gpg: Allow predefined names as answer to the keygen.algo prompt.

* g10/keygen.c (ask_algo): Add list of strings.

--
Signed-off-by: Werner Koch <wk@gnupg.org>
(backported from commit b1d5ed6ac842469afcb84868d0f6641dc286a6c7)

doc/DETAILS

@@ -1301,3 +1301,31 @@ This can be implemented using Hurd's translator mechanism.
 However, I think the whole key server stuff has to be re-thought;
 I have some ideas and probably create a white paper.
 
+
+Algorithm names for the "keygen.algo" prompt
+============================================
+
+  When using a --command-fd controlled key generation or "addkey"
+  there is way to know the number to enter on the "keygen.algo"
+  prompt.  The displayed numbers are for human reception and may
+  change with releases.  To provide a stable way to enter a desired
+  algorithm choice the prompt also accepts predefined names for the
+  algorithms, which will not change.
+
+   | Name    | No | Description                     |
+   |---------+----+---------------------------------|
+   | rsa+rsa |  1 | RSA and RSA (default)           |
+   | dsa+elg |  2 | DSA and Elgamal                 |
+   | dsa     |  3 | DSA (sign only)                 |
+   | rsa/s   |  4 | RSA (sign only)                 |
+   | elg     |  5 | Elgamal (encrypt only)          |
+   | rsa/e   |  6 | RSA (encrypt only)              |
+   | dsa/*   |  7 | DSA (set your own capabilities) |
+   | rsa/*   |  8 | RSA (set your own capabilities) |
+
+   If one of the "foo/*" names are used a "keygen.flags" prompt needs
+   to be answered as well.  Instead of toggling the predefined flags,
+   it is also possible to set them direct: Use a "=" character
+   directly followed by a comination of "a" (for authentication), "s"
+   (for signing), or "c" (for certification).
+

g10/keygen.c

@@ -1700,7 +1700,7 @@ ask_key_flags(int algo,int subkey)
 static int
 ask_algo (int addmode, int *r_subkey_algo, unsigned int *r_usage)
 {
-  char *answer;
+  char *answer = NULL;
   int algo;
   int dummy_algo;
 
@@ -1732,53 +1732,53 @@ ask_algo (int addmode, int *r_subkey_algo, unsigned int *r_usage)
     {
       *r_usage = 0;
       *r_subkey_algo = 0;
+      xfree (answer);
       answer = cpr_get ("keygen.algo", _("Your selection? "));
       cpr_kill_prompt ();
       algo = *answer? atoi (answer) : 1;
-      xfree(answer);
+      if ((algo == 1 || !strcmp (answer, "rsa+rsa")) && !addmode)
-      if (algo == 1 && !addmode)
         {
           algo = PUBKEY_ALGO_RSA;
           *r_subkey_algo = PUBKEY_ALGO_RSA;
           break;
 	}
-      else if (algo == 2 && !addmode)
+      else if ((algo == 2 || !strcmp (answer, "dsa+elg")) && !addmode)
         {
           algo = PUBKEY_ALGO_DSA;
           *r_subkey_algo = PUBKEY_ALGO_ELGAMAL_E;
           break;
 	}
-      else if (algo == 3)
+      else if (algo == 3 || !strcmp (answer, "dsa"))
         {
           algo = PUBKEY_ALGO_DSA;
           *r_usage = PUBKEY_USAGE_SIG;
           break;
 	}
-      else if (algo == 4)
+      else if (algo == 4 || !strcmp (answer, "rsa/s"))
         {
           algo = PUBKEY_ALGO_RSA;
           *r_usage = PUBKEY_USAGE_SIG;
           break;
 	}
-      else if (algo == 5 && addmode)
+      else if ((algo == 5 || !strcmp (answer, "elg")) && addmode)
         {
           algo = PUBKEY_ALGO_ELGAMAL_E;
           *r_usage = PUBKEY_USAGE_ENC;
           break;
 	}
-      else if (algo == 6 && addmode)
+      else if ((algo == 6 || !strcmp (answer, "rsa/e")) && addmode)
         {
           algo = PUBKEY_ALGO_RSA;
           *r_usage = PUBKEY_USAGE_ENC;
           break;
 	}
-      else if (algo == 7 && opt.expert)
+      else if ((algo == 7 || !strcmp (answer, "dsa/*")) && opt.expert)
         {
           algo = PUBKEY_ALGO_DSA;
           *r_usage = ask_key_flags (algo, addmode);
           break;
 	}
-      else if (algo == 8 && opt.expert)
+      else if ((algo == 8 || !strcmp (answer, "rsa/*")) && opt.expert)
         {
           algo = PUBKEY_ALGO_RSA;
           *r_usage = ask_key_flags (algo, addmode);
@@ -1786,8 +1786,10 @@ ask_algo (int addmode, int *r_subkey_algo, unsigned int *r_usage)
 	}
       else
         tty_printf (_("Invalid selection.\n"));
+
     }
 
+  xfree(answer);
   return algo;
 }