Fix potential memory leak in ASN1_TIME_to_generalizedtime()

If ret is allocated, it may be leaked on error.

(Imported from upstream's cdfb7809b6a365a0a7874afd8f8778c5c572f267 and
ffcdb0e6efb6fb7033b2cd29e8cca2e2fe355c14.)

Change-Id: I50ed9ad072cf80461d9527d0834b596a8c32e3d3
Reviewed-on: https://boringssl-review.googlesource.com/14315
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/crypto/asn1/a_time.c b/crypto/asn1/a_time.c
index 4b58429..c962c0b 100644
--- a/crypto/asn1/a_time.c
+++ b/crypto/asn1/a_time.c
@@ -114,7 +114,7 @@
 ASN1_GENERALIZEDTIME *ASN1_TIME_to_generalizedtime(ASN1_TIME *t,
                                                    ASN1_GENERALIZEDTIME **out)
 {
-    ASN1_GENERALIZEDTIME *ret;
+    ASN1_GENERALIZEDTIME *ret = NULL;
     char *str;
     int newlen;
 
@@ -123,22 +123,21 @@
 
     if (!out || !*out) {
         if (!(ret = ASN1_GENERALIZEDTIME_new()))
-            return NULL;
-        if (out)
-            *out = ret;
-    } else
+            goto err;
+    } else {
         ret = *out;
+    }
 
     /* If already GeneralizedTime just copy across */
     if (t->type == V_ASN1_GENERALIZEDTIME) {
         if (!ASN1_STRING_set(ret, t->data, t->length))
-            return NULL;
-        return ret;
+            goto err;
+        goto done;
     }
 
     /* grow the string */
     if (!ASN1_STRING_set(ret, NULL, t->length + 2))
-        return NULL;
+        goto err;
     /* ASN1_STRING_set() allocated 'len + 1' bytes. */
     newlen = t->length + 2 + 1;
     str = (char *)ret->data;
@@ -150,9 +149,18 @@
 
     BUF_strlcat(str, (char *)t->data, newlen);
 
-    return ret;
+ done:
+   if (out != NULL && *out == NULL)
+       *out = ret;
+   return ret;
+
+ err:
+    if (out == NULL || *out != ret)
+        ASN1_GENERALIZEDTIME_free(ret);
+    return NULL;
 }
 
+
 int ASN1_TIME_set_string(ASN1_TIME *s, const char *str)
 {
     ASN1_TIME t;