X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/e04c2d50fd96f3f31bc96851c55c6efecc10469c..15e8239f47dbd30b4da82dfedf983e07bc2f4122:/server/keymgmt.c

diff --git a/server/keymgmt.c b/server/keymgmt.c
index 422b01fe..17325dce 100644
--- a/server/keymgmt.c
+++ b/server/keymgmt.c
@@ -1,6 +1,4 @@
 /* -*-c-*-
- *
- * $Id$
  *
  * Key loading and storing
  *
@@ -30,213 +28,278 @@
 
 #include "tripe.h"
 
-/*----- Global variables --------------------------------------------------*/
-
-group *gg;
-mp *kpriv;
-ge *kpub;
-algswitch algs;
-size_t indexsz;
-
-/*----- Static variables --------------------------------------------------*/
-
-static key_file *kf_pub;
-static const char *kr_priv, *kr_pub, *tag_priv;
-static fwatch w_priv, w_pub;
-
 /*----- Key groups --------------------------------------------------------*/
 
+/* The key-loading functions here must fill in the kdata slot @g@ and
+ * either @kpriv@ or @kpub@ as appropriate.  The caller will take care of
+ * determining @kpub@ given a private key, and of ensuring that @kpriv@ is
+ * null for a public key.
+ */
+
 typedef struct kgops {
   const char *ty;
-  const char *(*loadpriv)(key_data *, group **, mp **, dstr *);
-  const char *(*loadpub)(key_data *, group **, ge **, dstr *);
+  int (*loadpriv)(key_data *, kdata *, dstr *, dstr *);
+  int (*loadpub)(key_data *, kdata *, dstr *, dstr *);
 } kgops;
 
-/* --- Diffie-Hellman --- */
-
-static const char *kgdh_priv(key_data *kd, group **g, mp **x, dstr *t)
-{
-  key_packstruct kps[DH_PRIVFETCHSZ];
-  key_packdef *kp;
-  dh_priv dp;
-  const char *e;
-  int rc;
-
-  kp = key_fetchinit(dh_privfetch, kps, &dp);
-  if ((rc = key_unpack(kp, kd, t)) != 0) {
-    e = key_strerror(rc);
-    goto done;
-  }
-  *g = group_prime(&dp.dp);
-  *x = MP_COPY(dp.x);
-  e = 0;
-done:
-  key_fetchdone(kp);
-  return (e);
-}
-
-static const char *kgdh_pub(key_data *kd, group **g, ge **p, dstr *t)
-{
-  key_packstruct kps[DH_PUBFETCHSZ];
-  key_packdef *kp;
-  dh_pub dp;
-  const char *e;
-  int rc;
-
-  kp = key_fetchinit(dh_pubfetch, kps, &dp);
-  if ((rc = key_unpack(kp, kd, t)) != 0) {
-    e = key_strerror(rc);
-    goto done;
-  }
-  *g = group_prime(&dp.dp);
-  *p = G_CREATE(*g);
-  if (G_FROMINT(*g, *p, dp.y)) {
-    e = "bad public value";
-    goto done;
-  }
-  e = 0;
-done:
-  key_fetchdone(kp);
-  return (e);
-}
-
-static const kgops kgdh_ops = { "tripe-dh", kgdh_priv, kgdh_pub };
-
-/* --- Elliptic curve --- */
-
-static const char *kgec_priv(key_data *kd, group **g, mp **x, dstr *t)
-{
-  key_packstruct kps[EC_PRIVFETCHSZ];
-  key_packdef *kp;
-  ec_priv ep;
-  ec_info ei;
-  const char *e;
-  int rc;
+/* --- @KLOAD@ --- *
+ *
+ * Arguments:	@ty@, @TY@ = key type name (lower- and upper-case)
+ *		@which@, @WHICH@ = `pub' or `priv' (and upper-case)
+ *		@setgroup@ = code to initialize @kd->g@
+ *		@setpriv@ = code to initialize @kd->kpriv@
+ *		@setpub@ = code to initialize @kd->kpub@
+ *
+ * Use:		Generates the body of one of the (rather tedious) key loading
+ *		functions.  See the description of @KEYTYPES@ below for the
+ *		details.
+ */
 
-  kp = key_fetchinit(ec_privfetch, kps, &ep);
-  if ((rc = key_unpack(kp, kd, t)) != 0) {
-    e = key_strerror(rc);
-    goto done;
-  }
-  if ((e = ec_getinfo(&ei, ep.cstr)) != 0)
-    goto done;
-  *g = group_ec(&ei);
-  *x = MP_COPY(ep.x);
-  e = 0;
-done:
-  key_fetchdone(kp);
-  return (e);
+#define KLOAD(ty, TY, which, WHICH, setgroup, setpriv, setpub)		\
+static int kg##ty##_##which(key_data *d, kdata *kd, dstr *t, dstr *e)	\
+{									\
+  key_packstruct kps[TY##_##WHICH##FETCHSZ];				\
+  key_packdef *kp;							\
+  ty##_##which p;							\
+  int rc;								\
+									\
+  /* --- Initialize things we've not set up yet --- */			\
+									\
+  kd->g = 0; kd->kpub = 0;						\
+									\
+  /* --- Unpack the key --- */						\
+									\
+  kp = key_fetchinit(ty##_##which##fetch, kps, &p);			\
+  if ((rc = key_unpack(kp, d, t)) != 0) {				\
+    a_format(e, "unpack-failed", "%s", key_strerror(rc), A_END);	\
+    goto fail;								\
+  }									\
+									\
+  /* --- Extract the pieces of the key --- */				\
+									\
+  setgroup;								\
+  setpriv;								\
+  kd->kpub = G_CREATE(kd->g);						\
+  setpub;								\
+									\
+  /* --- We win --- */							\
+									\
+  rc = 0;								\
+  goto done;								\
+									\
+fail:									\
+  if (kd->kpub) G_DESTROY(kd->g, kd->kpub);				\
+  if (kd->g) G_DESTROYGROUP(kd->g);					\
+  rc = -1;								\
+									\
+done:									\
+  key_fetchdone(kp);							\
+  return (rc);								\
 }
 
-static const char *kgec_pub(key_data *kd, group **g, ge **p, dstr *t)
-{
-  key_packstruct kps[EC_PUBFETCHSZ];
-  key_packdef *kp;
-  ec_pub ep;
-  ec_info ei;
-  const char *e;
-  int rc;
+/* --- @KEYTYPES@ --- *
+ *
+ * A list of the various key types, and how to unpack them.  Each entry in
+ * the list has the form
+ *
+ *	_(ty, TY, setgroup, setpriv, setpub)
+ *
+ * The @ty@ and @TY@ are lower- and upper-case versions of the key type name,
+ * and there should be @key_fetchdef@s called @ty_{priv,pub}fetch@.
+ *
+ * The @setgroup@, @setpriv@ and @setpub@ items are code fragments which are
+ * passed to @KLOAD@ to build appropriate key-loading methods.  By the time
+ * these code fragments are run, the key has been unpacked from the incoming
+ * key data using @ty_whichfetch@ into a @ty_which@ structure named @p@.
+ * They can report errors by writing an appropriate token sequence to @e@ and
+ * jumping to @fail@.
+ */
 
-  kp = key_fetchinit(ec_pubfetch, kps, &ep);
-  if ((rc = key_unpack(kp, kd, t)) != 0) {
-    e = key_strerror(rc);
-    goto done;
-  }
-  if ((e = ec_getinfo(&ei, ep.cstr)) != 0)
-    goto done;
-  *g = group_ec(&ei);
-  *p = G_CREATE(*g);
-  if (G_FROMEC(*g, *p, &ep.p)) {
-    e = "bad public point";
-    goto done;
-  }
-  e = 0;
-done:
-  key_fetchdone(kp);
-  return (e);
-}
+#define KEYTYPES(_)							\
+									\
+  /* --- Diffie-Hellman --- */						\
+									\
+  _(dh, DH,								\
+    { kd->g = group_prime(&p.dp); },					\
+    { kd->kpriv = MP_COPY(p.x); },					\
+    { if (G_FROMINT(kd->g, kd->kpub, p.y)) {				\
+	a_format(e, "bad-public-vector", A_END);			\
+	goto fail;							\
+      }									\
+    })									\
+									\
+  /* --- Elliptic curves --- */						\
+									\
+  _(ec, EC,								\
+    { ec_info ei; const char *err;					\
+      if ((err = ec_getinfo(&ei, p.cstr)) != 0) {			\
+	a_format(e, "decode-failed", "%s", err, A_END);			\
+	goto fail;							\
+      }									\
+      kd->g = group_ec(&ei);						\
+    },									\
+    { kd->kpriv = MP_COPY(p.x); },					\
+    { if (G_FROMEC(kd->g, kd->kpub, &p.p)) {				\
+	a_format(e, "bad-public-vector", A_END);			\
+	goto fail;							\
+      }									\
+    })
 
-static const kgops kgec_ops = { "tripe-ec", kgec_priv, kgec_pub };
+#define KEYTYPE_DEF(ty, TY, setgroup, setpriv, setpub)			\
+  KLOAD(ty, TY, priv, PRIV, setgroup, setpriv,				\
+	{ G_EXP(kd->g, kd->kpub, kd->g->g, kd->kpriv); })		\
+  KLOAD(ty, TY, pub, PUB, setgroup, { }, setpub)			\
+  static const kgops kg##ty##_ops = { #ty, kg##ty##_priv, kg##ty##_pub };
+KEYTYPES(KEYTYPE_DEF)
 
 /* --- Table of supported key types --- */
 
-static const kgops *kgtab[] = { &kgdh_ops, &kgec_ops, 0 };
+static const kgops *kgtab[] = {
+#define KEYTYPE_ENTRY(ty, TY, setgroup, setpriv, setpub) &kg##ty##_ops,
+  KEYTYPES(KEYTYPE_ENTRY)
+#undef KEYTYPE_ENTRY
+  0
+};
 
 /*----- Algswitch stuff ---------------------------------------------------*/
 
 /* --- @algs_get@ --- *
  *
  * Arguments:	@algswitch *a@ = where to put the algorithms
- *		@key_file *kf@ = key file (for some stupid reason)
+ *		@dstr *e@ = where to write errror tokens
+ *		@key_file *kf@ = key file
  *		@key *k@ = key to inspect
  *
- * Returns:	Null if OK, or an error message.
+ * Returns:	Zero if OK; nonzero on error.
  *
  * Use:		Extracts an algorithm choice from a key.
  */
 
-static const char *algs_get(algswitch *a, key_file *kf, key *k)
+static int algs_get(algswitch *a, dstr *e, key_file *kf, key *k)
 {
   const char *p;
-  char *q;
-  dstr d = DSTR_INIT;
-  const char *e;
+  const bulkcrypto *bulk;
+  char *q, *qq;
+  dstr d = DSTR_INIT, dd = DSTR_INIT;
+  int rc = -1;
 
-#define FAIL(msg) do { e = msg; goto done; } while (0)
+  /* --- Hash function --- */
 
-  if ((p = key_getattr(kf, k, "cipher")) == 0)
-    p = "blowfish-cbc";
-  if ((a->c = gcipher_byname(p)) == 0)
-    FAIL("unknown-cipher");
+  if ((p = key_getattr(kf, k, "hash")) == 0) p = "rmd160";
+  if ((a->h = ghash_byname(p)) == 0) {
+    a_format(e, "unknown-hash", "%s", p, A_END);
+    goto done;
+  }
 
-  if ((p = key_getattr(kf, k, "hash")) == 0)
-    p = "rmd160";
-  if ((a->h = ghash_byname(p)) == 0)
-    FAIL("unknown-hash");
+  /* --- Symmetric encryption for key derivation --- */
 
   if ((p = key_getattr(kf, k, "mgf")) == 0) {
     dstr_reset(&d);
     dstr_putf(&d, "%s-mgf", a->h->name);
     p = d.buf;
   }
-  if ((a->mgf = gcipher_byname(p)) == 0)
-    FAIL("unknown-mgf-cipher");
+  if ((a->mgf = gcipher_byname(p)) == 0) {
+    a_format(e, "unknown-mgf-cipher", "%s", p, A_END);
+    goto done;
+  }
+
+  /* --- Bulk crypto transform --- */
+
+  if ((p = key_getattr(kf, k, "bulk")) == 0) p = "v0";
+  for (bulk = bulktab; bulk->name && strcmp(p, bulk->name) != 0; bulk++);
+  if (!bulk->name) {
+    a_format(e, "unknown-bulk-transform", "%s", p, A_END);
+    goto done;
+  }
+  a->bulk = bulk;
+
+  /* --- Symmetric encryption for bulk data --- */
 
-  if ((p = key_getattr(kf, k, "mac")) != 0) {
+  if (!(a->bulk->prim & BCP_CIPHER))
+    a->c = 0;
+  else {
+    if ((p = key_getattr(kf, k, "cipher")) == 0) p = "blowfish-cbc";
+    if ((a->c = gcipher_byname(p)) == 0) {
+      a_format(e, "unknown-cipher", "%s", p, A_END);
+      goto done;
+    }
+  }
+
+  /* --- Block cipher for miscellaneous use --- */
+
+  if (!(a->bulk->prim & BCP_BLKC))
+    a->b = 0;
+  else {
+    if ((p = key_getattr(kf, k, "blkc")) == 0) {
+      dstr_reset(&dd);
+      dstr_puts(&dd, a->c ? a->c->name : "rijndael-");
+      if ((q = strrchr(dd.buf, '-')) != 0) *q = 0;
+      p = dd.buf;
+    }
     dstr_reset(&d);
-    dstr_puts(&d, p);
-    if ((q = strchr(d.buf, '/')) != 0)
-      *q++ = 0;
-    if ((a->m = gmac_byname(d.buf)) == 0)
-      FAIL("unknown-mac");
-    if (!q)
-      a->tagsz = a->m->hashsz;
-    else {
-      unsigned long n = strtoul(q, &q, 0);
-      if (*q) FAIL("bad-tag-length-string");
-      if (n%8 || n > ~(size_t)0) FAIL("bad-tag-length");
-      a->tagsz = n/8;
+    dstr_putf(&d, "%s-ecb", p);
+    if ((a->b = gcipher_byname(d.buf)) == 0) {
+      a_format(e, "unknown-blkc", "%s", p, A_END);
+      goto done;
     }
+  }
+
+  /* --- Message authentication for bulk data --- */
+
+  if (!(a->bulk->prim & BCP_MAC)) {
+    a->m = 0;
+    a->tagsz = 0;
   } else {
-    dstr_reset(&d);
-    dstr_putf(&d, "%s-hmac", a->h->name);
-    if ((a->m = gmac_byname(d.buf)) == 0)
-      FAIL("no-hmac-for-hash");
-    a->tagsz = a->h->hashsz/2;
+    if ((p = key_getattr(kf, k, "mac")) != 0) {
+      dstr_reset(&d);
+      dstr_puts(&d, p);
+      if ((q = strchr(d.buf, '/')) != 0)
+	*q++ = 0;
+      if ((a->m = gmac_byname(d.buf)) == 0) {
+	a_format(e, "unknown-mac", "%s", d.buf, A_END);
+	goto done;
+      }
+      if (!q)
+	a->tagsz = a->m->hashsz;
+      else {
+	unsigned long n = strtoul(q, &qq, 0);
+	if (*qq)  {
+	  a_format(e, "bad-tag-length-string", "%s", q, A_END);
+	  goto done;
+	}
+	if (n%8 || n/8 > a->m->hashsz) {
+	  a_format(e, "bad-tag-length", "%lu", n, A_END);
+	  goto done;
+	}
+	a->tagsz = n/8;
+      }
+    } else {
+      dstr_reset(&d);
+      dstr_putf(&d, "%s-hmac", a->h->name);
+      if ((a->m = gmac_byname(d.buf)) == 0) {
+	a_format(e, "no-hmac-for-hash", "%s", a->h->name, A_END);
+	goto done;
+      }
+      a->tagsz = a->h->hashsz/2;
+    }
   }
 
-  e = 0;
+  /* --- All done --- */
+
+  rc = 0;
 done:
   dstr_destroy(&d);
-  return (e);
+  dstr_destroy(&dd);
+  return (rc);
 }
 
 /* --- @algs_check@ --- *
  *
  * Arguments:	@algswitch *a@ = a choice of algorithms
+ *		@dstr *e@ = where to write error tokens
  *		@const group *g@ = the group we're working in
  *
- * Returns:	Null if OK, or an error message.
+ * Returns:	Zero if OK; nonzero on error.
  *
  * Use:		Checks an algorithm choice for sensibleness.  This also
  *		derives some useful information from the choices, and you
@@ -244,58 +307,165 @@ done:
  *		for use by @keyset@ functions.
  */
 
-static const char *algs_check(algswitch *a, const group *g)
+static int algs_check(algswitch *a, dstr *e, const group *g)
 {
+  /* --- Check the bulk crypto transform --- */
+
+  if (a->bulk->check(a, e)) return (-1);
+
   /* --- Derive the key sizes --- *
    *
    * Must ensure that we have non-empty keys.  This isn't ideal, but it
-   * provides a handy sanity check.
+   * provides a handy sanity check.  Also must be based on a 64- or 128-bit
+   * block cipher or we can't do the data expiry properly.
    */
 
   a->hashsz = a->h->hashsz;
-  if ((a->cksz = keysz(a->hashsz, a->c->keysz)) == 0)
-    return ("no key size found for cipher");
-  if ((a->mksz = keysz(a->hashsz, a->m->keysz)) == 0)
-    return ("no key size found for MAC");
+  if (a->c && (a->cksz = keysz(a->hashsz, a->c->keysz)) == 0) {
+    a_format(e, "cipher", "%s", a->c->name,
+	     "no-key-size", "%lu", (unsigned long)a->hashsz,
+	     A_END);
+    return (-1);
+  }
+  if (a->m && (a->mksz = keysz(a->hashsz, a->m->keysz)) == 0) {
+    a_format(e, "mac", "%s", a->m->name,
+	     "no-key-size", "%lu", (unsigned long)a->hashsz,
+	     A_END);
+    return (-1);
+  }
+  if (a->b && (a->bksz = keysz(a->hashsz, a->b->keysz)) == 0) {
+    a_format(e, "blkc", "%.*s", strlen(a->b->name) - 4, a->b->name,
+	     "no-key-size", "%lu", (unsigned long)a->hashsz,
+	     A_END);
+    return (-1);
+  }
 
-  /* --- Ensure that the tag size is sane --- */
+  /* --- Derive the data limit --- */
 
-  if (a->tagsz > a->m->hashsz) return ("tag length too large");
+  if (a->c && a->c->blksz < 16) a->expsz = MEG(64);
+  else a->expsz = MEG(2048);
 
   /* --- Ensure the MGF accepts hashes as keys --- */
 
-  if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz)
-    return ("MGF not suitable -- restrictive key schedule");
+  if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz) {
+    a_format(e, "mgf", "%s", a->mgf->name,
+	     "restrictive-key-schedule",
+	     A_END);
+    return (-1);
+  }
 
   /* --- All ship-shape and Bristol-fashion --- */
 
   return (0);
 }
 
-/* --- @algs_samep@ --- *
+/* --- @km_samealgsp@ --- *
  *
- * Arguments:	@const algswitch *a, *aa@ = two algorithm selections
+ * Arguments:	@const kdata *kdx, *kdy@ = two key data objects
  *
- * Returns:	Nonzero if the two selections are the same.
+ * Returns:	Nonzero if their two algorithm selections are the same.
  *
  * Use:		Checks sameness of algorithm selections: used to ensure that
  *		peers are using sensible algorithms.
  */
 
-static int algs_samep(const algswitch *a, const algswitch *aa)
+int km_samealgsp(const kdata *kdx, const kdata *kdy)
 {
-  return (a->c == aa->c && a->mgf == aa->mgf && a->h == aa->h &&
+  const algswitch *a = &kdx->algs, *aa = &kdy->algs;
+
+  return (group_samep(kdx->g, kdy->g) &&
+	  a->c == aa->c && a->b == aa->b &&
+	  a->mgf == aa->mgf && a->h == aa->h &&
 	  a->m == aa->m && a->tagsz == aa->tagsz);
 }
 
-/*----- Main code ---------------------------------------------------------*/
+/*----- Key data and key nodes --------------------------------------------*/
+
+typedef struct keyhalf {
+  const char *kind;
+  int (*load)(const kgops *, key_data *, kdata *, dstr *, dstr *);
+  const char *kr;
+  key_file *kf;
+  fwatch w;
+  sym_table tab;
+} keyhalf;
+
+/* --- @kh_loadpub@, @kh_loadpriv@ --- *
+ *
+ * Arguments:	@const kgops *ko@ = key-group operations for key type
+ *		@key_data *d@ = key data object as stored in keyring
+ *		@kdata *kd@ = our key-data object to fill in
+ *		@dstr *t@ = the key tag name
+ *		@dstr *e@ = a string to write error tokens to
+ *
+ * Returns:	Zero on success, @-1@ on error.
+ *
+ * Use:		These functions handle the main difference between public and
+ *		private key halves.  They are responsible for setting @g@,
+ *		@kpriv@ and @kpub@ appropriately in all keys, handling the
+ *		mismatch between the largely half-indifferent calling code
+ *		and the group-specific loading functions.
+ *
+ *		The function @kh_loadpriv@ is also responsible for checking
+ *		the group for goodness.  We don't bother checking public
+ *		keys, because each public key we actually end up using must
+ *		share a group with a private key which we'll already have
+ *		checked.
+ */
+
+static int kh_loadpub(const kgops *ko, key_data *d, kdata *kd,
+		      dstr *t, dstr *e)
+{
+  int rc;
+
+  if ((rc = ko->loadpub(d, kd, t, e)) != 0)
+    goto fail_0;
+  if (group_check(kd->g, kd->kpub)) {
+    a_format(e, "bad-public-group-element", A_END);
+    goto fail_1;
+  }
+  kd->kpriv = 0;
+  return (0);
+
+fail_1:
+  G_DESTROY(kd->g, kd->kpub);
+  G_DESTROYGROUP(kd->g);
+fail_0:
+  return (-1);
+}
+
+static int kh_loadpriv(const kgops *ko, key_data *d, kdata *kd,
+		       dstr *t, dstr *e)
+{
+  int rc;
+  const char *err;
+
+  if ((rc = ko->loadpriv(d, kd, t, e)) != 0)
+    goto fail_0;
+  if ((err = G_CHECK(kd->g, &rand_global)) != 0) {
+    a_format(e, "bad-group", "%s", err, A_END);
+    goto fail_1;
+  }
+  return (0);
+
+fail_1:
+  mp_drop(kd->kpriv);
+  G_DESTROY(kd->g, kd->kpub);
+  G_DESTROYGROUP(kd->g);
+fail_0:
+  return (-1);
+}
+
+static struct keyhalf
+  priv = { "private", kh_loadpriv },
+  pub = { "public", kh_loadpub };
 
 /* --- @keymoan@ --- *
  *
  * Arguments:	@const char *file@ = name of the file
  *		@int line@ = line number in file
  *		@const char *msg@ = error message
- *		@void *p@ = argument pointer
+ *		@void *p@ = argument pointer (indicates which keyring)
  *
  * Returns:	---
  *
@@ -304,234 +474,316 @@ static int algs_samep(const algswitch *a, const algswitch *aa)
 
 static void keymoan(const char *file, int line, const char *msg, void *p)
 {
-  a_warn("KEYMGMT",
-	 "key-file-error",
-	 "%s:%i", file, line,
-	 "%s", msg,
-	 A_END);
+  keyhalf *kh = p;
+
+  if (!line) {
+    a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file,
+	   "io-error", "?ERRNO", A_END);
+  } else {
+    a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file, "line", "%d", line,
+	   "%s", msg, A_END);
+  }
 }
 
-/* --- @loadpriv@ --- *
+/* --- @kh_reopen@ --- *
  *
- * Arguments:	@dstr *d@ = string to write errors in
+ * Arguments:	@keyhalf *kh@ = pointer to keyhalf structure
  *
- * Returns:	Zero if OK, nonzero on error.
+ * Returns:	Zero on success, @-1@ on error.
  *
- * Use:		Loads the private key from its keyfile.
+ * Use:		Reopens the key file for the appropriate key half.  If this
+ *		fails, everything is left as it was; if it succeeds, then the
+ *		old file is closed (if it was non-null) and the new one put
+ *		in its place.
  */
 
-static int loadpriv(dstr *d)
+static int kh_reopen(keyhalf *kh)
 {
-  key_file kf;
-  key *k;
-  key_data **kd;
-  dstr t = DSTR_INIT;
-  group *g = 0;
-  mp *x = 0;
-  int rc = -1;
-  const kgops **ko;
-  const char *e;
-  algswitch a;
-
-  /* --- Open the private key file --- */
-
-  if (key_open(&kf, kr_priv, KOPEN_READ, keymoan, 0)) {
-    dstr_putf(d, "error reading private keyring `%s': %s",
-	      kr_priv, strerror(errno));
-    goto done_0;
-  }
-
-  /* --- Find the private key --- */
+  key_file *kf = CREATE(key_file);
 
-  if (key_qtag(&kf, tag_priv, &t, &k, &kd)) {
-    dstr_putf(d, "private key `%s' not found in keyring `%s'",
-	      tag_priv, kr_priv);
-    goto done_1;
+  if (key_open(kf, kh->kr, KOPEN_READ, keymoan, kh)) {
+    a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
+	   "io-error", "?ERRNO", A_END);
+    DESTROY(kf);
+    return (-1);
+  } else {
+    if (kh->kf) {
+      key_close(kh->kf);
+      DESTROY(kh->kf);
+    }
+    kh->kf = kf;
+    return (0);
   }
+}
 
-  /* --- Look up the key type in the table --- */
-
-  for (ko = kgtab; *ko; ko++) {
-    if (strcmp((*ko)->ty, k->type) == 0)
-      goto tymatch;
-  }
-  dstr_putf(d, "private key `%s' has unknown type `%s'", t.buf, k->type);
-  goto done_1;
-tymatch:;
+/* --- @kh_init@ --- *
+ *
+ * Arguments:	@keyhalf *kh@ = pointer to keyhalf structure to set up
+ *		@const char *kr@ = name of the keyring file
+ *
+ * Returns:	---
+ *
+ * Use:		Initialize a keyhalf structure, maintaining the private or
+ *		public keys.  Intended to be called during initialization:
+ *		exits if there's some kind of problem.
+ */
 
-  /* --- Load the key --- */
+static void kh_init(keyhalf *kh, const char *kr)
+{
+  kh->kr = kr;
+  fwatch_init(&kh->w, kr);
+  sym_create(&kh->tab);
+  kh->kf = 0;
 
-  if ((e = (*ko)->loadpriv(*kd, &g, &x, &t)) != 0) {
-    dstr_putf(d, "error reading private key `%s': %s", t.buf, e);
-    goto done_1;
-  }
+  if (kh_reopen(kh))
+    die(EXIT_FAILURE, "failed to load %s keyring `%s'", kh->kind, kr);
+}
 
-  /* --- Check that the key is sensible --- */
+/* --- @kh_load@ --- *
+ *
+ * Arguments:	@keyhalf *kh@ = pointer to keyhalf
+ *		@const char *tag@ = key tag to be loaded
+ *		@int complainp@ = whether to complain about missing keys
+ *
+ * Returns:	Pointer to a @kdata@ structure if successful, or null on
+ *		failure.
+ *
+ * Use:		Attempts to load a key from the current key file.  This
+ *		function always reads data from the file: it's used when
+ *		there's a cache miss from @kh_find@, and when refreshing the
+ *		known keys in @kh_refresh@.  The returned kdata has a
+ *		reference count of exactly 1, and has no home knode.
+ */
 
-  if ((e = G_CHECK(g, &rand_global)) != 0) {
-    dstr_putf(d, "bad group in private key `%s': %s", t.buf, e);
-    goto done_1;
-  }
+static kdata *kh_load(keyhalf *kh, const char *tag, int complainp)
+{
+  dstr t = DSTR_INIT;
+  dstr e = DSTR_INIT;
+  key *k;
+  key_data **d;
+  kdata *kd;
+  const char *ty;
+  const kgops **ko;
 
-  /* --- Collect the algorithms --- */
+  /* --- Find the key and grab its tag --- */
 
-  if ((e = algs_get(&a, &kf, k)) != 0 ||
-      (e = algs_check(&a, g)) != 0) {
-    dstr_putf(d, "bad symmetric algorithm selection in private key `%s': %s",
-	      t.buf, e);
-    goto done_1;
+  if (key_qtag(kh->kf, tag, &t, &k, &d)) {
+    if (complainp) {
+      a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
+	     "key-not-found", "%s", tag, A_END);
+    }
+    goto fail_0;
   }
 
-  /* --- Good, we're happy --- *
+  /* --- Find the key's group type and the appropriate operations --- *
    *
-   * Dodginess!	 We change the group over here, but don't free any old group
-   * elements.  This assumes that the new group is basically the same as the
-   * old one, and will happily adopt the existing elements.  If it isn't,
-   * then we lose badly.  Check this, then.
+   * There are several places to look for the key type.  The most obvious is
+   * the `kx-group' key attribute.  But there's also the key type itself, for
+   * compatibility reasons.
    */
 
-  if (gg) {
-    if (!group_samep(g, gg)) {
-      dstr_putf(d, "private key `%s' has different group", t.buf);
-      goto done_1;
-    }
-    G_DESTROYGROUP(gg);
+  ty = key_getattr(kh->kf, k, "kx-group");
+  if (!ty && strncmp(k->type, "tripe-", 6) == 0) ty = k->type + 6;
+  if (!ty) ty = "dh";
+
+  for (ko = kgtab; *ko; ko++)
+    if (strcmp((*ko)->ty, ty) == 0) goto foundko;
+  a_warn("KEYMGMT", "%s-keyring", kh->kind,
+	 "%s", kh->kr, "key", "%s", t.buf,
+	 "unknown-group-type", "%s", ty, A_END);
+  goto fail_0;
+
+foundko:
+  kd = CREATE(kdata);
+  if (kh->load(*ko, *d, kd, &t, &e)) {
+    a_warn("KEYMGMT", "%s-keyring", kh->kind,
+	   "%s", kh->kr, "key" "%s", t.buf,
+	   "*%s", e.buf, A_END);
+    goto fail_1;
   }
-  if (kpriv)
-    mp_drop(kpriv);
 
-  if (kpub)
-    G_DESTROY(g, kpub);
-  kpub = G_CREATE(g);
-  G_EXP(g, kpub, g->g, x);
-  indexsz = mp_octets(g->r);
+  if (algs_get(&kd->algs, &e, kh->kf, k) ||
+      (kd->kpriv && algs_check(&kd->algs, &e, kd->g))) {
+    a_warn("KEYMGMT", "%s-keyring", kh->kind,
+	   "%s", kh->kr, "key", "%s", t.buf,
+	   "*%s", e.buf, A_END);
+    goto fail_2;
+  }
 
-  /* --- Dump out the group --- */
+  kd->tag = xstrdup(t.buf);
+  kd->indexsz = mp_octets(kd->g->r);
+  kd->ref = 1;
+  kd->kn = 0;
+  kd->t_exp = k->exp;
 
   IF_TRACING(T_KEYMGMT, {
-    trace(T_KEYMGMT, "keymgmt: extracted private key `%s'", t.buf);
+    trace(T_KEYMGMT, "keymgmt: loaded %s key `%s'", kh->kind, t.buf);
     IF_TRACING(T_CRYPTO, {
-      trace(T_CRYPTO, "crypto: r = %s", mpstr(g->r));
-      trace(T_CRYPTO, "crypto: h = %s", mpstr(g->h));
-      trace(T_CRYPTO, "crypto: x = %s", mpstr(x));
-      trace(T_CRYPTO, "crypto: cipher = %s", a.c->name);
-      trace(T_CRYPTO, "crypto: mgf = %s", a.mgf->name);
-      trace(T_CRYPTO, "crypto: hash = %s", a.h->name);
+      trace(T_CRYPTO, "crypto: r = %s", mpstr(kd->g->r));
+      trace(T_CRYPTO, "crypto: h = %s", mpstr(kd->g->h));
+      if (kd->kpriv)
+	trace(T_CRYPTO, "crypto: x = %s", mpstr(kd->kpriv));
+      trace(T_CRYPTO, "crypto: cipher = %s", kd->algs.c->name);
+      trace(T_CRYPTO, "crypto: mgf = %s", kd->algs.mgf->name);
+      trace(T_CRYPTO, "crypto: hash = %s", kd->algs.h->name);
       trace(T_CRYPTO, "crypto: mac = %s/%lu",
-	    a.m->name, (unsigned long)a.tagsz * 8);
+	    kd->algs.m->name, (unsigned long)kd->algs.tagsz * 8);
     })
   })
 
-  /* --- Success! --- */
-
-  gg = g; g = 0;
-  algs = a;
-  kpriv = x; x = 0;
-  rc = 0;
-
-  /* --- Tidy up --- */
+  goto done;
 
-done_1:
-  key_close(&kf);
-done_0:
+fail_2:
+  if (kd->kpriv) mp_drop(kd->kpriv);
+  G_DESTROY(kd->g, kd->kpub);
+  G_DESTROYGROUP(kd->g);
+fail_1:
+  DESTROY(kd);
+fail_0:
+  kd = 0;
+done:
   dstr_destroy(&t);
-  if (x) mp_drop(x);
-  if (g) G_DESTROYGROUP(g);
-  return (rc);
+  dstr_destroy(&e);
+  return (kd);
 }
 
-/* --- @loadpub@ --- *
+/* --- @kh_find@ --- *
  *
- * Arguments:	@dstr *d@ = string to write errors to
+ * Arguments:	@keyhalf *kh@ = pointer to the keyhalf
+ *		@const char *tag@ = key to be obtained
+ *		@int complainp@ = whether to complain about missing keys
  *
- * Returns:	Zero if OK, nonzero on error.
+ * Returns:	A pointer to the kdata, or null on error.
  *
- * Use:		Reloads the public keyring.
+ * Use:		Obtains kdata, maybe from the cache.  This won't update a
+ *		stale cache entry, though @kh_refresh@ ought to have done
+ *		that already.  The returned kdata object may be shared with
+ *		other users.  (One of this function's responsibilities, over
+ *		@kh_load@, is to set the home knode of a freshly loaded
+ *		kdata.)
  */
 
-static int loadpub(dstr *d)
+static kdata *kh_find(keyhalf *kh, const char *tag, int complainp)
 {
-  key_file *kf = CREATE(key_file);
+  knode *kn;
+  kdata *kd;
+  unsigned f;
 
-  if (key_open(kf, kr_pub, KOPEN_READ, keymoan, 0)) {
-    dstr_putf(d, "error reading public keyring `%s': %s",
-	      kr_pub, strerror(errno));
-    DESTROY(kf);
-    return (-1);
+  kn = sym_find(&kh->tab, tag, -1, sizeof(knode), &f);
+
+  if (f) {
+    if (kn->f & KNF_BROKEN) {
+      T( if (complainp)
+	   trace(T_KEYMGMT, "keymgmt: key `%s' marked as broken", tag); )
+      return (0);
+    }
+
+    kd = kn->kd;
+    if (kd) kd->ref++;
+    T( trace(T_KEYMGMT, "keymgmt: %scache hit for key `%s'",
+	     kd ? "" : "negative ", tag); )
+    return (kd);
+  } else {
+    kd = kh_load(kh, tag, complainp);
+    kn->kd = kd;
+    kn->kh = kh;
+    kn->f = 0;
+    if (!kd)
+      kn->f |= KNF_BROKEN;
+    else {
+      kd->kn = kn;
+      kd->ref++;
+    }
+    return (kd);
   }
-  kf_pub = kf;
-  T( trace(T_KEYMGMT, "keymgmt: loaded public keyring `%s'", kr_pub); )
-  return (0);
 }
 
-/* --- @km_reload@ --- *
+/* --- @kh_refresh@ --- *
  *
- * Arguments:	---
+ * Arguments:	@keyhalf *kh@ = pointer to the keyhalf
  *
- * Returns:	Zero if OK, nonzero to force reloading of keys.
+ * Returns:	Zero if nothing needs to be done; nonzero if peers should
+ *		refresh their keys.
  *
- * Use:		Checks the keyrings to see if they need reloading.
+ * Use:		Refreshes cached keys from files.
+ *
+ *		Each active knode is examined to see if a new key is
+ *		available: the return value is nonzero if any new keys are.
+ *		A key is considered new if its algorithms, public key, or
+ *		expiry time are/is different.
+ *
+ *		Stub knodes (with no kdata attached) are removed, so that a
+ *		later retry can succeed if the file has been fixed.  (This
+ *		doesn't count as a change, since no peers should be relying
+ *		on a nonexistent key.)
  */
 
-int km_reload(void)
+static int kh_refresh(keyhalf *kh)
 {
-  dstr d = DSTR_INIT;
-  key_file *kf;
-  int reload = 0;
-
-  /* --- Check the private key first --- */
-
-  if (fwatch_update(&w_priv, kr_priv)) {
-    T( trace(T_KEYMGMT, "keymgmt: private keyring updated: reloading..."); )
-    DRESET(&d);
-    if (loadpriv(&d))
-      a_warn("KEYMGMT", "bad-private-key", "%s", d.buf, A_END);
-    else
-      reload = 1;
-  }
-
-  /* --- Now check the public keys --- */
-
-  if (fwatch_update(&w_pub, kr_pub)) {
-    T( trace(T_KEYMGMT, "keymgmt: public keyring updated: reloading..."); )
-    kf = kf_pub;
-    DRESET(&d);
-    if (loadpub(&d))
-      a_warn("KEYMGMT", "bad-public-keyring", "%s", d.buf, A_END);
-    else {
-      reload = 1;
-      key_close(kf);
-      DESTROY(kf);
+  knode *kn;
+  kdata *kd;
+  sym_iter i;
+  int changep = 0;
+
+  if (!fwatch_update(&kh->w, kh->kr) || kh_reopen(kh))
+    return (0);
+
+  T( trace(T_KEYMGMT, "keymgmt: rescan %s keyring `%s'", kh->kind, kh->kr); )
+  for (sym_mkiter(&i, &kh->tab); (kn = sym_next(&i)) != 0; ) {
+    if (!kn->kd) {
+      T( trace(T_KEYMGMT, "keymgmt: discard stub entry for key `%s'",
+	       SYM_NAME(kn)); )
+      sym_remove(&kh->tab, kn);
+      continue;
     }
+    if ((kd = kh_load(kh, SYM_NAME(kn), 1)) == 0) {
+      if (!(kn->f & KNF_BROKEN)) {
+	T( trace(T_KEYMGMT, "keymgmt: failed to load new key `%s': "
+		 "marking it as broken",
+		 SYM_NAME(kn)); )
+	kn->f |= KNF_BROKEN;
+      }
+      continue;
+    }
+    kn->f &= ~KNF_BROKEN;
+    if (kd->t_exp == kn->kd->t_exp &&
+	km_samealgsp(kd, kn->kd) &&
+	G_EQ(kd->g, kd->kpub, kn->kd->kpub)) {
+      T( trace(T_KEYMGMT, "keymgmt: key `%s' unchanged", SYM_NAME(kn)); )
+      continue;
+    }
+    T( trace(T_KEYMGMT, "keymgmt: loaded new version of key `%s'",
+	     SYM_NAME(kn)); )
+    km_unref(kn->kd);
+    kd->kn = kn;
+    kn->kd = kd;
+    changep = 1;
   }
 
-  /* --- Done --- */
-
-  return (reload);
+  return (changep);
 }
 
+/*----- Main code ---------------------------------------------------------*/
+
+const char *tag_priv;
+kdata *master;
+
 /* --- @km_init@ --- *
  *
- * Arguments:	@const char *priv@ = private keyring file
- *		@const char *pub@ = public keyring file
- *		@const char *tag@ = tag to load
+ * Arguments:	@const char *privkr@ = private keyring file
+ *		@const char *pubkr@ = public keyring file
+ *		@const char *ptag@ = default private-key tag
  *
  * Returns:	---
  *
- * Use:		Initializes, and loads the private key.
+ * Use:		Initializes the key-management machinery, loading the
+ *		keyrings and so on.
  */
 
-void km_init(const char *priv, const char *pub, const char *tag)
+void km_init(const char *privkr, const char *pubkr, const char *ptag)
 {
-  dstr d = DSTR_INIT;
   const gchash *const *hh;
 
-  kr_priv = priv;
-  kr_pub = pub;
-  tag_priv = tag;
-  fwatch_init(&w_priv, kr_priv);
-  fwatch_init(&w_pub, kr_pub);
-
   for (hh = ghashtab; *hh; hh++) {
     if ((*hh)->hashsz > MAXHASHSZ) {
       die(EXIT_FAILURE, "INTERNAL ERROR: %s hash length %lu > MAXHASHSZ %d",
@@ -539,121 +791,97 @@ void km_init(const char *priv, const char *pub, const char *tag)
     }
   }
 
-  DRESET(&d);
-  if (loadpriv(&d))
-    die(EXIT_FAILURE, "%s", d.buf);
-  if (loadpub(&d))
-    die(EXIT_FAILURE, "%s", d.buf);
+  kh_init(&priv, privkr);
+  kh_init(&pub, pubkr);
+
+  tag_priv = ptag;
+  if ((master = km_findpriv(ptag)) == 0) exit(EXIT_FAILURE);
 }
 
-/* --- @km_getpubkey@ --- *
+/* --- @km_reload@ --- *
  *
- * Arguments:	@const char *tag@ = public key tag to load
- *		@ge *kpub@ = where to put the public key
- *		@time_t *t_exp@ = where to put the expiry time
+ * Arguments:	---
  *
- * Returns:	Zero if OK, nonzero if it failed.
+ * Returns:	Zero if OK, nonzero to force reloading of keys.
  *
- * Use:		Fetches a public key from the keyring.
+ * Use:		Checks the keyrings to see if they need reloading.
  */
 
-int km_getpubkey(const char *tag, ge *kpub, time_t *t_exp)
+int km_reload(void)
 {
-  key *k;
-  key_data **kd;
-  dstr t = DSTR_INIT;
-  const kgops **ko;
-  const char *e;
-  group *g = 0;
-  ge *p = 0;
-  algswitch a;
-  int rc = -1;
-
-  /* --- Find the key --- */
-
-  if (key_qtag(kf_pub, tag, &t, &k, &kd)) {
-    a_warn("KEYMGMT", "public-key", "%s", tag, "not-found", A_END);
-    goto done;
-  }
-
-  /* --- Look up the key type in the table --- */
-
-  for (ko = kgtab; *ko; ko++) {
-    if (strcmp((*ko)->ty, k->type) == 0)
-      goto tymatch;
-  }
-  a_warn("KEYMGMT",
-	 "public-key", "%s", t.buf,
-	 "unknown-type", "%s", k->type,
-	 A_END);
-  goto done;
-tymatch:;
-
-  /* --- Load the key --- */
-
-  if ((e = (*ko)->loadpub(*kd, &g, &p, &t)) != 0) {
-    a_warn("KEYMGMT", "public-key", "%s", t.buf, "bad", "%s", e, A_END);
-    goto done;
-  }
-
-  /* --- Ensure that the group is correct --- *
-   *
-   * Dodginess!	 We assume that if this works, our global group is willing to
-   * adopt this public element.  Probably reasonable.
-   */
-
-  if (!group_samep(gg, g)) {
-    a_warn("KEYMGMT", "public-key", "%s", t.buf, "incorrect-group", A_END);
-    goto done;
+  int changep = 0;
+  kdata *kd;
+
+  if (kh_refresh(&priv)) {
+    changep = 1;
+    kd = master->kn->kd;
+    if (kd != master) {
+      km_unref(master);
+      km_ref(kd);
+      master = kd;
+    }
   }
+  if (kh_refresh(&pub))
+    changep = 1;
+  return (changep);
+}
 
-  /* --- Check the public group element --- */
+/* --- @km_findpub@, @km_findpriv@ --- *
+ *
+ * Arguments:	@const char *tag@ = key tag to load
+ *
+ * Returns:	Pointer to the kdata object if successful, or null on error.
+ *
+ * Use:		Fetches a public or private key from the keyring.
+ */
 
-  if (group_check(gg, p)) {
-    a_warn("KEYMGMT",
-	   "public-key", "%s", t.buf,
-	   "bad-public-group-element",
-	   A_END);
-    goto done;
-  }
+kdata *km_findpub(const char *tag) { return (kh_find(&pub, tag, 1)); }
 
-  /* --- Check the algorithms --- */
+kdata *km_findpriv(const char *tag)
+{
+  kdata *kd;
 
-  if ((e = algs_get(&a, kf_pub, k)) != 0) {
-    a_warn("KEYMGMT",
-	   "public-key", "%s", t.buf,
-	   "bad-algorithm-selection", e,
-	   A_END);
-    goto done;
-  }
-  if (!algs_samep(&a, &algs)) {
-    a_warn("KEYMGMT",
-	   "public-key", "%s", t.buf,
-	   "algorithm-mismatch",
-	   A_END);
-    goto done;
-  }
+  /* Unpleasantness for the sake of compatibility. */
+  if (!tag && (kd = kh_find(&priv, "tripe", 0)) != 0) return (kd);
+  else return (kh_find(&priv, tag ? tag : "tripe-dh", 1));
+}
 
-  /* --- Dump the public key --- */
+/* --- @km_tag@ --- *
+ *
+ * Arguments:	@kdata *kd@ - pointer to the kdata object
+ *
+ * Returns:	A pointer to the short tag by which the kdata was loaded.
+ */
 
-  IF_TRACING(T_KEYMGMT, {
-    trace(T_KEYMGMT, "keymgmt: extracted public key `%s'", t.buf);
-    trace(T_CRYPTO, "crypto: p = %s", gestr(gg, p));
-  })
+const char *km_tag(kdata *kd) { return (SYM_NAME(kd->kn)); }
 
-  /* --- OK, accept the public key --- */
+/* --- @km_ref@ --- *
+ *
+ * Arguments:	@kdata *kd@ = pointer to the kdata object
+ *
+ * Returns:	---
+ *
+ * Use:		Claim a new reference to a kdata object.
+ */
 
-  *t_exp = k->exp;
-  G_COPY(gg, kpub, p);
-  rc = 0;
+void km_ref(kdata *kd) { kd->ref++; }
 
-  /* --- Tidy up --- */
+/* --- @km_unref@ --- *
+ *
+ * Arguments:	@kdata *kd@ = pointer to the kdata object
+ *
+ * Returns:	---
+ *
+ * Use:		Releases a reference to a kdata object.
+ */
 
-done:
-  if (p) G_DESTROY(g, p);
-  if (g) G_DESTROYGROUP(g);
-  dstr_destroy(&t);
-  return (rc);
+void km_unref(kdata *kd)
+{
+  if (--kd->ref) return;
+  if (kd->kpriv) mp_drop(kd->kpriv);
+  G_DESTROY(kd->g, kd->kpub);
+  xfree(kd->tag);
+  G_DESTROYGROUP(kd->g);
 }
 
 /*----- That's all, folks -------------------------------------------------*/