Use strbuf to store results in prompts_t.

UBsan pointed out another memcpy from NULL (again with length 0) in
the prompts_t system. When I looked at it, I realised that firstly
prompt_ensure_result_size was an early not-so-good implementation of
sgrowarray_nm that would benefit from being replaced with a call to
the real one, and secondly, the whole system for storing prompt
results should really have been replaced with strbufs with the no-move
option, because that's doing all the same jobs better.

So, now each prompt_t holds a strbuf in place of its previous manually
managed string. prompt_ensure_result_size is gone (the console
prompt-reading functions use strbuf_append, and everything else just
adds to the strbuf in the usual marshal.c way). New functions exist to
retrieve a prompt_t's result, either by reference or copied.

1 files changed, 6 insertions, 5 deletions

diff --git a/cmdgen.c b/cmdgen.c
index e7242f49..286c12e9 100644
--- a/cmdgen.c
+++ b/cmdgen.c
@@ -53,10 +53,10 @@ int console_get_userpass_input(prompts_t *p)
     int ret = 1;
     for (i = 0; i < p->n_prompts; i++) {
         if (promptsgot < nprompts) {
-            p->prompts[i]->result = dupstr(prompts[promptsgot++]);
+            prompt_set_result(p->prompts[i], prompts[promptsgot++]);
             if (cgtest_verbose)
                 printf("  prompt \"%s\": response \"%s\"\n",
-                       p->prompts[i]->prompt, p->prompts[i]->result);
+                       p->prompts[i]->prompt, p->prompts[i]->result->s);
         } else {
             promptsgot++;           /* track number of requests anyway */
             ret = 0;
@@ -777,7 +777,7 @@ int main(int argc, char **argv)
                     perror("puttygen: unable to read passphrase");
                     RETURN(1);
                 } else {
-                    old_passphrase = dupstr(p->prompts[0]->result);
+                    old_passphrase = prompt_get_result(p->prompts[0]);
                     free_prompts(p);
                 }
             }
@@ -921,12 +921,13 @@ int main(int argc, char **argv)
             perror("puttygen: unable to read new passphrase");
             RETURN(1);
         } else {
-            if (strcmp(p->prompts[0]->result, p->prompts[1]->result)) {
+            if (strcmp(prompt_get_result_ref(p->prompts[0]),
+                       prompt_get_result_ref(p->prompts[1]))) {
                 free_prompts(p);
                 fprintf(stderr, "puttygen: passphrases do not match\n");
                 RETURN(1);
             }
-            new_passphrase = dupstr(p->prompts[0]->result);
+            new_passphrase = prompt_get_result(p->prompts[0]);
             free_prompts(p);
         }
     }