internal: commit a session only once accepted

src/agent.c

@@ -1731,6 +1731,91 @@ int wolfSSH_AGENT_enable(WOLFSSH* ssh, byte isEnabled)
 }
 
 
+int wolfSSH_AGENT_ChannelOpen(WOLFSSH* ssh)
+{
+    WOLFSSH_AGENT_CTX* newAgent = NULL;
+    WOLFSSH_CHANNEL* newChannel = NULL;
+    int ret = WS_SUCCESS;
+    /* wolfSSH_accept() clears only want-read/want-write/auth-pending, so a
+     * WS_BAD_ARGUMENT latched by a poll kills the handshake. */
+    int recordError = 0;
+
+    WLOG_ENTER();
+
+    if (ssh == NULL)
+        ret = WS_SSH_NULL_E;
+    else if (ssh->ctx->side != WOLFSSH_ENDPOINT_SERVER) {
+        /* Server side only. wolfSSH_connect() sets ssh->agent too, so the
+         * checks below would report a channel a client never opened. */
+        ret = WS_BAD_ARGUMENT;
+    }
+    else if (SendAfterDisconnect(ssh)) {
+        /* The session is over, so neither a new open nor the flush of one
+         * queued before the disconnect may go out. RFC 4253 section 11.1.
+         * WS_DISCONNECT is in ssh->error, where the rest of the API puts
+         * it. */
+        ret = WS_FATAL_ERROR;
+    }
+    else if (!ssh->useAgent) {
+        /* Nothing asked for agent forwarding on this session. */
+        ret = WS_BAD_ARGUMENT;
+    }
+    else if (ssh->agent == NULL) {
+        /* Nothing else sets ssh->agent, so a NULL one means "not opened
+         * yet". Idempotent, so a poll cannot open a second channel. */
+        WLOG(WS_LOG_AGENT, "Starting agent channel");
+
+        newAgent = wolfSSH_AGENT_new(ssh->ctx->heap);
+        if (newAgent == NULL)
+            ret = WS_MEMORY_E;
+
+        if (ret == WS_SUCCESS) {
+            newChannel = ChannelNew(ssh, ID_CHANTYPE_AUTH_AGENT,
+                    ssh->ctx->windowSz, ssh->ctx->maxPacketSz);
+            if (newChannel == NULL)
+                ret = WS_MEMORY_E;
+        }
+
+        if (ret == WS_SUCCESS) {
+            recordError = 1;
+            ret = SendChannelOpenSession(ssh, newChannel);
+
+            if (ret < WS_SUCCESS
+                    && ret != WS_WANT_WRITE && ret != WS_WANT_READ) {
+                ChannelDelete(newChannel, ssh->ctx->heap);
+            }
+            else {
+                /* Publish on a queued open too, so a retry takes the
+                 * already-open path rather than opening a second. */
+                ChannelAppend(ssh, newChannel);
+                newAgent->channel = newChannel->channel;
+                ssh->agent = newAgent;
+                newAgent = NULL;
+                if (ssh->ctx->agentCb) {
+                    ssh->ctx->agentCb(WOLFSSH_AGENT_LOCAL_SETUP,
+                            ssh->agentCbCtx);
+                }
+            }
+        }
+
+        if (newAgent != NULL)
+            wolfSSH_AGENT_free(newAgent);
+    }
+    else if (wolfSSH_OutputPending(ssh)) {
+        /* Any queued output, not just this open. Flush it rather than
+         * report a success the peer hasn't seen. */
+        recordError = 1;
+        ret = wolfSSH_SendPacket(ssh);
+    }
+
+    if (recordError)
+        ssh->error = ret;
+
+    WLOG_LEAVE(ret);
+    return ret;
+}
+
+
 int wolfSSH_AGENT_worker(WOLFSSH* ssh)
 {
     int ret = WS_SUCCESS;

src/internal.c

@@ -1672,6 +1672,7 @@ WOLFSSH* SshInit(WOLFSSH* ssh, WOLFSSH_CTX* ctx)
     ssh->highwaterMark = ctx->highwaterMark;
     ssh->msgHighwaterMark = ctx->msgHighwaterMark;
     ssh->maxAuthAttempts = ctx->maxAuthAttempts;
+    ssh->appChannels = ctx->appChannels;
     ssh->highwaterCtx  = (void*)ssh;
     ssh->reqSuccessCtx = (void*)ssh;
     ssh->fs            = NULL;
@@ -12666,6 +12667,61 @@ static void SetTerminalSize(WOLFSSH* ssh, word32 widthChar, word32 heightRows,
 #endif /* WOLFSSH_TERM */
 
 
+/* Answers a shell, exec, or subsystem request. The session type, and the
+ * command for the two that carry one, are set for the callback to read and
+ * kept only if it accepts; a refused request leaves the channel as it was
+ * and the accept loop still waiting, so nothing serves a session the
+ * application turned down. Without a callback the request is accepted,
+ * unless the application drives its own channels. */
+static int DoChannelRequestSession(WOLFSSH* ssh, WOLFSSH_CHANNEL* channel,
+        byte sessionType, WS_CallbackChannelReq cb,
+        byte* buf, word32 len, word32* idx, int* rej)
+{
+    char* prevCommand = NULL;
+    byte prevType = channel->sessionType;
+    byte hasCommand = (sessionType != WOLFSSH_SESSION_SHELL);
+    int ret = WS_SUCCESS;
+
+    if (hasCommand) {
+        prevCommand = channel->command;
+        channel->command = NULL;
+        ret = GetStringAlloc(ssh->ctx->heap, &channel->command, NULL,
+                buf, len, idx);
+        if (ret == WS_SUCCESS) {
+            WLOG(WS_LOG_DEBUG, "  command = %s", channel->command);
+        }
+    }
+
+    if (ret == WS_SUCCESS) {
+        channel->sessionType = sessionType;
+        if (cb != NULL) {
+            *rej = cb(channel, ssh->channelReqCtx);
+        }
+        else {
+            *rej = ssh->appChannels;
+        }
+    }
+
+    if (ret == WS_SUCCESS && !*rej) {
+        if (prevCommand != NULL) {
+            WFREE(prevCommand, ssh->ctx->heap, DYNTYPE_STRING);
+        }
+        ssh->clientState = CLIENT_DONE;
+    }
+    else {
+        if (hasCommand) {
+            if (channel->command != NULL) {
+                WFREE(channel->command, ssh->ctx->heap, DYNTYPE_STRING);
+            }
+            channel->command = prevCommand;
+        }
+        channel->sessionType = prevType;
+    }
+
+    return ret;
+}
+
+
 static int DoChannelRequest(WOLFSSH* ssh,
                             byte* buf, word32 len, word32* idx)
 {
@@ -12721,33 +12777,17 @@ static int DoChannelRequest(WOLFSSH* ssh,
             WLOG(WS_LOG_DEBUG, "  %s = %s", name, value);
         }
         else if (ChannelRequestIs(type, typeSz, "shell")) {
-            channel->sessionType = WOLFSSH_SESSION_SHELL;
-            if (ssh->ctx->channelReqShellCb) {
-                rej = ssh->ctx->channelReqShellCb(channel, ssh->channelReqCtx);
-            }
-            ssh->clientState = CLIENT_DONE;
+            ret = DoChannelRequestSession(ssh, channel, WOLFSSH_SESSION_SHELL,
+                    ssh->ctx->channelReqShellCb, buf, len, &begin, &rej);
         }
         else if (ChannelRequestIs(type, typeSz, "exec")) {
-            ret = GetStringAlloc(ssh->ctx->heap, &channel->command, NULL,
-                    buf, len, &begin);
-            channel->sessionType = WOLFSSH_SESSION_EXEC;
-            if (ssh->ctx->channelReqExecCb) {
-                rej = ssh->ctx->channelReqExecCb(channel, ssh->channelReqCtx);
-            }
-            ssh->clientState = CLIENT_DONE;
-
-            WLOG(WS_LOG_DEBUG, "  command = %s", channel->command);
+            ret = DoChannelRequestSession(ssh, channel, WOLFSSH_SESSION_EXEC,
+                    ssh->ctx->channelReqExecCb, buf, len, &begin, &rej);
         }
         else if (ChannelRequestIs(type, typeSz, "subsystem")) {
-            ret = GetStringAlloc(ssh->ctx->heap, &channel->command, NULL,
-                    buf, len, &begin);
-            channel->sessionType = WOLFSSH_SESSION_SUBSYSTEM;
-            if (ssh->ctx->channelReqSubsysCb) {
-                rej = ssh->ctx->channelReqSubsysCb(channel, ssh->channelReqCtx);
-            }
-            ssh->clientState = CLIENT_DONE;
-
-            WLOG(WS_LOG_DEBUG, "  subsystem = %s", channel->command);
+            ret = DoChannelRequestSession(ssh, channel,
+                    WOLFSSH_SESSION_SUBSYSTEM, ssh->ctx->channelReqSubsysCb,
+                    buf, len, &begin, &rej);
         }
         #ifdef WOLFSSH_TERM
         else if (ChannelRequestIs(type, typeSz, "pty-req")) {
@@ -12886,7 +12926,7 @@ static int DoChannelRequest(WOLFSSH* ssh,
         int replyRet;
 
         if (rej) {
-            WLOG(WS_LOG_DEBUG, "Callback rejecting channel request.");
+            WLOG(WS_LOG_DEBUG, "Rejecting channel request.");
         }
         replyRet = SendChannelSuccess(ssh, channelId,
                 (ret == WS_SUCCESS && !rej));

src/ssh.c

@@ -567,10 +567,6 @@ static int DoReceiveHandshake(WOLFSSH* ssh)
 #endif /* !NO_WOLFSSH_SERVER || !NO_WOLFSSH_CLIENT */
 
 
-/* Defined below, ahead of both drivers; either can be the only one built. */
-static int SendAfterDisconnect(WOLFSSH* ssh);
-
-
 #ifndef NO_WOLFSSH_SERVER
 
 const char acceptError[] = "accept error: %s, %d";
@@ -579,6 +575,8 @@ const char acceptState[] = "accept state: %s";
 
 int wolfSSH_accept(WOLFSSH* ssh)
 {
+    byte stopState;
+
     WLOG(WS_LOG_DEBUG, "Entering wolfSSH_accept()");
 
     if (ssh == NULL)
@@ -598,6 +596,15 @@ int wolfSSH_accept(WOLFSSH* ssh)
         return WS_INVALID_STATE_E;
     }
 
+    /* In application-driven mode the state machine stops as soon as the
+     * user is authenticated; everything past that is the application's.
+     * Only stop there if the session has not already gone by: the loop
+     * below tests the stop state exactly, so a state it has stepped over
+     * would never terminate it. */
+    stopState = (ssh->appChannels
+            && ssh->acceptState <= ACCEPT_SERVER_USERAUTH_SENT) ?
+        ACCEPT_SERVER_USERAUTH_SENT : ACCEPT_CLIENT_SESSION_ESTABLISHED;
+
     /* check if data pending to be sent */
     if (ssh->outputBuffer.length > 0 &&
             ssh->acceptState < ACCEPT_CLIENT_SESSION_ESTABLISHED) {
@@ -609,7 +616,11 @@ int wolfSSH_accept(WOLFSSH* ssh)
                 ssh->acceptState != ACCEPT_SERVER_USERAUTH_ACCEPT_SENT &&
                 ssh->acceptState != ACCEPT_SERVER_KEXINIT_SENT &&
                 ssh->acceptState != ACCEPT_KEYED &&
-                ssh->acceptState != ACCEPT_SERVER_CHANNEL_ACCEPT_SENT) {
+                ssh->acceptState != ACCEPT_SERVER_CHANNEL_ACCEPT_SENT &&
+                /* Never step over where this call is meant to stop. The
+                 * loop below tests for that state exactly, and the SCP and
+                 * SFTP re-entry states sort after it. */
+                ssh->acceptState != stopState) {
                 WLOG(WS_LOG_DEBUG, "Advancing accept state");
                 ssh->acceptState++;
             }
@@ -631,7 +642,7 @@ int wolfSSH_accept(WOLFSSH* ssh)
         }
     }
 
-    while (ssh->acceptState != ACCEPT_CLIENT_SESSION_ESTABLISHED) {
+    while (ssh->acceptState != stopState) {
         switch (ssh->acceptState) {
 
             case ACCEPT_BEGIN:
@@ -721,6 +732,12 @@ int wolfSSH_accept(WOLFSSH* ssh)
                 }
                 ssh->acceptState = ACCEPT_SERVER_USERAUTH_SENT;
                 WLOG(WS_LOG_DEBUG, acceptState, "SERVER_USERAUTH_SENT");
+                if (stopState == ACCEPT_SERVER_USERAUTH_SENT) {
+                    /* The application takes it from here. Tested through
+                     * stopState so a callback that changed the flag during
+                     * this call cannot half-apply it. */
+                    break;
+                }
                 FALL_THROUGH;
 
             case ACCEPT_SERVER_USERAUTH_SENT:
@@ -764,52 +781,17 @@ int wolfSSH_accept(WOLFSSH* ssh)
 #endif /* WOLFSSH_SFTP and !NO_WOLFSSH_SERVER */
 #ifdef WOLFSSH_AGENT
                 if (ssh->useAgent) {
-                    WOLFSSH_AGENT_CTX* newAgent;
-                    WOLFSSH_CHANNEL* newChannel;
-
-                    WLOG(WS_LOG_AGENT, "Starting agent channel");
-
-                    newAgent = wolfSSH_AGENT_new(ssh->ctx->heap);
-                    if (newAgent == NULL) {
-                        ssh->error = WS_MEMORY_E;
-                        WLOG(WS_LOG_DEBUG, acceptError,
-                            "SERVER_USERAUTH_ACCEPT_DONE", ssh->error);
-                        return WS_ERROR;
-                    }
-
-                    newChannel = ChannelNew(ssh, ID_CHANTYPE_AUTH_AGENT,
-                            ssh->ctx->windowSz, ssh->ctx->maxPacketSz);
-                    if (newChannel == NULL) {
-                        wolfSSH_AGENT_free(newAgent);
-                        ssh->error = WS_MEMORY_E;
-                        WLOG(WS_LOG_DEBUG, acceptError,
-                            "SERVER_USERAUTH_ACCEPT_DONE", ssh->error);
-                        return WS_FATAL_ERROR;
-                    }
+                    int agentRet = wolfSSH_AGENT_ChannelOpen(ssh);
 
-                    ssh->error = SendChannelOpenSession(ssh, newChannel);
-                    if (ssh->error < WS_SUCCESS) {
-                        if (ssh->error == WS_WANT_WRITE ||
-                                ssh->error == WS_WANT_READ) {
-                            ChannelAppend(ssh, newChannel);
-                        }
-                        else {
-                            ChannelDelete(newChannel, ssh->ctx->heap);
-                            wolfSSH_AGENT_free(newAgent);
-                        }
+                    if (agentRet < WS_SUCCESS) {
+                        /* WS_FATAL_ERROR is the disconnect, which already
+                         * recorded WS_DISCONNECT; keep that. */
+                        if (agentRet != WS_FATAL_ERROR)
+                            ssh->error = agentRet;
                         WLOG(WS_LOG_DEBUG, acceptError,
                             "SERVER_USERAUTH_ACCEPT_DONE", ssh->error);
                         return WS_FATAL_ERROR;
                     }
-                    ChannelAppend(ssh, newChannel);
-                    newAgent->channel = newChannel->channel;
-                    if (ssh->ctx->agentCb) {
-                        ssh->ctx->agentCb(WOLFSSH_AGENT_LOCAL_SETUP,
-                                ssh->agentCbCtx);
-                    }
-                    if (ssh->agent != NULL)
-                        wolfSSH_AGENT_free(ssh->agent);
-                    ssh->agent = newAgent;
                 }
 #endif /* WOLFSSH_AGENT */
                 ssh->acceptState = ACCEPT_CLIENT_SESSION_ESTABLISHED;
@@ -1134,11 +1116,8 @@ int wolfSSH_connect(WOLFSSH* ssh)
 #endif /* NO_WOLFSSH_CLIENT */
 
 
-/* A disconnect, sent or received, ends the session, so nothing further may
- * go out. RFC 4253 section 11.1. Reads are deliberately not gated on this:
- * channel data that arrived before the disconnect is still the caller's.
- * Call only after ssh has been checked for NULL. */
-static int SendAfterDisconnect(WOLFSSH* ssh)
+/* See wolfssh/internal.h for the contract. */
+int SendAfterDisconnect(WOLFSSH* ssh)
 {
     if (ssh->disconnected) {
         WLOG(WS_LOG_DEBUG, "Send attempted after a disconnect");
@@ -3963,7 +3942,8 @@ WOLFSSH_CHANNEL* wolfSSH_ChannelFwdNewRemote(WOLFSSH* ssh,
     if (newChannel != NULL)
         ChannelAppend(ssh, newChannel);
 
-    WLOG(WS_LOG_DEBUG, "Leaving wolfSSH_ChannelFwdNewRemote(), newChannel = %p, ret = %d",
+    WLOG(WS_LOG_DEBUG,
+            "Leaving wolfSSH_ChannelFwdNewRemote(), newChannel = %p, ret = %d",
             newChannel, ret);
     return newChannel;
 }
@@ -4957,6 +4937,32 @@ int wolfSSH_CTX_SetChannelReqSubsysCb(WOLFSSH_CTX* ctx,
 }
 
 
+int wolfSSH_CTX_SetAppChannels(WOLFSSH_CTX* ctx, byte enable)
+{
+    int ret = WS_SSH_CTX_NULL_E;
+
+    if (ctx != NULL) {
+        ctx->appChannels = (enable != 0);
+        ret = WS_SUCCESS;
+    }
+
+    return ret;
+}
+
+
+int wolfSSH_SetAppChannels(WOLFSSH* ssh, byte enable)
+{
+    int ret = WS_SSH_NULL_E;
+
+    if (ssh != NULL) {
+        ssh->appChannels = (enable != 0);
+        ret = WS_SUCCESS;
+    }
+
+    return ret;
+}
+
+
 int wolfSSH_SetChannelOpenCtx(WOLFSSH* ssh, void* ctx)
 {
     int ret = WS_SSH_NULL_E;