wolfsftp: keep the local file when resuming a get

- The Windows local open in wolfSSH_SFTP_Get() passes OPEN_EXISTING
  when the write offset is nonzero and CREATE_ALWAYS otherwise, and
  drops FILE_APPEND_DATA from the desired access. A new
  DWORD creationDisp replaces the block-scoped desiredAccess.
- That open reports INVALID_HANDLE_VALUE as WS_BAD_FILE_E and moves to
  STATE_GET_CLEANUP; the OVERLAPPED offset is set from gOfst on every
  open rather than only when resuming.
- STATE_GET_LOOKUP_OFFSET stats the local destination when the saved
  offset is nonzero and clears the offset unless the reported size
  matches it exactly. WS_SFTP_GET_STATE carries the attributes it
  reads.
- tests/api.c adds test_wolfSSH_SFTP_GetResume() and its
  sftpGetToCompletion() helper, five cases over the resume paths,
  built where the hosted file wrappers are available.
- .gitignore covers the wolfssh_12547_*.tmp fixtures that test leaves
  behind on an aborted run.

Issue: F-12547

Author: yosuke-wolfssl

.gitignore

@@ -85,11 +85,10 @@ keys/*-ossh-*cert.pub
 random-test.txt
 random-test-result.txt
 test.dat
-# Scratch file the api tests write in the working directory. Removed on a
-# clean run, left behind when one aborts.
+# Scratch files the api and regression tests write in the working
+# directory. Removed on a clean run, left behind when one aborts.
 ossh-cert-line.tmp
-# Same for the regression tests' known_hosts fixtures, named by pid.
-wolfssh_kh_*.tmp
+wolfssh_*.tmp
 regress_known_hosts*.tmp
 
 # test output

src/wolfsftp.c

@@ -9775,6 +9775,9 @@ int wolfSSH_SFTP_Get(WOLFSSH* ssh, char* from,
     WS_SFTP_GET_STATE* state = NULL;
     int sz;
     int ret = WS_SUCCESS;
+#ifdef USE_WINDOWS_API
+    DWORD creationDisp;
+#endif
 
     WLOG(WS_LOG_SFTP, "Entering wolfSSH_SFTP_Get()");
     if (ssh == NULL || from == NULL || to == NULL)
@@ -9853,6 +9856,23 @@ int wolfSSH_SFTP_Get(WOLFSSH* ssh, char* from,
                 /* if resuming then check for saved offset */
                 if (resume) {
                     wolfSSH_SFTP_GetOfst(ssh, from, to, state->gOfst);
+
+                    /* a saved offset is only usable if the local file still
+                     * holds exactly that many bytes */
+                    if (state->gOfst[0] > 0 || state->gOfst[1] > 0) {
+                        WMEMSET(&state->attrib, 0, sizeof(state->attrib));
+                        if (SFTP_GetAttributes(ssh->fs, to, &state->attrib, 1,
+                                    ssh->ctx->heap) != WS_SUCCESS
+                                || (state->attrib.flags
+                                    & WOLFSSH_FILEATRB_SIZE) == 0
+                                || state->attrib.sz[0] != state->gOfst[0]
+                                || state->attrib.sz[1] != state->gOfst[1]) {
+                            WLOG(WS_LOG_SFTP,
+                                    "Size does not match, starting over");
+                            state->gOfst[0] = 0;
+                            state->gOfst[1] = 0;
+                        }
+                    }
                 }
                 state->state = STATE_GET_OPEN_LOCAL;
                 FALL_THROUGH;
@@ -9865,20 +9885,23 @@ int wolfSSH_SFTP_Get(WOLFSSH* ssh, char* from,
                     else
                         ret = WFOPEN(ssh->fs, &state->fl, to, WOLFSSH_O_WRONLY);
             #elif defined(USE_WINDOWS_API)
-                    {
-                        DWORD desiredAccess = GENERIC_WRITE;
-                        if (state->gOfst[0] > 0 || state->gOfst[1] > 0)
-                            desiredAccess |= FILE_APPEND_DATA;
-                        state->fileHandle = WS_CreateFileA(to, desiredAccess,
-                            (FILE_SHARE_DELETE | FILE_SHARE_READ |
-                             FILE_SHARE_WRITE), CREATE_ALWAYS,
-                            FILE_ATTRIBUTE_NORMAL, ssh->ctx->heap);
-                    }
-                    if (resume) {
-                        WMEMSET(&state->offset, 0, sizeof(OVERLAPPED));
-                        state->offset.OffsetHigh = state->gOfst[1];
-                        state->offset.Offset = state->gOfst[0];
+                    creationDisp = CREATE_ALWAYS;
+                    if (state->gOfst[0] > 0 || state->gOfst[1] > 0)
+                        creationDisp = OPEN_EXISTING;
+                    state->fileHandle = WS_CreateFileA(to, GENERIC_WRITE,
+                        (FILE_SHARE_DELETE | FILE_SHARE_READ |
+                         FILE_SHARE_WRITE), creationDisp,
+                        FILE_ATTRIBUTE_NORMAL, ssh->ctx->heap);
+                    if (state->fileHandle == INVALID_HANDLE_VALUE) {
+                        WLOG(WS_LOG_SFTP, "Unable to open output file");
+                        ssh->error = WS_BAD_FILE_E;
+                        ret = WS_FATAL_ERROR;
+                        state->state = STATE_GET_CLEANUP;
+                        continue;
                     }
+                    WMEMSET(&state->offset, 0, sizeof(OVERLAPPED));
+                    state->offset.OffsetHigh = state->gOfst[1];
+                    state->offset.Offset = state->gOfst[0];
                 #else
                     if (state->gOfst[0] > 0 || state->gOfst[1] > 0)
                         ret = WFOPEN(ssh->fs, &state->fl, to, "ab");

tests/api.c

@@ -5901,6 +5901,24 @@ static int sftpPutToCompletion(WOLFSSH* ssh, char* from, char* to, byte resume)
 
     return ret;
 }
+
+
+/* Drives one wolfSSH_SFTP_Get() to a terminal result. */
+static int sftpGetToCompletion(WOLFSSH* ssh, char* from, char* to, byte resume)
+{
+    int ret = WS_FATAL_ERROR;
+    int tries;
+
+    for (tries = 0; tries < SFTP_MAX_RETRY_TRIES; tries++) {
+        ret = wolfSSH_SFTP_Get(ssh, from, to, resume, NULL);
+        if (ret == WS_SUCCESS ||
+                !sftp_error_is_notice(wolfSSH_get_error(ssh))) {
+            break;
+        }
+    }
+
+    return ret;
+}
 #endif /* !NO_FILESYSTEM && !WOLFSSH_USER_FILESYSTEM && !WOLFSSH_ZEPHYR */
 
 
@@ -6040,6 +6058,133 @@ static void test_wolfSSH_SFTP_PutResume(void)
 }
 
 
+/* A resumed get must keep the bytes already at the local destination, and
+ * must only resume onto one whose size matches the saved offset. The
+ * echoserver shares this process, so the "remote" file is local. */
+static void test_wolfSSH_SFTP_GetResume(void)
+{
+/* staging both files needs the hosted fopen()/getcwd() wrappers */
+#if !defined(NO_FILESYSTEM) && !defined(WOLFSSH_USER_FILESYSTEM) && \
+    !defined(WOLFSSH_ZEPHYR)
+    func_args ser;
+    tcp_ready ready;
+    int argsCount;
+    WS_SOCKET_T clientFd;
+
+    const char* args[10];
+    WOLFSSH_CTX* ctx = NULL;
+    WOLFSSH*     ssh = NULL;
+
+    THREAD_TYPE serThread;
+
+    byte src[SFTP_PUT_RESUME_SZ];
+    byte stale[SFTP_PUT_RESUME_SZ + SFTP_PUT_RESUME_OFST];
+    byte expect[SFTP_PUT_RESUME_SZ];
+    word32 ofst[2];
+    char srcName[] = "wolfssh_12547_src.tmp";
+    char dstName[] = "wolfssh_12547_dst.tmp";
+
+    WMEMSET(&ser, 0, sizeof(func_args));
+
+    argsCount = 0;
+    args[argsCount++] = ".";
+    args[argsCount++] = "-1";
+    args[argsCount++] = "-p";
+    args[argsCount++] = "0";
+    ser.argv   = (char**)args;
+    ser.argc   = argsCount;
+    ser.signal = &ready;
+    InitTcpReady(ser.signal);
+    ThreadStart(echoserver_test, (void*)&ser, &serThread);
+    WaitTcpReady(&ready);
+
+    sftp_client_connect(&ctx, &ssh, ready.port);
+    AssertNotNull(ctx);
+    AssertNotNull(ssh);
+
+    sftpPutFillPattern(src, (word32)sizeof(src));
+    WMEMSET(stale, 0xFF, sizeof(stale));
+    AssertIntEQ(sftpPutWriteFile(srcName, src, (word32)sizeof(src)), 0);
+
+    /* the saved offset matches the destination, so the download picks up
+     * where it left off. Staging a prefix unlike the source, and expecting it
+     * back untouched, is what separates a resume from a full re-download. */
+    AssertIntEQ(sftpPutWriteFile(dstName, stale, SFTP_PUT_RESUME_OFST), 0);
+    WMEMCPY(expect, stale, SFTP_PUT_RESUME_OFST);
+    WMEMCPY(expect + SFTP_PUT_RESUME_OFST, src + SFTP_PUT_RESUME_OFST,
+            sizeof(expect) - SFTP_PUT_RESUME_OFST);
+    ofst[0] = SFTP_PUT_RESUME_OFST;
+    ofst[1] = 0;
+    AssertIntEQ(wolfSSH_SFTP_SaveOfst(ssh, srcName, dstName, ofst),
+            WS_SUCCESS);
+    AssertIntEQ(sftpGetToCompletion(ssh, srcName, dstName, 1), WS_SUCCESS);
+    AssertIntEQ(sftpPutFileMatches(dstName, expect, (word32)sizeof(expect)),
+            0);
+
+    /* the destination is gone, so the whole file is fetched again */
+    WREMOVE(NULL, dstName);
+    ofst[0] = SFTP_PUT_RESUME_OFST;
+    ofst[1] = 0;
+    AssertIntEQ(wolfSSH_SFTP_SaveOfst(ssh, srcName, dstName, ofst),
+            WS_SUCCESS);
+    AssertIntEQ(sftpGetToCompletion(ssh, srcName, dstName, 1), WS_SUCCESS);
+    AssertIntEQ(sftpPutFileMatches(dstName, src, (word32)sizeof(src)), 0);
+
+    /* the destination is shorter than the saved offset, so the whole file is
+     * fetched again */
+    AssertIntEQ(sftpPutWriteFile(dstName, stale, SFTP_PUT_RESUME_OFST / 2), 0);
+    ofst[0] = SFTP_PUT_RESUME_OFST;
+    ofst[1] = 0;
+    AssertIntEQ(wolfSSH_SFTP_SaveOfst(ssh, srcName, dstName, ofst),
+            WS_SUCCESS);
+    AssertIntEQ(sftpGetToCompletion(ssh, srcName, dstName, 1), WS_SUCCESS);
+    AssertIntEQ(sftpPutFileMatches(dstName, src, (word32)sizeof(src)), 0);
+
+    /* the destination is longer than the saved offset, so the whole file is
+     * fetched again */
+    AssertIntEQ(sftpPutWriteFile(dstName, stale, SFTP_PUT_RESUME_OFST * 2), 0);
+    ofst[0] = SFTP_PUT_RESUME_OFST;
+    ofst[1] = 0;
+    AssertIntEQ(wolfSSH_SFTP_SaveOfst(ssh, srcName, dstName, ofst),
+            WS_SUCCESS);
+    AssertIntEQ(sftpGetToCompletion(ssh, srcName, dstName, 1), WS_SUCCESS);
+    AssertIntEQ(sftpPutFileMatches(dstName, src, (word32)sizeof(src)), 0);
+
+    /* a plain get still truncates a longer destination */
+    AssertIntEQ(sftpPutWriteFile(dstName, stale, (word32)sizeof(stale)), 0);
+    AssertIntEQ(sftpGetToCompletion(ssh, srcName, dstName, 0), WS_SUCCESS);
+    AssertIntEQ(sftpPutFileMatches(dstName, src, (word32)sizeof(src)), 0);
+
+    WREMOVE(NULL, dstName);
+    WREMOVE(NULL, srcName);
+
+    /* take care of re-keying state before shutdown call */
+    while (wolfSSH_get_error(ssh) == WS_REKEYING) {
+        wolfSSH_worker(ssh, NULL);
+    }
+
+    argsCount = AbsorbBenignReset(ssh, wolfSSH_shutdown(ssh));
+#if DEFAULT_HIGHWATER_MARK < 8000
+    if (argsCount == WS_REKEYING) {
+        argsCount = WS_SUCCESS;
+    }
+#endif
+    AssertIntEQ(argsCount, WS_SUCCESS);
+
+    clientFd = wolfSSH_get_fd(ssh);
+    WCLOSESOCKET(clientFd);
+
+    wolfSSH_free(ssh);
+    wolfSSH_CTX_free(ctx);
+#ifdef WOLFSSH_ZEPHYR
+    k_sleep(Z_TIMEOUT_TICKS(100));
+#endif
+    ThreadJoin(serThread);
+    FreeTcpReady(&ready);
+#endif /* !NO_FILESYSTEM && !WOLFSSH_USER_FILESYSTEM && !WOLFSSH_ZEPHYR */
+}
+
+
 #else /* WOLFSSH_SFTP && !NO_WOLFSSH_CLIENT && !SINGLE_THREADED */
 static void test_wolfSSH_SFTP_SendReadPacket(void) { ; }
 static void test_wolfSSH_SFTP_PartialSend(void) { ; }
@@ -6051,6 +6196,7 @@ static void test_wolfSSH_SFTP_SetConfinePath(void) { ; }
 static void test_wolfSSH_SFTP_SetDefaultPath(void) { ; }
 static void test_wolfSSH_SFTP_SaveOfst(void) { ; }
 static void test_wolfSSH_SFTP_PutResume(void) { ; }
+static void test_wolfSSH_SFTP_GetResume(void) { ; }
 #endif /* WOLFSSH_SFTP && !NO_WOLFSSH_CLIENT && !SINGLE_THREADED */
 
 
@@ -7999,6 +8145,7 @@ int wolfSSH_ApiTest(int argc, char** argv)
     test_wolfSSH_SFTP_SetDefaultPath();
     test_wolfSSH_SFTP_SaveOfst();
     test_wolfSSH_SFTP_PutResume();
+    test_wolfSSH_SFTP_GetResume();
 
     /* Either SCP or SFTP */
     test_wolfSSH_RealPath();