__, format_version);
+                goto out;
+        }
+        if (buffer_get_int64_ret(&krl->krl_version, &copy) != 0 ||
+            buffer_get_int64_ret(&krl->generated_date, &copy) != 0 ||
+            buffer_get_int64_ret(&krl->flags, &copy) != 0 ||
+            buffer_get_string_ptr_ret(&copy, NULL) == NULL || /* reserved */
+            (krl->comment = buffer_get_cstring_ret(&copy, NULL)) == NULL) {
+                error("%s: buffer error", __func__);
+                goto out;
+        }
+
+        format_timestamp(krl->generated_date, timestamp, sizeof(timestamp));
+        debug("KRL version %llu generated at %s%s%s", krl->krl_version,
+            timestamp, *krl->comment ? ": " : "", krl->comment);
+
+        /*
+         * 1st pass: verify signatures, if any. This is done to avoid
+         * detailed parsing of data whose provenance is unverified.
+         */
+        sig_seen = 0;
+        sects_off = buffer_len(buf) - buffer_len(&copy);
+        while (buffer_len(&copy) > 0) {
+                if (buffer_get_char_ret(&type, &copy) != 0 ||
+                    (blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
+                        error("%s: buffer error", __func__);
+                        goto out;
+                }
+                debug3("%s: first pass, section 0x%02x", __func__, type);
+                if (type != KRL_SECTION_SIGNATURE) {
+                        if (sig_seen) {
+                                error("KRL contains non-signature section "
+                                    "after signature");
+                                goto out;
+                        }
+                        /* Not interested for now. */
+                        continue;
+                }
+                sig_seen = 1;
+                /* First string component is the signing key */
+                if ((key = key_from_blob(blob, blen)) == NULL) {
+                        error("%s: invalid signature key", __func__);
+                        goto out;
+                }
+                sig_off = buffer_len(buf) - buffer_len(&copy);
+                /* Second string component is the signature itself */
+                if ((blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
+                        error("%s: buffer error", __func__);
+                        goto out;
+                }
+                /* Check signature over entire KRL up to this point */
+                if (key_verify(key, blob, blen,
+                    buffer_ptr(buf), buffer_len(buf) - sig_off) == -1) {
+                        error("bad signaure on KRL");
+                        goto out;
+                }
+                /* Check if this key has already signed this KRL */
+                for (i = 0; i < nca_used; i++) {
+                        if (key_equal(ca_used[i], key)) {
+                                error("KRL signed more than once with "
+                                    "the same key");
+                                goto out;
+                        }
+                }
+                /* Record keys used to sign the KRL */
+                xrealloc(ca_used, nca_used + 1, sizeof(*ca_used));
+                ca_used[nca_used++] = key;
+                key = NULL;
+                break;
+        }
+
+        /*
+         * 2nd pass: parse and load the KRL, skipping the header to the point
+         * where the section start.
+         */
+        buffer_append(&copy, (u_char*)buffer_ptr(buf) + sects_off,
+            buffer_len(buf) - sects_off);
+        while (buffer_len(&copy) > 0) {
+                if (buffer_get_char_ret(&type, &copy) != 0 ||
+                    (blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
+                        error("%s: buffer error", __func__);
+                        goto out;
+                }
+                debug3("%s: second pass, section 0x%02x", __func__, type);
+                buffer_clear(&sect);
+                buffer_append(&sect, blob, blen);
+
+                switch (type) {
+                case KRL_SECTION_CERTIFICATES:
+                        if ((r = parse_revoked_certs(&sect, krl)) != 0)
+                                goto out;
+                        break;
+                case KRL_SECTION_EXPLICIT_KEY:
+                case KRL_SECTION_FINGERPRINT_SHA1:
+                        while (buffer_len(&sect) > 0) {
+                                if ((blob = buffer_get_string_ret(&sect,
+                                    &blen)) == NULL) {
+                                        error("%s: buffer error", __func__);
+                                        goto out;
+                                }
+                                if (type == KRL_SECTION_FINGERPRINT_SHA1 &&
+                                    blen != 20) {
+                                        error("%s: bad SHA1 length", __func__);
+                                        goto out;
+                                }
+                                if (revoke_blob(
+                                    type == KRL_SECTION_EXPLICIT_KEY ?
+                                    &krl->revoked_keys : &krl->revoked_sha1s,
+                                    blob, blen) != 0)
+                                        goto out; /* revoke_blob frees blob */
+                        }
+                        break;
+                case KRL_SECTION_SIGNATURE:
+                        /* Handled above, but still need to stay in synch */
+                        buffer_clear(&sect);
+                        if ((blob = buffer_get_string_ptr_ret(&sect,
+                            &blen)) == NULL) {
+                                error("%s: buffer error", __func__);
+                                goto out;
+                        }
+                        break;
+                default:
+                        error("Unsupported KRL section %u", type);
+                        goto out;
+                }
+                if (buffer_len(&sect) > 0) {
+                        error("KRL section contains unparsed data");
+                        goto out;
+                }
+        }
+
+        /* Check that the key(s) used to sign the KRL weren't revoked */
+        sig_seen = 0;
+        for (i = 0; i < nca_used; i++) {
+                if (ssh_krl_check_key(krl, ca_used[i]) == 0)
+                        sig_seen = 1;
+                else {
+                        key_free(ca_used[i]);
+                        ca_used[i] = NULL;
+                }
+        }
+        if (nca_used && !sig_seen) {
+                error("All keys used to sign KRL were revoked");
+                goto out;
+        }
+
+        /* If we have CA keys, then verify that one was used to sign the KRL */
+        if (sig_seen && nsign_ca_keys != 0) {
+                sig_seen = 0;
+                for (i = 0; !sig_seen && i < nsign_ca_keys; i++) {
+                        for (j = 0; j < nca_used; j++) {
+                                if (ca_used[j] == NULL)
+                                        continue;
+                                if (key_equal(ca_used[j], sign_ca_keys[i])) {
+                                        sig_seen = 1;
+                                        break;
+                                }
+                        }
+                }
+                if (!sig_seen) {
+                        error("KRL not signed with any trusted key");
+                        goto out;
+                }
+        }
+
+        *krlp = krl;
+        ret = 0;
+ out:
+        if (ret != 0)
+                ssh_krl_free(krl);
+        for (i = 0; i < nca_used; i++) {
+                if (ca_used[i] != NULL)
+                        key_free(ca_used[i]);
+        }
+        free(ca_used);
+        if (key != NULL)
+                key_free(key);
+        buffer_free(&copy);
+        buffer_free(&sect);
+        return ret;
+}
+
+/* Checks whether a given key/cert is revoked. Does not check its CA */
+static int
+is_key_revoked(struct ssh_krl *krl, const Key *key)
+{
+        struct revoked_blob rb, *erb;
+        struct revoked_serial rs, *ers;
+        struct revoked_key_id rki, *erki;
+        struct revoked_certs *rc;
+
+        /* Check explicitly revoked hashes first */
+        bzero(&rb, sizeof(rb));
+        if ((rb.blob = key_fingerprint_raw(key, SSH_FP_SHA1, &rb.len)) == NULL)
+                return -1;
+        erb = RB_FIND(revoked_blob_tree, &krl->revoked_sha1s, &rb);
+        free(rb.blob);
+        if (erb != NULL) {
+                debug("%s: revoked by key SHA1", __func__);
+                return -1;
+        }
+
+        /* Next, explicit keys */
+        bzero(&rb, sizeof(rb));
+        if (plain_key_blob(key, &rb.blob, &rb.len) != 0)
+                return -1;
+        erb = RB_FIND(revoked_blob_tree, &krl->revoked_keys, &rb);
+        free(rb.blob);
+        if (erb != NULL) {
+                debug("%s: revoked by explicit key", __func__);
+                return -1;
+        }
+
+        if (!key_is_cert(key))
+                return 0;
+
+        /* Check cert revocation */
+        if (revoked_certs_for_ca_key(krl, key->cert->signature_key,
+            &rc, 0) != 0)
+                return -1;
+        if (rc == NULL)
+                return 0; /* No entry for this CA */
+
+        /* Check revocation by cert key ID */
+        bzero(&rki, sizeof(rki));
+        rki.key_id = key->cert->key_id;
+        erki = RB_FIND(revoked_key_id_tree, &rc->revoked_key_ids, &rki);
+        if (erki != NULL) {
+                debug("%s: revoked by key ID", __func__);
+                return -1;
+        }
+
+        /* Legacy cert formats lack serial numbers */
+        if (key_cert_is_legacy(key))
+                return 0;
+
+        bzero(&rs, sizeof(rs));
+        rs.lo = rs.hi = key->cert->serial;
+        ers = RB_FIND(revoked_serial_tree, &rc->revoked_serials, &rs);
+        if (ers != NULL) {
+                KRL_DBG(("%s: %llu matched %llu:%llu", __func__,
+                    key->cert->serial, ers->lo, ers->hi));
+                debug("%s: revoked by serial", __func__);
+                return -1;
+        }
+        KRL_DBG(("%s: %llu no match", __func__, key->cert->serial));
+
+        return 0;
+}
+
+int
+ssh_krl_check_key(struct ssh_krl *krl, const Key *key)
+{
+        int r;
+
+        debug2("%s: checking key", __func__);
+        if ((r = is_key_revoked(krl, key)) != 0)
+                return r;
+        if (key_is_cert(key)) {
+                debug2("%s: checking CA key", __func__);
+                if ((r = is_key_revoked(krl, key->cert->signature_key)) != 0)
+                        return r;
+        }
+        debug3("%s: key okay", __func__);
+        return 0;
+}
+
+/* Returns 0 on success, -1 on error or key revoked, -2 if path is not a KRL */
+int
+ssh_krl_file_contains_key(const char *path, const Key *key)
+{
+        Buffer krlbuf;
+        struct ssh_krl *krl;
+        int revoked, fd;
+
+        if (path == NULL)
+                return 0;
+
+        if ((fd = open(path, O_RDONLY)) == -1) {
+                error("open %s: %s", path, strerror(errno));
+                error("Revoked keys file not accessible - refusing public key "
+                    "authentication");
+                return -1;
+        }
+        buffer_init(&krlbuf);
+        if (!key_load_file(fd, path, &krlbuf)) {
+                close(fd);
+                buffer_free(&krlbuf);
+                error("Revoked keys file not readable - refusing public key "
+                    "authentication");
+                return -1;
+        }
+        close(fd);
+        if (ssh_krl_from_blob(&krlbuf, &krl, NULL, 0) != 0) {
+                buffer_free(&krlbuf);
+                error("Invalid KRL, refusing public key "
+                    "authentication");
+                return -1;
+        }
+        buffer_free(&krlbuf);
+        if (krl == NULL) {
+                debug3("%s: %s is not a KRL file", __func__, path);
+                return -2;
+        }
+        debug2("%s: checking KRL %s", __func__, path);
+        revoked = ssh_krl_check_key(krl, key) != 0;
+        ssh_krl_free(krl);
+        return revoked ? -1 : 0;
+}