Refactor the key-components mechanism a bit.

Having recently pulled it out into its own file, I think it could also
do with a bit of tidying. In this rework:

 - the substructure for a single component now has a globally visible
   struct tag, so you can make a variable pointing at it, saving
   verbiage in every piece of code looping over a key_components

 - the 'is_mp_int' flag has been replaced with a type enum, so that
   more types can be added without further upheaval

 - the printing loop in cmdgen.c for puttygen --dump has factored out
   the initial 'name=' prefix on each line so that it isn't repeated
   per component type

 - the storage format for text components is now a strbuf rather than
   a plain char *, which I think is generally more useful.

cmdgen.c

@@ -1312,16 +1312,23 @@ int main(int argc, char **argv)
         }
 
         for (size_t i = 0; i < kc->ncomponents; i++) {
-            if (kc->components[i].is_mp_int) {
-                char *hex = mp_get_hex(kc->components[i].mp);
-                fprintf(fp, "%s=0x%s\n", kc->components[i].name, hex);
+            key_component *comp = &kc->components[i];
+            fprintf(fp, "%s=", comp->name);
+            switch (comp->type) {
+              case KCT_MPINT: {
+                char *hex = mp_get_hex(comp->mp);
+                fprintf(fp, "0x%s\n", hex);
                 smemclr(hex, strlen(hex));
                 sfree(hex);
-            } else {
-                fprintf(fp, "%s=\"", kc->components[i].name);
-                write_c_string_literal(fp, ptrlen_from_asciz(
-                                           kc->components[i].text));
+                break;
+              }
+              case KCT_TEXT:
+                fputs("\"", fp);
+                write_c_string_literal(fp, ptrlen_from_strbuf(comp->str));
                 fputs("\"\n", fp);
+                break;
+              default:
+                unreachable("bad key component type");
             }
         }
 

ssh.h

@@ -542,16 +542,20 @@ struct eddsa_key {
 WeierstrassPoint *ecdsa_public(mp_int *private_key, const ssh_keyalg *alg);
 EdwardsPoint *eddsa_public(mp_int *private_key, const ssh_keyalg *alg);
 
+typedef enum KeyComponentType {
+    KCT_TEXT, KCT_MPINT
+} KeyComponentType;
+typedef struct key_component {
+    char *name;
+    KeyComponentType type;
+    union {
+        strbuf *str;                   /* used for KCT_TEXT */
+        mp_int *mp;                    /* used for KCT_MPINT */
+    };
+} key_component;
 typedef struct key_components {
     size_t ncomponents, componentsize;
-    struct {
-        char *name;
-        bool is_mp_int;
-        union {
-            char *text;
-            mp_int *mp;
-        };
-    } *components;
+    key_component *components;
 } key_components;
 key_components *key_components_new(void);
 void key_components_add_text(key_components *kc,

test/testcrypt-func.h

@@ -309,7 +309,7 @@ FUNC(uint, ssh_key_public_bits, ARG(keyalg, self), ARG(val_string_ptrlen, blob))
 FUNC(uint, key_components_count, ARG(val_keycomponents, kc))
 FUNC(opt_val_string_asciz_const, key_components_nth_name,
      ARG(val_keycomponents, kc), ARG(uint, n))
-FUNC(opt_val_string_asciz_const, key_components_nth_str,
+FUNC(opt_val_string, key_components_nth_str,
      ARG(val_keycomponents, kc), ARG(uint, n))
 FUNC(opt_val_mpint, key_components_nth_mp, ARG(val_keycomponents, kc),
      ARG(uint, n))

test/testcrypt.c

@@ -1227,16 +1227,18 @@ const char *key_components_nth_name(key_components *kc, size_t n)
     return (n >= kc->ncomponents ? NULL :
             kc->components[n].name);
 }
-const char *key_components_nth_str(key_components *kc, size_t n)
+strbuf *key_components_nth_str(key_components *kc, size_t n)
 {
-    return (n >= kc->ncomponents ? NULL :
-            kc->components[n].is_mp_int ? NULL :
-            kc->components[n].text);
+    if (n >= kc->ncomponents)
+        return NULL;
+    if (kc->components[n].type != KCT_TEXT)
+        return NULL;
+    return strbuf_dup(ptrlen_from_strbuf(kc->components[n].str));
 }
 mp_int *key_components_nth_mp(key_components *kc, size_t n)
 {
     return (n >= kc->ncomponents ? NULL :
-            !kc->components[n].is_mp_int ? NULL :
+            kc->components[n].type != KCT_MPINT ? NULL :
             mp_copy(kc->components[n].mp));
 }
 

utils/key_components.c

@@ -16,8 +16,8 @@ void key_components_add_text(key_components *kc,
     sgrowarray(kc->components, kc->componentsize, kc->ncomponents);
     size_t n = kc->ncomponents++;
     kc->components[n].name = dupstr(name);
-    kc->components[n].is_mp_int = false;
-    kc->components[n].text = dupstr(value);
+    kc->components[n].type = KCT_TEXT;
+    kc->components[n].str = strbuf_dup_nm(ptrlen_from_asciz(value));
 }
 
 void key_components_add_mp(key_components *kc,
@@ -26,19 +26,24 @@ void key_components_add_mp(key_components *kc,
     sgrowarray(kc->components, kc->componentsize, kc->ncomponents);
     size_t n = kc->ncomponents++;
     kc->components[n].name = dupstr(name);
-    kc->components[n].is_mp_int = true;
+    kc->components[n].type = KCT_MPINT;
     kc->components[n].mp = mp_copy(value);
 }
 
 void key_components_free(key_components *kc)
 {
     for (size_t i = 0; i < kc->ncomponents; i++) {
-        sfree(kc->components[i].name);
-        if (kc->components[i].is_mp_int) {
-            mp_free(kc->components[i].mp);
-        } else {
-            smemclr(kc->components[i].text, strlen(kc->components[i].text));
-            sfree(kc->components[i].text);
+        key_component *comp = &kc->components[i];
+        sfree(comp->name);
+        switch (comp->type) {
+          case KCT_MPINT:
+            mp_free(comp->mp);
+            break;
+          case KCT_TEXT:
+            strbuf_free(comp->str);
+            break;
+          default:
+            unreachable("bad key component type");
         }
     }
     sfree(kc->components);