Windows Pageant: use nicer key-type strings.

If you load a certified key into Windows Pageant, the official SSH id
for the key type is so long that it overflows its space in the list
box and overlaps the key fingerprint hash.

This commit introduces yet another footling little ssh_keyalg method
which returns a shorter human-readable description of the key type,
and uses that in the Windows Pageant list box only.

(Not in the Unix Pageant list, though, because being output to stdout,
that seems like something people are more likely to want to
machine-read, which firstly means we shouldn't change it lightly, and
secondly, if we did change it we'd want to avoid having a variable
number of spaces in the replacement key type text.)

crypto/dsa.c

@@ -490,6 +490,8 @@ static void dsa_sign(ssh_key *key, ptrlen data, unsigned flags, BinarySink *bs)
     mp_free(s);
 }
 
+static char *dsa_alg_desc(const ssh_keyalg *self) { return dupstr("DSA"); }
+
 const ssh_keyalg ssh_dsa = {
     .new_pub = dsa_new_pub,
     .new_priv = dsa_new_priv,
@@ -508,6 +510,7 @@ const ssh_keyalg ssh_dsa = {
     .pubkey_bits = dsa_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = dsa_alg_desc,
     .ssh_id = "ssh-dss",
     .cache_id = "dss",
 };

crypto/ecc-ssh.c

@@ -325,6 +325,9 @@ struct ecsign_extra {
     const unsigned char *oid;
     int oidlen;
 
+    /* Human-readable algorithm description */
+    const char *alg_desc;
+
     /* Some EdDSA instances prefix a string to all hash preimages, to
      * disambiguate which signature variant they're being used with */
     ptrlen hash_prefix;
@@ -1251,9 +1254,16 @@ static void eddsa_sign(ssh_key *key, ptrlen data,
     mp_free(s);
 }
 
+static char *ec_alg_desc(const ssh_keyalg *self)
+{
+    const struct ecsign_extra *extra =
+        (const struct ecsign_extra *)self->extra;
+    return dupstr(extra->alg_desc);
+}
+
 static const struct ecsign_extra sign_extra_ed25519 = {
     ec_ed25519, &ssh_sha512,
-    NULL, 0, PTRLEN_DECL_LITERAL(""),
+    NULL, 0, "Ed25519", PTRLEN_DECL_LITERAL(""),
 };
 const ssh_keyalg ssh_ecdsa_ed25519 = {
     .new_pub = eddsa_new_pub,
@@ -1273,6 +1283,7 @@ const ssh_keyalg ssh_ecdsa_ed25519 = {
     .pubkey_bits = ec_shared_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = ec_alg_desc,
     .ssh_id = "ssh-ed25519",
     .cache_id = "ssh-ed25519",
     .extra = &sign_extra_ed25519,
@@ -1280,7 +1291,7 @@ const ssh_keyalg ssh_ecdsa_ed25519 = {
 
 static const struct ecsign_extra sign_extra_ed448 = {
     ec_ed448, &ssh_shake256_114bytes,
-    NULL, 0, PTRLEN_DECL_LITERAL("SigEd448\0\0"),
+    NULL, 0, "Ed448", PTRLEN_DECL_LITERAL("SigEd448\0\0"),
 };
 const ssh_keyalg ssh_ecdsa_ed448 = {
     .new_pub = eddsa_new_pub,
@@ -1300,6 +1311,7 @@ const ssh_keyalg ssh_ecdsa_ed448 = {
     .pubkey_bits = ec_shared_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = ec_alg_desc,
     .ssh_id = "ssh-ed448",
     .cache_id = "ssh-ed448",
     .extra = &sign_extra_ed448,
@@ -1311,7 +1323,7 @@ static const unsigned char nistp256_oid[] = {
 };
 static const struct ecsign_extra sign_extra_nistp256 = {
     ec_p256, &ssh_sha256,
-    nistp256_oid, lenof(nistp256_oid),
+    nistp256_oid, lenof(nistp256_oid), "NIST p256",
 };
 const ssh_keyalg ssh_ecdsa_nistp256 = {
     .new_pub = ecdsa_new_pub,
@@ -1331,6 +1343,7 @@ const ssh_keyalg ssh_ecdsa_nistp256 = {
     .pubkey_bits = ec_shared_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = ec_alg_desc,
     .ssh_id = "ecdsa-sha2-nistp256",
     .cache_id = "ecdsa-sha2-nistp256",
     .extra = &sign_extra_nistp256,
@@ -1342,7 +1355,7 @@ static const unsigned char nistp384_oid[] = {
 };
 static const struct ecsign_extra sign_extra_nistp384 = {
     ec_p384, &ssh_sha384,
-    nistp384_oid, lenof(nistp384_oid),
+    nistp384_oid, lenof(nistp384_oid), "NIST p384",
 };
 const ssh_keyalg ssh_ecdsa_nistp384 = {
     .new_pub = ecdsa_new_pub,
@@ -1362,6 +1375,7 @@ const ssh_keyalg ssh_ecdsa_nistp384 = {
     .pubkey_bits = ec_shared_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = ec_alg_desc,
     .ssh_id = "ecdsa-sha2-nistp384",
     .cache_id = "ecdsa-sha2-nistp384",
     .extra = &sign_extra_nistp384,
@@ -1373,7 +1387,7 @@ static const unsigned char nistp521_oid[] = {
 };
 static const struct ecsign_extra sign_extra_nistp521 = {
     ec_p521, &ssh_sha512,
-    nistp521_oid, lenof(nistp521_oid),
+    nistp521_oid, lenof(nistp521_oid), "NIST p521",
 };
 const ssh_keyalg ssh_ecdsa_nistp521 = {
     .new_pub = ecdsa_new_pub,
@@ -1393,6 +1407,7 @@ const ssh_keyalg ssh_ecdsa_nistp521 = {
     .pubkey_bits = ec_shared_pubkey_bits,
     .supported_flags = nullkey_supported_flags,
     .alternate_ssh_id = nullkey_alternate_ssh_id,
+    .alg_desc = ec_alg_desc,
     .ssh_id = "ecdsa-sha2-nistp521",
     .cache_id = "ecdsa-sha2-nistp521",
     .extra = &sign_extra_nistp521,

crypto/openssh-certs.c

@@ -216,6 +216,7 @@ static int opensshcert_pubkey_bits(const ssh_keyalg *self, ptrlen blob);
 static unsigned opensshcert_supported_flags(const ssh_keyalg *self);
 static const char *opensshcert_alternate_ssh_id(const ssh_keyalg *self,
                                                 unsigned flags);
+static char *opensshcert_alg_desc(const ssh_keyalg *self);
 static const ssh_keyalg *opensshcert_related_alg(const ssh_keyalg *self,
                                                  const ssh_keyalg *base);
 
@@ -269,6 +270,7 @@ static const ssh_keyalg *opensshcert_related_alg(const ssh_keyalg *self,
         .pubkey_bits = opensshcert_pubkey_bits,                         \
         .supported_flags = opensshcert_supported_flags,                 \
         .alternate_ssh_id = opensshcert_alternate_ssh_id,               \
+        .alg_desc = opensshcert_alg_desc,                               \
         .related_alg = opensshcert_related_alg,                         \
         .ssh_id = ssh_alg_id_prefix "-cert-v01@openssh.com",            \
         .cache_id = "opensshcert-" ssh_key_id_prefix,                   \
@@ -898,6 +900,14 @@ static const char *opensshcert_alternate_ssh_id(const ssh_keyalg *self,
     return self->ssh_id;
 }
 
+static char *opensshcert_alg_desc(const ssh_keyalg *self)
+{
+    char *base_desc = ssh_keyalg_desc(self->base_alg);
+    char *our_desc = dupcat(base_desc, " cert");
+    sfree(base_desc);
+    return our_desc;
+}
+
 static const ssh_keyalg *opensshcert_related_alg(const ssh_keyalg *self,
                                                  const ssh_keyalg *base)
 {

crypto/rsa.c

@@ -859,6 +859,8 @@ const char *ssh_rsa_alternate_ssh_id(const ssh_keyalg *self, unsigned flags)
     return self->ssh_id;
 }
 
+static char *rsa2_alg_desc(const ssh_keyalg *self) { return dupstr("RSA"); }
+
 static const struct ssh2_rsa_extra
     rsa_extra = { 0 },
     rsa_sha256_extra = { SSH_AGENT_RSA_SHA2_256 },
@@ -880,6 +882,7 @@ static const struct ssh2_rsa_extra
     .components = rsa2_components,              \
     .base_key = nullkey_base_key,               \
     .pubkey_bits = rsa2_pubkey_bits,            \
+    .alg_desc = rsa2_alg_desc,                  \
     .cache_id = "rsa2"
 
 const ssh_keyalg ssh_rsa = {

ssh.h

@@ -857,6 +857,7 @@ struct ssh_keyalg {
     int (*pubkey_bits) (const ssh_keyalg *self, ptrlen blob);
     unsigned (*supported_flags) (const ssh_keyalg *self);
     const char *(*alternate_ssh_id) (const ssh_keyalg *self, unsigned flags);
+    char *(*alg_desc)(const ssh_keyalg *self);
     /* The following methods can be NULL if !is_certificate */
     const ssh_keyalg *(*related_alg)(const ssh_keyalg *self,
                                      const ssh_keyalg *base);
@@ -925,6 +926,8 @@ static inline const unsigned ssh_keyalg_supported_flags(const ssh_keyalg *self)
 static inline const char *ssh_keyalg_alternate_ssh_id(
     const ssh_keyalg *self, unsigned flags)
 { return self->alternate_ssh_id(self, flags); }
+static inline char *ssh_keyalg_desc(const ssh_keyalg *self)
+{ return self->alg_desc(self); }
 static inline const ssh_keyalg *ssh_keyalg_related_alg(
     const ssh_keyalg *self, const ssh_keyalg *base)
 { return self->related_alg(self, base); }

windows/pageant.c

@@ -346,7 +346,7 @@ static void keylist_update_callback(
          * Expect the fingerprint to contain two words: bit count and
          * hash.
          */
-        put_dataz(disp->alg, "ssh1");
+        put_dataz(disp->alg, "SSH-1");
         put_datapl(disp->bits, ptrlen_get_word(&fingerprint, " "));
         put_datapl(disp->hash, ptrlen_get_word(&fingerprint, " "));
         break;
@@ -357,7 +357,21 @@ static void keylist_update_callback(
          * Expect the fingerprint to contain three words: algorithm
          * name, bit count, hash.
          */
-        put_datapl(disp->alg, ptrlen_get_word(&fingerprint, " "));
+        const ssh_keyalg *alg = pubkey_blob_to_alg(
+            ptrlen_from_strbuf(key->blob));
+
+        ptrlen keytype_word = ptrlen_get_word(&fingerprint, " ");
+        if (alg) {
+            /* Use our own human-legible algorithm names if available,
+             * because they fit better in the space. (Certificate key
+             * algorithm names in particular are terribly long.) */
+            char *alg_desc = ssh_keyalg_desc(alg);
+            put_dataz(disp->alg, alg_desc);
+            sfree(alg_desc);
+        } else {
+            put_datapl(disp->alg, keytype_word);
+        }
+
         put_datapl(disp->bits, ptrlen_get_word(&fingerprint, " "));
         put_datapl(disp->hash, ptrlen_get_word(&fingerprint, " "));
 
@@ -368,8 +382,6 @@ static void keylist_update_callback(
          * overlap into the bits column without colliding with
          * pointless text.
          */
-        const ssh_keyalg *alg = pubkey_blob_to_alg(
-            ptrlen_from_strbuf(key->blob));
         if (!(alg == &ssh_dsa || alg == &ssh_rsa))
             strbuf_clear(disp->bits);
       }