Rewrite SSH key loading and saving using marshal.h.

All the functions that read and write public and private keys to a
FILE * are now small wrappers on top of an underlying set of functions
that read data in the same format from a BinarySource, or write it to
a strbuf. This sets me up to deal with key files in contexts other
than on disk.

ssh.h

@@ -1165,19 +1165,33 @@ extern void base64_encode(FILE *fp, const unsigned char *data, int datalen,
 extern ssh2_userkey ssh2_wrong_passphrase;
 #define SSH2_WRONG_PASSPHRASE (&ssh2_wrong_passphrase)
 
+bool ppk_encrypted_s(BinarySource *src, char **comment);
 bool ppk_encrypted_f(const Filename *filename, char **comment);
+bool rsa1_encrypted_s(BinarySource *src, char **comment);
 bool rsa1_encrypted_f(const Filename *filename, char **comment);
 
+ssh2_userkey *ppk_load_s(BinarySource *src, const char *passphrase,
+                         const char **errorstr);
 ssh2_userkey *ppk_load_f(const Filename *filename, const char *passphrase,
                          const char **errorstr);
+int rsa1_load_s(BinarySource *src, RSAKey *key,
+                const char *passphrase, const char **errorstr);
 int rsa1_load_f(const Filename *filename, RSAKey *key,
                 const char *passphrase, const char **errorstr);
 
-bool ppk_save_f(const Filename *filename, ssh2_userkey *key, char *passphrase);
-bool rsa1_save_f(const Filename *filename, RSAKey *key, char *passphrase);
+strbuf *ppk_save_sb(ssh2_userkey *key, const char *passphrase);
+bool ppk_save_f(const Filename *filename, ssh2_userkey *key,
+                const char *passphrase);
+strbuf *rsa1_save_sb(RSAKey *key, const char *passphrase);
+bool rsa1_save_f(const Filename *filename, RSAKey *key,
+                 const char *passphrase);
 
+bool ppk_loadpub_s(BinarySource *src, char **algorithm, BinarySink *bs,
+                   char **commentptr, const char **errorstr);
 bool ppk_loadpub_f(const Filename *filename, char **algorithm, BinarySink *bs,
                    char **commentptr, const char **errorstr);
+int rsa1_loadpub_s(BinarySource *src, BinarySink *bs,
+                   char **commentptr, const char **errorstr);
 int rsa1_loadpub_f(const Filename *filename, BinarySink *bs,
                    char **commentptr, const char **errorstr);