X-Git-Url: https://git.distorted.org.uk/~mdw/tripe/blobdiff_plain/00e64b67d321bf53224d546dcba58c52834a7b79..c55f55afc693f452bcfa2ddd2af50d3216a9c951:/keymgmt.c

diff --git a/keymgmt.c b/keymgmt.c
index 54a31b0b..e05706ac 100644
--- a/keymgmt.c
+++ b/keymgmt.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: keymgmt.c,v 1.3 2001/06/22 19:40:36 mdw Exp $
+ * $Id: keymgmt.c,v 1.6 2004/04/18 18:08:11 mdw Exp $
  *
  * Key loading and storing
  *
@@ -26,28 +26,15 @@
  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: keymgmt.c,v $
- * Revision 1.3  2001/06/22 19:40:36  mdw
- * Support expiry of other peers' public keys.
- *
- * Revision 1.2  2001/06/19 22:07:09  mdw
- * Cosmetic fixes.
- *
- * Revision 1.1  2001/02/03 20:26:37  mdw
- * Initial checkin.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "tripe.h"
 
 /*----- Global variables --------------------------------------------------*/
 
-mpmont mg;
-dh_priv kpriv;
+group *gg;
+mp *kpriv;
+algswitch algs;
 
 /*----- Static variables --------------------------------------------------*/
 
@@ -55,6 +42,250 @@ static key_file *kf_pub;
 static const char *kr_priv, *kr_pub, *tag_priv;
 static fwatch w_priv, w_pub;
 
+/*----- Key groups --------------------------------------------------------*/
+
+typedef struct kgops {
+  const char *ty;
+  const char *(*loadpriv)(key_data *, group **, mp **, dstr *);
+  const char *(*loadpub)(key_data *, group **, ge **, 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;
+
+  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);
+}
+
+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;
+
+  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);
+}
+
+static const kgops kgec_ops = { "tripe-ec", kgec_priv, kgec_pub };
+
+/* --- Table of supported key types --- */
+
+static const kgops *kgtab[] = { &kgdh_ops, &kgec_ops, 0 };
+
+/*----- Algswitch stuff ---------------------------------------------------*/
+
+/* --- @algs_get@ --- *
+ *
+ * Arguments:	@algswitch *a@ = where to put the algorithms
+ *		@key_file *kf@ = key file (for some stupid reason)
+ *		@key *k@ = key to inspect
+ *
+ * Returns:	Null if OK, or an error message.
+ *
+ * Use:		Extracts an algorithm choice from a key.
+ */
+
+static const char *algs_get(algswitch *a, key_file *kf, key *k)
+{
+  const char *p;
+  char *q;
+  dstr d = DSTR_INIT;
+  const char *e;
+
+#define FAIL(msg) do { e = msg; goto done; } while (0)
+
+  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)
+    FAIL("unknown hash function");
+
+  if ((p = key_getattr(kf, k, "mgf")) != 0) {
+    dstr_reset(&d);
+    dstr_putf(&d, "%s-mgf");
+    p = d.buf;
+  }
+  if ((a->mgf = gcipher_byname(p)) == 0)
+    FAIL("unknown MGF cipher");
+
+  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)
+      FAIL("unknown message authentication code");
+    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;
+    }
+  } else {
+    dstr_reset(&d);
+    dstr_putf(&d, "%s-hmac", a->h->name);
+    if ((a->m = gmac_byname(d.buf)) == 0)
+      FAIL("failed to derive HMAC from hash function");
+    a->tagsz = a->h->hashsz/2;
+  }
+
+  e = 0;
+done:
+  dstr_destroy(&d);
+  return (e);
+}
+
+/* --- @algs_check@ --- *
+ *
+ * Arguments:	@algswitch *a@ = a choice of algorithms
+ *		@const group *g@ = the group we're working in
+ *
+ * Returns:	Null if OK, or an error message.
+ *
+ * Use:		Checks an algorithm choice for sensibleness.  This also
+ *		derives some useful information from the choices, and you
+ *		must call this before committing the algorithm selection
+ *		for use by @keyset@ functions.
+ */
+
+static const char *algs_check(algswitch *a, const group *g)
+{
+  /* --- Derive the key sizes --- *
+   *
+   * Must ensure that we have non-empty keys.  This isn't ideal, but it
+   * provides a handy sanity check.
+   */
+
+  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");
+
+  /* --- Ensure that the tag size is sane --- */
+
+  if (a->tagsz > a->m->hashsz) return ("tag length too large");
+
+  /* --- Ensure the MGF accepts hashes as keys --- */
+
+  if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz)
+    return ("MGF not suitable -- restrictive key schedule");
+
+  /* --- All ship-shape and Bristol-fashion --- */
+
+  return (0);
+}
+
+/* --- @algs_samep@ --- *
+ *
+ * Arguments:	@const algswitch *a, *aa@ = two algorithm selections
+ *
+ * Returns:	Nonzero if the two 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)
+{
+  return (a->c == aa->c && a->mgf == aa->mgf && a->h == aa->h &&
+	  a->m == aa->m && a->tagsz == aa->tagsz);
+}
+
 /*----- Main code ---------------------------------------------------------*/
 
 /* --- @keymoan@ --- *
@@ -70,60 +301,128 @@ static fwatch w_priv, w_pub;
  */
 
 static void keymoan(const char *file, int line, const char *msg, void *p)
-{
-  a_warn("%s:%i: error: %s", file, line, msg);
-}
+  { a_warn("%s:%i: error: %s", file, line, msg); }
 
 /* --- @loadpriv@ --- *
  *
  * Arguments:	@dstr *d@ = string to write errors in
- *		@dh_priv *dh@ = where to store the key
  *
  * Returns:	Zero if OK, nonzero on error.
  *
  * Use:		Loads the private key from its keyfile.
  */
 
-static int loadpriv(dstr *d, dh_priv *dh)
+static int loadpriv(dstr *d)
 {
   key_file kf;
-  key_packstruct kps[DH_PRIVFETCHSZ];
-  key_packdef *kp;
-  dh_priv mydh;
-  int rc = 0;
-  int e;
+  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));
-    rc = -1;
-  } else {
-    T( trace(T_KEYMGMT, "keymgmt: loaded private keyring `%s'", kr_priv); )
-    kp = key_fetchinit(dh_privfetch, kps, &mydh);
-    if ((e = key_fetchbyname(kp, &kf, tag_priv)) != 0) {
-      dstr_putf(d, "error loading private key `%s': %s",
-		tag_priv, key_strerror(e));
-      rc = -1;
-    } else {
-      dh->dp.p = MP_COPY(mydh.dp.p);
-      dh->dp.q = MP_COPY(mydh.dp.q);
-      dh->dp.g = MP_COPY(mydh.dp.g);
-      dh->x = MP_COPY(mydh.x);
-      dh->y = MP_COPY(mydh.y);      
-      IF_TRACING(T_KEYMGMT, {
-	trace(T_KEYMGMT, "keymgmt: extracted private key `%s'", tag_priv);
-	IF_TRACING(T_CRYPTO, {
-	  trace(T_CRYPTO, "crypto: p = %s", mpstr(kpriv.dp.p));
-	  trace(T_CRYPTO, "crypto: q = %s", mpstr(kpriv.dp.q));
-	  trace(T_CRYPTO, "crypto: g = %s", mpstr(kpriv.dp.g));
-	  trace(T_CRYPTO, "crypto: x = %s", mpstr(kpriv.x));
-	  trace(T_CRYPTO, "crypto: g^x = %s", mpstr(kpriv.y));
-	})
-      })
+    goto done_0;
+  }
+
+  /* --- Find the private key --- */
+
+  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;
+  }
+
+  /* --- 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:;
+
+  /* --- Load the key --- */
+
+  if ((e = (*ko)->loadpriv(kd, &g, &x, &t)) != 0) {
+    dstr_putf(d, "error reading private key `%s': %s", t.buf, e);
+    goto done_1;
+  }
+
+  /* --- Check that the key is sensible --- */
+
+  if ((e = G_CHECK(g, &rand_global)) != 0) {
+    dstr_putf(d, "bad group in private key `%s': %s", t.buf, e);
+    goto done_1;
+  }
+
+  /* --- Collect the algorithms --- */
+
+  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;
+  }
+
+  /* --- Good, we're happy --- *
+   *
+   * 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.
+   */
+
+  if (gg) {
+    if (!group_samep(g, gg)) {
+      dstr_putf(d, "private key `%s' has different group", t.buf);
+      goto done_1;
     }
-    key_fetchdone(kp);
-    key_close(&kf);
+    G_DESTROYGROUP(gg);
   }
+  if (kpriv)
+    mp_drop(kpriv);
+
+  /* --- Dump out the group --- */
+
+  IF_TRACING(T_KEYMGMT, {
+    trace(T_KEYMGMT, "keymgmt: extracted private key `%s'", 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: mac = %s/%lu",
+	    a.m->name, (unsigned long)a.tagsz * 8);
+    })
+  })
+
+  /* --- Success! --- */
+
+  gg = g; g = 0;
+  algs = a;
+  kpriv = x; x = 0;
+  rc = 0;
+
+  /* --- Tidy up --- */
+
+done_1:
+  key_close(&kf);
+done_0:
+  dstr_destroy(&t);
+  if (x) mp_drop(x);
+  if (g) G_DESTROYGROUP(g);
   return (rc);
 }
 
@@ -163,7 +462,6 @@ static int loadpub(dstr *d)
 int km_interval(void)
 {
   dstr d = DSTR_INIT;
-  dh_priv dh;
   key_file *kf;
   int reload = 0;
 
@@ -172,15 +470,10 @@ int km_interval(void)
   if (fwatch_update(&w_priv, kr_priv)) {
     T( trace(T_KEYMGMT, "keymgmt: private keyring updated: reloading..."); )
     DRESET(&d);
-    if (loadpriv(&d, &dh))
+    if (loadpriv(&d))
       a_warn("%s -- ignoring changes", d.buf);
-    else {
+    else
       reload = 1;
-      mpmont_destroy(&mg);
-      dh_privfree(&kpriv);
-      kpriv = dh;
-      mpmont_create(&mg, kpriv.dp.p);
-    }
   }
 
   /* --- Now check the public keys --- */
@@ -217,6 +510,7 @@ int km_interval(void)
 void km_init(const char *priv, const char *pub, const char *tag)
 {
   dstr d = DSTR_INIT;
+  const gchash *const *hh;
 
   kr_priv = priv;
   kr_pub = pub;
@@ -224,10 +518,16 @@ void km_init(const char *priv, const char *pub, const char *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",
+	  (*hh)->name, (unsigned long)(*hh)->hashsz, MAXHASHSZ);
+    }
+  }
+
   DRESET(&d);
-  if (loadpriv(&d, &kpriv))
+  if (loadpriv(&d))
     die(EXIT_FAILURE, "%s", d.buf);
-  mpmont_create(&mg, kpriv.dp.p);
   if (loadpub(&d))
     die(EXIT_FAILURE, "%s", d.buf);
 }
@@ -235,7 +535,7 @@ void km_init(const char *priv, const char *pub, const char *tag)
 /* --- @km_getpubkey@ --- *
  *
  * Arguments:	@const char *tag@ = public key tag to load
- *		@dh_pub *kpub@ = where to put the public key
+ *		@ge *kpub@ = where to put the public key
  *		@time_t *t_exp@ = where to put the expiry time
  *
  * Returns:	Zero if OK, nonzero if it failed.
@@ -243,45 +543,91 @@ void km_init(const char *priv, const char *pub, const char *tag)
  * Use:		Fetches a public key from the keyring.
  */
 
-int km_getpubkey(const char *tag, dh_pub *kpub, time_t *t_exp)
+int km_getpubkey(const char *tag, ge *kpub, time_t *t_exp)
 {
-  key_packstruct kps[DH_PUBFETCHSZ];
-  key_packdef *kp;
   key *k;
-  dh_pub dp;
-  int e;
+  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("public key `%s' not found in keyring `%s'", tag, kr_pub);
+    goto done;
+  }
 
-  kp = key_fetchinit(dh_pubfetch, kps, &dp);
-  if ((k = key_bytag(kf_pub, tag)) == 0)
-    e = KERR_NOTFOUND;
-  else
-    e = key_fetch(kp, k);
-  key_fetchdone(kp);
-  if (e) {
-    a_warn("error loading public key `%s': %s", tag, key_strerror(e));
-    return (-1);
+  /* --- Look up the key type in the table --- */
+
+  for (ko = kgtab; *ko; ko++) {
+    if (strcmp((*ko)->ty, k->type) == 0)
+      goto tymatch;
+  }
+  a_warn("public key `%s' has unknown type `%s'", t.buf, k->type);
+  goto done;
+tymatch:;
+
+  /* --- Load the key --- */
+
+  if ((e = (*ko)->loadpub(kd, &g, &p, &t)) != 0) {
+    a_warn("error reading public key `%s': %s", t.buf, e);
+    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("public key `%s' has incorrect group", t.buf);
+    goto done;
+  }
+
+  /* --- Check the public group element --- */
+
+  if (group_check(gg, p)) {
+    a_warn("public key `%s' has bad public group element", t.buf);
+    goto done;
+  }
+
+  /* --- Check the algorithms --- */
+
+  if ((e = algs_get(&a, kf_pub, k)) != 0) {
+    a_warn("public key `%s' has bad algorithm selection: %s", t.buf, e);
+    goto done;
+  }
+  if (!algs_samep(&a, &algs)) {    
+    a_warn("public key `%s' specifies different algorithms", t.buf);
+    goto done;
   }
+
+  /* --- Dump the public key --- */
+
   IF_TRACING(T_KEYMGMT, {
-    trace(T_KEYMGMT, "keymgmt: extracted public key `%s'", tag);
-    IF_TRACING(T_CRYPTO, {
-      trace(T_CRYPTO, "crypto: p = %s", mpstr(dp.dp.p));
-      trace(T_CRYPTO, "crypto: q = %s", mpstr(dp.dp.q));
-      trace(T_CRYPTO, "crypto: g = %s", mpstr(dp.dp.g));
-      trace(T_CRYPTO, "crypto: g^x = %s", mpstr(dp.y));
-    })
+    trace(T_KEYMGMT, "keymgmt: extracted public key `%s'", t.buf);
+    trace(T_CRYPTO, "crypto: p = %s", gestr(gg, p));
   })
-  if (!mp_eq(dp.dp.p, kpriv.dp.p) ||
-      !mp_eq(dp.dp.q, kpriv.dp.q) ||
-      !mp_eq(dp.dp.g, kpriv.dp.g)) {
-    a_warn("public key `%s' has different group from private key", tag);
-    return (-1);
-  }
-  kpub->dp.p = MP_COPY(dp.dp.p);
-  kpub->dp.q = MP_COPY(dp.dp.q);
-  kpub->dp.g = MP_COPY(dp.dp.g);
-  kpub->y = MP_COPY(dp.y);
+
+  /* --- OK, accept the public key --- */
+
   *t_exp = k->exp;
-  return (0);
+  G_COPY(gg, kpub, p);
+  rc = 0;
+
+  /* --- Tidy up --- */
+
+done:
+  if (p) G_DESTROY(g, p);
+  if (g) G_DESTROYGROUP(g);
+  dstr_destroy(&t);
+  return (rc);
 }
 
 /*----- That's all, folks -------------------------------------------------*/