From 6b303169225f9e3ce62dd90445be61865af9b104 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Sat, 2 May 2015 15:11:41 +0100
Subject: [PATCH] Use find_pubkey_alg in openssh_read_new().

This is better than listing all the algorithm names in yet another
place that will then need updating when a new key format is added.
However, that also means I need to find a new place to put the
'npieces' value I was previously setting up differently per key type;
since that's a fundamental property of the key format, I've moved it
to a constant field in the ssh_signkey structure, and filled that
field in for all the existing key types with the values from the
replaced code in openssh_read_new().
---
 import.c | 34 ++++++++++++----------------------
 ssh.h    |  9 +++++++++
 sshdss.c |  1 +
 sshecc.c |  3 +++
 sshrsa.c |  1 +
 5 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/import.c b/import.c
index 6206fdb1..92141d3a 100644
--- a/import.c
+++ b/import.c
@@ -1629,7 +1629,7 @@ struct ssh2_userkey *openssh_new_read(const Filename *filename,
     retkey = NULL;
     for (key_index = 0; key_index < key->nkeys; key_index++) {
         unsigned char *thiskey;
-        int thiskeylen, npieces;
+        int thiskeylen;
 
         /*
          * Read the key type, which will tell us how to scan over
@@ -1647,26 +1647,16 @@ struct ssh2_userkey *openssh_new_read(const Filename *filename,
          * of strings, so we just need to know how many of them to
          * skip over. (The numbers below exclude the key comment.)
          */
-        if (match_ssh_id(stringlen, string, "ssh-rsa")) {
-            alg = &ssh_rsa;
-            npieces = 6;           /* n,e,d,iqmp,q,p */
-        } else if (match_ssh_id(stringlen, string, "ssh-dss")) {
-            alg = &ssh_dss;
-            npieces = 5;           /* p,q,g,y,x */
-        } else if (match_ssh_id(stringlen, string,
-                                "ecdsa-sha2-nistp256")) {
-            alg = &ssh_ecdsa_nistp256;
-            npieces = 3;      /* curve name, point, private exponent */
-        } else if (match_ssh_id(stringlen, string,
-                                "ecdsa-sha2-nistp384")) {
-            alg = &ssh_ecdsa_nistp384;
-            npieces = 3;      /* curve name, point, private exponent */
-        } else if (match_ssh_id(stringlen, string,
-                                "ecdsa-sha2-nistp521")) {
-            alg = &ssh_ecdsa_nistp521;
-            npieces = 3;      /* curve name, point, private exponent */
-        } else {
-            errmsg = "private key did not start with type string\n";
+        {
+            /* find_pubkey_alg needs a zero-terminated copy of the
+             * algorithm name */
+            char *name_zt = dupprintf("%.*s", stringlen, (char *)string);
+            alg = find_pubkey_alg(name_zt);
+            sfree(name_zt);
+        }
+
+        if (!alg) {
+            errmsg = "private key type not recognised\n";
             goto error;
         }
 
@@ -1675,7 +1665,7 @@ struct ssh2_userkey *openssh_new_read(const Filename *filename,
         /*
          * Skip over the pieces of key.
          */
-        for (i = 0; i < npieces; i++) {
+        for (i = 0; i < alg->openssh_private_npieces; i++) {
             if (!(string = get_ssh_string(&privlen, &priv, &stringlen))) {
                 errmsg = "ran out of data in mid-private-key";
                 goto error;
diff --git a/ssh.h b/ssh.h
index f81d95c5..b733ffa0 100644
--- a/ssh.h
+++ b/ssh.h
@@ -333,6 +333,15 @@ struct ssh_signkey {
 			unsigned char *priv_blob, int priv_len);
     void *(*openssh_createkey) (unsigned char **blob, int *len);
     int (*openssh_fmtkey) (void *key, unsigned char *blob, int len);
+    /* OpenSSH private key blobs, as created by openssh_fmtkey and
+     * consumed by openssh_createkey, always (at least so far...) take
+     * the form of a number of SSH-2 strings / mpints concatenated
+     * end-to-end. Because the new-style OpenSSH private key format
+     * stores those blobs without a containing string wrapper, we need
+     * to know how many strings each one consists of, so that we can
+     * skip over the right number to find the next key in the file.
+     * openssh_private_npieces gives that information. */
+    int openssh_private_npieces;
     int (*pubkey_bits) (void *blob, int len);
     char *(*fingerprint) (void *key);
     int (*verifysig) (void *key, char *sig, int siglen,
diff --git a/sshdss.c b/sshdss.c
index 3682ad69..40285a02 100644
--- a/sshdss.c
+++ b/sshdss.c
@@ -701,6 +701,7 @@ const struct ssh_signkey ssh_dss = {
     dss_createkey,
     dss_openssh_createkey,
     dss_openssh_fmtkey,
+    5 /* p,q,g,y,x */,
     dss_pubkey_bits,
     dss_fingerprint,
     dss_verifysig,
diff --git a/sshecc.c b/sshecc.c
index 10c4fc11..9b2e5020 100644
--- a/sshecc.c
+++ b/sshecc.c
@@ -1966,6 +1966,7 @@ const struct ssh_signkey ssh_ecdsa_nistp256 = {
     ecdsa_createkey,
     ecdsa_openssh_createkey,
     ecdsa_openssh_fmtkey,
+    3 /* curve name, point, private exponent */,
     ecdsa_pubkey_bits,
     ecdsa_fingerprint,
     ecdsa_verifysig,
@@ -1983,6 +1984,7 @@ const struct ssh_signkey ssh_ecdsa_nistp384 = {
     ecdsa_createkey,
     ecdsa_openssh_createkey,
     ecdsa_openssh_fmtkey,
+    3 /* curve name, point, private exponent */,
     ecdsa_pubkey_bits,
     ecdsa_fingerprint,
     ecdsa_verifysig,
@@ -2000,6 +2002,7 @@ const struct ssh_signkey ssh_ecdsa_nistp521 = {
     ecdsa_createkey,
     ecdsa_openssh_createkey,
     ecdsa_openssh_fmtkey,
+    3 /* curve name, point, private exponent */,
     ecdsa_pubkey_bits,
     ecdsa_fingerprint,
     ecdsa_verifysig,
diff --git a/sshrsa.c b/sshrsa.c
index 25f9cf7e..058200f4 100644
--- a/sshrsa.c
+++ b/sshrsa.c
@@ -942,6 +942,7 @@ const struct ssh_signkey ssh_rsa = {
     rsa2_createkey,
     rsa2_openssh_createkey,
     rsa2_openssh_fmtkey,
+    6 /* n,e,d,iqmp,q,p */,
     rsa2_pubkey_bits,
     rsa2_fingerprint,
     rsa2_verifysig,