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Cap the maximum SFTP write value to 32768 bytes

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Resolves: RHEL-5485

Signed-off-by: Sahana Prasad <sahana@redhat.com>
This commit is contained in:
Sahana Prasad 2023-09-19 12:41:20 +02:00
parent 57094428a4
commit 0e94b4d5ee
2 changed files with 40 additions and 1 deletions
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7
libssh.spec
View File

@ -1,6 +1,6 @@
Name: libssh
Version: 0.9.6
Release: 12%{?dist}
Release: 13%{?dist}
Summary: A library implementing the SSH protocol
License: LGPLv2+
URL: http://www.libssh.org
@ -17,6 +17,7 @@ Patch2: null_dereference_rekey.patch
Patch3: auth_bypass.patch
Patch4: fix_tests.patch
Patch5: covscan23.patch
Patch6: sftp_write_cap.patch
BuildRequires: cmake
BuildRequires: doxygen
@ -145,6 +146,10 @@ popd
%attr(0644,root,root) %config(noreplace) %{_sysconfdir}/libssh/libssh_server.config
%changelog
* Wed Sep 20 2023 Sahana Prasad <sahana@redhat.com> - 0.9.6-13
- Cap the maximum SFTP write value to 32768 bytes
- Resolves: RHEL-5485
* Mon May 15 2023 Norbert Pocs <npocs@redhat.com> - 0.9.6-12
- Fix loglevel regression
- Related: rhbz#2182251, rhbz#2189742

34
sftp_write_cap.patch Normal file
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@ -0,0 +1,34 @@
diff -up libssh-0.10.4/include/libssh/sftp.h-cap libssh-0.10.4/include/libssh/sftp.h
--- libssh-0.10.4/include/libssh/sftp.h-cap 2023-09-19 11:28:41.304353437 +0200
+++ libssh-0.10.4/include/libssh/sftp.h 2023-09-19 11:34:20.828666252 +0200
@@ -550,6 +550,10 @@ LIBSSH_API int sftp_async_read(sftp_file
/**
* @brief Write to a file using an opened sftp file handle.
*
+ * The maximum size of the SFTP packet payload is 32768 bytes so the count
+ * parameter is capped at this value. This is low-level function so it does not
+ * try to send more than this amount of data.
+ *
* @param file Open sftp file handle to write to.
*
* @param buf Pointer to buffer to write data.
diff -up libssh-0.10.4/src/sftp.c-cap libssh-0.10.4/src/sftp.c
--- libssh-0.10.4/src/sftp.c-cap 2023-09-19 11:29:02.897569013 +0200
+++ libssh-0.10.4/src/sftp.c 2023-09-19 11:30:36.827506743 +0200
@@ -2179,6 +2179,16 @@ ssize_t sftp_write(sftp_file file, const
id = sftp_get_new_id(file->sftp);
+ /* limit the writes to the maximum specified in Section 3 of
+ * https://datatracker.ietf.org/doc/html/draft-ietf-secsh-filexfer-02
+ *
+ * FIXME: This value should be adjusted to the value from the
+ * limits@openssh.com extension if supported
+ * TODO: We should iterate over the blocks rather than writing less than
+ * requested to provide less surprises to the calling applications.
+ */
+ count = count > 32768 ? 32768 : count;
+
rc = ssh_buffer_pack(buffer,
"dSqdP",
id,