Add an IV argument to aes_{en,de}crypt_pubkey.

No functional change: currently, the IV passed in is always zero
(except in the test suite). But this prepares to change that in a
future revision of the key file format.

ssh.h

@@ -1321,8 +1321,10 @@ void des3_decrypt_pubkey_ossh(const void *key, const void *iv,
                               void *blk, int len);
 void des3_encrypt_pubkey_ossh(const void *key, const void *iv,
                               void *blk, int len);
-void aes256_encrypt_pubkey(const void *key, void *blk, int len);
-void aes256_decrypt_pubkey(const void *key, void *blk, int len);
+void aes256_encrypt_pubkey(const void *key, const void *iv,
+                           void *blk, int len);
+void aes256_decrypt_pubkey(const void *key, const void *iv,
+                           void *blk, int len);
 
 void des_encrypt_xdmauth(const void *key, void *blk, int len);
 void des_decrypt_xdmauth(const void *key, void *blk, int len);

sshauxcrypt.c

@@ -11,30 +11,28 @@
 
 #include "ssh.h"
 
-static ssh_cipher *aes256_pubkey_cipher(const void *key)
+static ssh_cipher *aes256_pubkey_cipher(const void *key, const void *iv)
 {
     /*
      * PuTTY's own .PPK format for SSH-2 private key files is
      * encrypted with 256-bit AES in CBC mode.
      */
-    char iv[16];
-    memset(iv, 0, 16);
     ssh_cipher *cipher = ssh_cipher_new(&ssh_aes256_cbc);
     ssh_cipher_setkey(cipher, key);
     ssh_cipher_setiv(cipher, iv);
     return cipher;
 }
 
-void aes256_encrypt_pubkey(const void *key, void *blk, int len)
+void aes256_encrypt_pubkey(const void *key, const void *iv, void *blk, int len)
 {
-    ssh_cipher *c = aes256_pubkey_cipher(key);
+    ssh_cipher *c = aes256_pubkey_cipher(key, iv);
     ssh_cipher_encrypt(c, blk, len);
     ssh_cipher_free(c);
 }
 
-void aes256_decrypt_pubkey(const void *key, void *blk, int len)
+void aes256_decrypt_pubkey(const void *key, const void *iv, void *blk, int len)
 {
-    ssh_cipher *c = aes256_pubkey_cipher(key);
+    ssh_cipher *c = aes256_pubkey_cipher(key, iv);
     ssh_cipher_decrypt(c, blk, len);
     ssh_cipher_free(c);
 }

sshpubk.c

@@ -608,6 +608,8 @@ static int userkey_parse_line_counter(const char *text)
         return -1;
 }
 
+static const unsigned char zero_iv[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+
 ssh2_userkey *ppk_load_s(BinarySource *src, const char *passphrase,
                          const char **errorstr)
 {
@@ -729,7 +731,8 @@ ssh2_userkey *ppk_load_s(BinarySource *src, const char *passphrase,
             goto error;
 
         ssh2_ppk_derivekey(ptrlen_from_asciz(passphrase), key);
-        aes256_decrypt_pubkey(key, private_blob->u, private_blob->len);
+        aes256_decrypt_pubkey(key, zero_iv,
+                              private_blob->u, private_blob->len);
     }
 
     /*
@@ -1323,7 +1326,8 @@ strbuf *ppk_save_sb(ssh2_userkey *key, const char *passphrase)
         unsigned char key[40];
 
         ssh2_ppk_derivekey(ptrlen_from_asciz(passphrase), key);
-        aes256_encrypt_pubkey(key, priv_blob_encrypted, priv_encrypted_len);
+        aes256_encrypt_pubkey(key, zero_iv,
+                              priv_blob_encrypted, priv_encrypted_len);
 
         smemclr(key, sizeof(key));
     }

test/cryptsuite.py

@@ -1410,11 +1410,20 @@ class crypt(MyTestBase):
         p = b'three AES blocks, or six DES, of arbitrary input'
 
         k = b'thirty-two-byte aes-256 test key'
+        iv = b'\0' * 16
         c = unhex('7b112d00c0fc95bc13fcdacfd43281bf'
                   'de9389db1bbcfde79d59a303d41fd2eb'
                   '0955c9477ae4ee3a4d6c1fbe474c0ef6')
-        self.assertEqualBin(aes256_encrypt_pubkey(k, p), c)
-        self.assertEqualBin(aes256_decrypt_pubkey(k, c), p)
+        self.assertEqualBin(aes256_encrypt_pubkey(k, iv, p), c)
+        self.assertEqualBin(aes256_decrypt_pubkey(k, iv, c), p)
+
+        # same k as in the previous case
+        iv = unhex('0102030405060708090a0b0c0d0e0f10')
+        c = unhex('9e9c8a91b739677b834397bdd8e70c05'
+                  'c3e2cf6cce68d376d798a59848621c6d'
+                  '42b9e7101260a438daadd7b742875a36')
+        self.assertEqualBin(aes256_encrypt_pubkey(k, iv, p), c)
+        self.assertEqualBin(aes256_decrypt_pubkey(k, iv, c), p)
 
         k = b'3des with keys distinct.'
         iv = b'randomIV'

testcrypt.c

@@ -1029,28 +1029,32 @@ strbuf *des3_decrypt_pubkey_ossh_wrapper(ptrlen key, ptrlen iv, ptrlen data)
 }
 #define des3_decrypt_pubkey_ossh des3_decrypt_pubkey_ossh_wrapper
 
-strbuf *aes256_encrypt_pubkey_wrapper(ptrlen key, ptrlen data)
+strbuf *aes256_encrypt_pubkey_wrapper(ptrlen key, ptrlen iv, ptrlen data)
 {
     if (key.len != 32)
         fatal_error("aes256_encrypt_pubkey: key must be 32 bytes long");
+    if (iv.len != 16)
+        fatal_error("aes256_encrypt_pubkey: iv must be 16 bytes long");
     if (data.len % 16 != 0)
         fatal_error("aes256_encrypt_pubkey: data must be a multiple of 16 bytes");
     strbuf *sb = strbuf_new();
     put_datapl(sb, data);
-    aes256_encrypt_pubkey(key.ptr, sb->u, sb->len);
+    aes256_encrypt_pubkey(key.ptr, iv.ptr, sb->u, sb->len);
     return sb;
 }
 #define aes256_encrypt_pubkey aes256_encrypt_pubkey_wrapper
 
-strbuf *aes256_decrypt_pubkey_wrapper(ptrlen key, ptrlen data)
+strbuf *aes256_decrypt_pubkey_wrapper(ptrlen key, ptrlen iv, ptrlen data)
 {
     if (key.len != 32)
         fatal_error("aes256_decrypt_pubkey: key must be 32 bytes long");
+    if (iv.len != 16)
+        fatal_error("aes256_encrypt_pubkey: iv must be 16 bytes long");
     if (data.len % 16 != 0)
         fatal_error("aes256_decrypt_pubkey: data must be a multiple of 16 bytes");
     strbuf *sb = strbuf_new();
     put_datapl(sb, data);
-    aes256_decrypt_pubkey(key.ptr, sb->u, sb->len);
+    aes256_decrypt_pubkey(key.ptr, iv.ptr, sb->u, sb->len);
     return sb;
 }
 #define aes256_decrypt_pubkey aes256_decrypt_pubkey_wrapper

testcrypt.h

@@ -299,8 +299,8 @@ FUNC2(val_string, des3_encrypt_pubkey, val_string_ptrlen, val_string_ptrlen)
 FUNC2(val_string, des3_decrypt_pubkey, val_string_ptrlen, val_string_ptrlen)
 FUNC3(val_string, des3_encrypt_pubkey_ossh, val_string_ptrlen, val_string_ptrlen, val_string_ptrlen)
 FUNC3(val_string, des3_decrypt_pubkey_ossh, val_string_ptrlen, val_string_ptrlen, val_string_ptrlen)
-FUNC2(val_string, aes256_encrypt_pubkey, val_string_ptrlen, val_string_ptrlen)
-FUNC2(val_string, aes256_decrypt_pubkey, val_string_ptrlen, val_string_ptrlen)
+FUNC3(val_string, aes256_encrypt_pubkey, val_string_ptrlen, val_string_ptrlen, val_string_ptrlen)
+FUNC3(val_string, aes256_decrypt_pubkey, val_string_ptrlen, val_string_ptrlen, val_string_ptrlen)
 FUNC1(uint, crc32_rfc1662, val_string_ptrlen)
 FUNC1(uint, crc32_ssh1, val_string_ptrlen)
 FUNC2(uint, crc32_update, uint, val_string_ptrlen)