pem_decode_openssh troubles on architectures: s390x, ppc64, sparc64, x32

[karel-m]

Originally reported here https://github.com/DCIT/perl-CryptX/issues/111

[karel-m]

Possible fix from https://bugs.debian.org/1082952

From c912db56833f8357900b1e798f9c0d8d0daa5b46 Mon Sep 17 00:00:00 2001
From: Niko Tyni <ntyni@debian.org>
Date: Tue, 1 Oct 2024 18:28:14 +0000
Subject: [PATCH] Fix SSH RSA key decryption on 64-bit big endian hosts

Bug-Debian: https://bugs.debian.org/1082952
---
 src/ltc/misc/pem/pem_ssh.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/ltc/misc/pem/pem_ssh.c b/src/ltc/misc/pem/pem_ssh.c
index 00ae4480..8114f231 100644
--- a/src/ltc/misc/pem/pem_ssh.c
+++ b/src/ltc/misc/pem/pem_ssh.c
@@ -675,14 +675,18 @@ static int s_decode_header(unsigned char *in, unsigned long *inlen, struct kdf_o
       opts->name = "none";
    } else if (XSTRCMP((char*)kdfname, "bcrypt") == 0) {
       opts->name = "bcrypt";
-      opts->saltlen = sizeof(opts->salt);
+      unsigned long saltlen = sizeof(opts->salt);
       len = kdfoptionslen;
       if ((err = ssh_decode_sequence_multi(kdfoptions, &len,
-                                           LTC_SSHDATA_STRING, opts->salt, &opts->saltlen,
+                                           LTC_SSHDATA_STRING, opts->salt, &saltlen,
                                            LTC_SSHDATA_UINT32, &opts->num_rounds,
                                            LTC_SSHDATA_EOL,    NULL)) != CRYPT_OK) {
          return err;
       }
+      if (saltlen > 0xffffffff) {
+         return CRYPT_INPUT_TOO_LONG;
+      }
+      opts->saltlen = (ulong32) saltlen;
       if (len != kdfoptionslen) {
          return CRYPT_INPUT_TOO_LONG;
       }
-- 
2.45.2