conn: add 'attach' to protocol handler, make libssh2 use it

The libssh2 backend has SSH session associated with the connection but
the callback context is the easy handle, so when a connection gets
attached to a transfer, the protocol handler now allows for a custom
function to get used to set things up correctly.

Reported-by: Michael O'Farrell
Fixes #6898
Closes #7078

24 files changed, 66 insertions, 0 deletions

diff --git a/lib/curl_rtmp.c b/lib/curl_rtmp.c
index 1360f335f..2fa026796 100644
--- a/lib/curl_rtmp.c
+++ b/lib/curl_rtmp.c
@@ -79,6 +79,7 @@ const struct Curl_handler Curl_handler_rtmp = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMP,                            /* defport */
   CURLPROTO_RTMP,                       /* protocol */
   CURLPROTO_RTMP,                       /* family */
@@ -101,6 +102,7 @@ const struct Curl_handler Curl_handler_rtmpt = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMPT,                           /* defport */
   CURLPROTO_RTMPT,                      /* protocol */
   CURLPROTO_RTMPT,                      /* family */
@@ -123,6 +125,7 @@ const struct Curl_handler Curl_handler_rtmpe = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMP,                            /* defport */
   CURLPROTO_RTMPE,                      /* protocol */
   CURLPROTO_RTMPE,                      /* family */
@@ -145,6 +148,7 @@ const struct Curl_handler Curl_handler_rtmpte = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMPT,                           /* defport */
   CURLPROTO_RTMPTE,                     /* protocol */
   CURLPROTO_RTMPTE,                     /* family */
@@ -167,6 +171,7 @@ const struct Curl_handler Curl_handler_rtmps = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMPS,                           /* defport */
   CURLPROTO_RTMPS,                      /* protocol */
   CURLPROTO_RTMP,                       /* family */
@@ -189,6 +194,7 @@ const struct Curl_handler Curl_handler_rtmpts = {
   rtmp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTMPS,                           /* defport */
   CURLPROTO_RTMPTS,                     /* protocol */
   CURLPROTO_RTMPT,                      /* family */
diff --git a/lib/dict.c b/lib/dict.c
index 666fb374c..625b05777 100644
--- a/lib/dict.c
+++ b/lib/dict.c
@@ -89,6 +89,7 @@ const struct Curl_handler Curl_handler_dict = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_DICT,                            /* defport */
   CURLPROTO_DICT,                       /* protocol */
   CURLPROTO_DICT,                       /* family */
diff --git a/lib/file.c b/lib/file.c
index e54406699..0420db345 100644
--- a/lib/file.c
+++ b/lib/file.c
@@ -111,6 +111,7 @@ const struct Curl_handler Curl_handler_file = {
   file_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   0,                                    /* defport */
   CURLPROTO_FILE,                       /* protocol */
   CURLPROTO_FILE,                       /* family */
diff --git a/lib/ftp.c b/lib/ftp.c
index 463ddd5b2..444cf35f5 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -175,6 +175,7 @@ const struct Curl_handler Curl_handler_ftp = {
   ftp_disconnect,                  /* disconnect */
   ZERO_NULL,                       /* readwrite */
   ZERO_NULL,                       /* connection_check */
+  ZERO_NULL,                       /* attach connection */
   PORT_FTP,                        /* defport */
   CURLPROTO_FTP,                   /* protocol */
   CURLPROTO_FTP,                   /* family */
@@ -205,6 +206,7 @@ const struct Curl_handler Curl_handler_ftps = {
   ftp_disconnect,                  /* disconnect */
   ZERO_NULL,                       /* readwrite */
   ZERO_NULL,                       /* connection_check */
+  ZERO_NULL,                       /* attach connection */
   PORT_FTPS,                       /* defport */
   CURLPROTO_FTPS,                  /* protocol */
   CURLPROTO_FTP,                   /* family */
diff --git a/lib/gopher.c b/lib/gopher.c
index a39cc7e6b..f61232ff5 100644
--- a/lib/gopher.c
+++ b/lib/gopher.c
@@ -74,6 +74,7 @@ const struct Curl_handler Curl_handler_gopher = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_GOPHER,                          /* defport */
   CURLPROTO_GOPHER,                     /* protocol */
   CURLPROTO_GOPHER,                     /* family */
@@ -97,6 +98,7 @@ const struct Curl_handler Curl_handler_gophers = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_GOPHER,                          /* defport */
   CURLPROTO_GOPHERS,                    /* protocol */
   CURLPROTO_GOPHER,                     /* family */
diff --git a/lib/http.c b/lib/http.c
index ef71546b7..628dd7370 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -133,6 +133,7 @@ const struct Curl_handler Curl_handler_http = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_HTTP,                            /* defport */
   CURLPROTO_HTTP,                       /* protocol */
   CURLPROTO_HTTP,                       /* family */
@@ -160,6 +161,7 @@ const struct Curl_handler Curl_handler_https = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_HTTPS,                           /* defport */
   CURLPROTO_HTTPS,                      /* protocol */
   CURLPROTO_HTTP,                       /* family */
diff --git a/lib/http2.c b/lib/http2.c
index bc604ce15..f194c18b2 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -319,6 +319,7 @@ static const struct Curl_handler Curl_handler_http2 = {
   http2_disconnect,                     /* disconnect */
   ZERO_NULL,                            /* readwrite */
   http2_conncheck,                      /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_HTTP,                            /* defport */
   CURLPROTO_HTTP,                       /* protocol */
   CURLPROTO_HTTP,                       /* family */
@@ -341,6 +342,7 @@ static const struct Curl_handler Curl_handler_http2_ssl = {
   http2_disconnect,                     /* disconnect */
   ZERO_NULL,                            /* readwrite */
   http2_conncheck,                      /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_HTTP,                            /* defport */
   CURLPROTO_HTTPS,                      /* protocol */
   CURLPROTO_HTTP,                       /* family */
diff --git a/lib/imap.c b/lib/imap.c
index f2bb8aa1f..d85bcc391 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -136,6 +136,7 @@ const struct Curl_handler Curl_handler_imap = {
   imap_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_IMAP,                        /* defport */
   CURLPROTO_IMAP,                   /* protocol */
   CURLPROTO_IMAP,                   /* family */
@@ -164,6 +165,7 @@ const struct Curl_handler Curl_handler_imaps = {
   imap_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_IMAPS,                       /* defport */
   CURLPROTO_IMAPS,                  /* protocol */
   CURLPROTO_IMAP,                   /* family */
diff --git a/lib/ldap.c b/lib/ldap.c
index 2f1032285..ed1642302 100644
--- a/lib/ldap.c
+++ b/lib/ldap.c
@@ -149,6 +149,7 @@ const struct Curl_handler Curl_handler_ldap = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_LDAP,                            /* defport */
   CURLPROTO_LDAP,                       /* protocol */
   CURLPROTO_LDAP,                       /* family */
@@ -176,6 +177,7 @@ const struct Curl_handler Curl_handler_ldaps = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_LDAPS,                           /* defport */
   CURLPROTO_LDAPS,                      /* protocol */
   CURLPROTO_LDAP,                       /* family */
diff --git a/lib/mqtt.c b/lib/mqtt.c
index 2134409cd..d88fa737d 100644
--- a/lib/mqtt.c
+++ b/lib/mqtt.c
@@ -86,6 +86,7 @@ const struct Curl_handler Curl_handler_mqtt = {
   ZERO_NULL,                          /* disconnect */
   ZERO_NULL,                          /* readwrite */
   ZERO_NULL,                          /* connection_check */
+  ZERO_NULL,                          /* attach connection */
   PORT_MQTT,                          /* defport */
   CURLPROTO_MQTT,                     /* protocol */
   CURLPROTO_MQTT,                     /* family */
diff --git a/lib/multi.c b/lib/multi.c
index f7b1da9ab..54365f399 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -896,6 +896,8 @@ void Curl_attach_connnection(struct Curl_easy *data,
   data->conn = conn;
   Curl_llist_insert_next(&conn->easyq, conn->easyq.tail, data,
                          &data->conn_queue);
+  if(conn->handler->attach)
+    conn->handler->attach(data, conn);
 }
 
 static int waitconnect_getsock(struct connectdata *conn,
diff --git a/lib/openldap.c b/lib/openldap.c
index 20d4f51a6..0b8bc34a0 100644
--- a/lib/openldap.c
+++ b/lib/openldap.c
@@ -107,6 +107,7 @@ const struct Curl_handler Curl_handler_ldap = {
   oldap_disconnect,                     /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_LDAP,                            /* defport */
   CURLPROTO_LDAP,                       /* protocol */
   CURLPROTO_LDAP,                       /* family */
@@ -134,6 +135,7 @@ const struct Curl_handler Curl_handler_ldaps = {
   oldap_disconnect,                     /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_LDAPS,                           /* defport */
   CURLPROTO_LDAPS,                      /* protocol */
   CURLPROTO_LDAP,                       /* family */
diff --git a/lib/pop3.c b/lib/pop3.c
index 19ea0e678..9b6ea6480 100644
--- a/lib/pop3.c
+++ b/lib/pop3.c
@@ -131,6 +131,7 @@ const struct Curl_handler Curl_handler_pop3 = {
   pop3_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_POP3,                        /* defport */
   CURLPROTO_POP3,                   /* protocol */
   CURLPROTO_POP3,                   /* family */
@@ -159,6 +160,7 @@ const struct Curl_handler Curl_handler_pop3s = {
   pop3_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_POP3S,                       /* defport */
   CURLPROTO_POP3S,                  /* protocol */
   CURLPROTO_POP3,                   /* family */
diff --git a/lib/rtsp.c b/lib/rtsp.c
index bc7511984..007d5c50b 100644
--- a/lib/rtsp.c
+++ b/lib/rtsp.c
@@ -109,6 +109,7 @@ const struct Curl_handler Curl_handler_rtsp = {
   rtsp_disconnect,                      /* disconnect */
   rtsp_rtp_readwrite,                   /* readwrite */
   rtsp_conncheck,                       /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_RTSP,                            /* defport */
   CURLPROTO_RTSP,                       /* protocol */
   CURLPROTO_RTSP,                       /* family */
diff --git a/lib/smb.c b/lib/smb.c
index 0bf595ca0..39facb267 100644
--- a/lib/smb.c
+++ b/lib/smb.c
@@ -88,6 +88,7 @@ const struct Curl_handler Curl_handler_smb = {
   smb_disconnect,                       /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_SMB,                             /* defport */
   CURLPROTO_SMB,                        /* protocol */
   CURLPROTO_SMB,                        /* family */
@@ -114,6 +115,7 @@ const struct Curl_handler Curl_handler_smbs = {
   smb_disconnect,                       /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_SMBS,                            /* defport */
   CURLPROTO_SMBS,                       /* protocol */
   CURLPROTO_SMB,                        /* family */
diff --git a/lib/smtp.c b/lib/smtp.c
index d6f9b17c5..feffc05bc 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -136,6 +136,7 @@ const struct Curl_handler Curl_handler_smtp = {
   smtp_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_SMTP,                        /* defport */
   CURLPROTO_SMTP,                   /* protocol */
   CURLPROTO_SMTP,                   /* family */
@@ -164,6 +165,7 @@ const struct Curl_handler Curl_handler_smtps = {
   smtp_disconnect,                  /* disconnect */
   ZERO_NULL,                        /* readwrite */
   ZERO_NULL,                        /* connection_check */
+  ZERO_NULL,                        /* attach connection */
   PORT_SMTPS,                       /* defport */
   CURLPROTO_SMTPS,                  /* protocol */
   CURLPROTO_SMTP,                   /* family */
diff --git a/lib/telnet.c b/lib/telnet.c
index f96a4cb4c..26e0658ba 100644
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -185,6 +185,7 @@ const struct Curl_handler Curl_handler_telnet = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_TELNET,                          /* defport */
   CURLPROTO_TELNET,                     /* protocol */
   CURLPROTO_TELNET,                     /* family */
diff --git a/lib/tftp.c b/lib/tftp.c
index ffd7e8a6d..11150af36 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -182,6 +182,7 @@ const struct Curl_handler Curl_handler_tftp = {
   tftp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_TFTP,                            /* defport */
   CURLPROTO_TFTP,                       /* protocol */
   CURLPROTO_TFTP,                       /* family */
diff --git a/lib/url.c b/lib/url.c
index 74ebb6f91..5f6462617 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -292,6 +292,7 @@ static const struct Curl_handler Curl_handler_dummy = {
   ZERO_NULL,                            /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   0,                                    /* defport */
   0,                                    /* protocol */
   0,                                    /* family */
diff --git a/lib/urldata.h b/lib/urldata.h
index 707e91f8e..fb905c36c 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -794,12 +794,16 @@ struct Curl_handler {
                                    struct connectdata *conn,
                                    unsigned int checks_to_perform);
 
+  /* attach() attaches this transfer to this connection */
+  void (*attach)(struct Curl_easy *data, struct connectdata *conn);
+
   int defport;            /* Default port. */
   unsigned int protocol;  /* See CURLPROTO_* - this needs to be the single
                              specific protocol bit */
   unsigned int family;    /* single bit for protocol family; basically the
                              non-TLS name of the protocol this is */
   unsigned int flags;     /* Extra particular characteristics, see PROTOPT_* */
+
 };
 
 #define PROTOPT_NONE 0             /* nothing extra */
diff --git a/lib/vssh/libssh.c b/lib/vssh/libssh.c
index 59084f6c1..d146d15fd 100644
--- a/lib/vssh/libssh.c
+++ b/lib/vssh/libssh.c
@@ -159,6 +159,7 @@ const struct Curl_handler Curl_handler_scp = {
   scp_disconnect,               /* disconnect */
   ZERO_NULL,                    /* readwrite */
   ZERO_NULL,                    /* connection_check */
+  ZERO_NULL,                    /* attach connection */
   PORT_SSH,                     /* defport */
   CURLPROTO_SCP,                /* protocol */
   CURLPROTO_SCP,                /* family */
@@ -185,6 +186,7 @@ const struct Curl_handler Curl_handler_sftp = {
   sftp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_SSH,                             /* defport */
   CURLPROTO_SFTP,                       /* protocol */
   CURLPROTO_SFTP,                       /* family */
diff --git a/lib/vssh/libssh2.c b/lib/vssh/libssh2.c
index c39870387..8a6345b94 100644
--- a/lib/vssh/libssh2.c
+++ b/lib/vssh/libssh2.c
@@ -121,6 +121,7 @@ static int ssh_getsock(struct Curl_easy *data, struct connectdata *conn,
                        curl_socket_t *sock);
 static CURLcode ssh_setup_connection(struct Curl_easy *data,
                                      struct connectdata *conn);
+static void ssh_attach(struct Curl_easy *data, struct connectdata *conn);
 
 /*
  * SCP protocol handler.
@@ -142,6 +143,7 @@ const struct Curl_handler Curl_handler_scp = {
   scp_disconnect,                       /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ssh_attach,
   PORT_SSH,                             /* defport */
   CURLPROTO_SCP,                        /* protocol */
   CURLPROTO_SCP,                        /* family */
@@ -170,6 +172,7 @@ const struct Curl_handler Curl_handler_sftp = {
   sftp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ssh_attach,
   PORT_SSH,                             /* defport */
   CURLPROTO_SFTP,                       /* protocol */
   CURLPROTO_SFTP,                       /* family */
@@ -3604,4 +3607,21 @@ size_t Curl_ssh_version(char *buffer, size_t buflen)
   return msnprintf(buffer, buflen, "libssh2/%s", LIBSSH2_VERSION);
 }
 
+/* The SSH session is associated with the *CONNECTION* but the callback user
+ * pointer is an easy handle pointer. This function allows us to reassign the
+ * user pointer to the *CURRENT* (new) easy handle.
+ */
+static void ssh_attach(struct Curl_easy *data, struct connectdata *conn)
+{
+  DEBUGASSERT(data);
+  DEBUGASSERT(conn);
+  if(conn->handler->protocol & PROTO_FAMILY_SSH) {
+    struct ssh_conn *sshc = &conn->proto.sshc;
+    if(sshc->ssh_session) {
+      /* only re-attach if the session already exists */
+      void **abstract = libssh2_session_abstract(sshc->ssh_session);
+      *abstract = data;
+    }
+  }
+}
 #endif /* USE_LIBSSH2 */
diff --git a/lib/vssh/ssh.h b/lib/vssh/ssh.h
index 52e1ee6c2..505b0787c 100644
--- a/lib/vssh/ssh.h
+++ b/lib/vssh/ssh.h
@@ -263,9 +263,12 @@ extern const struct Curl_handler Curl_handler_sftp;
 CURLcode Curl_ssh_init(void);
 void Curl_ssh_cleanup(void);
 size_t Curl_ssh_version(char *buffer, size_t buflen);
+void Curl_ssh_attach(struct Curl_easy *data,
+                     struct connectdata *conn);
 #else
 /* for non-SSH builds */
 #define Curl_ssh_cleanup()
+#define Curl_ssh_attach(x,y)
 #endif
 
 #endif /* HEADER_CURL_SSH_H */
diff --git a/lib/vssh/wolfssh.c b/lib/vssh/wolfssh.c
index 487b30ce4..9f3266a24 100644
--- a/lib/vssh/wolfssh.c
+++ b/lib/vssh/wolfssh.c
@@ -91,6 +91,7 @@ const struct Curl_handler Curl_handler_scp = {
   wscp_disconnect,                      /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_SSH,                             /* defport */
   CURLPROTO_SCP,                        /* protocol */
   PROTOPT_DIRLOCK | PROTOPT_CLOSEACTION
@@ -119,6 +120,7 @@ const struct Curl_handler Curl_handler_sftp = {
   wsftp_disconnect,                     /* disconnect */
   ZERO_NULL,                            /* readwrite */
   ZERO_NULL,                            /* connection_check */
+  ZERO_NULL,                            /* attach connection */
   PORT_SSH,                             /* defport */
   CURLPROTO_SFTP,                       /* protocol */
   CURLPROTO_SFTP,                       /* family */