Re: [PATCH 2/2] cifs: dynamic allocation of ntlmssp blob

From: Steve French
Date: Thu May 26 2016 - 14:30:44 EST

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In reply to: Jerome Marchand: "[PATCH 2/2] cifs: dynamic allocation of ntlmssp blob"
Next in thread: Steve French: "Re: [PATCH 2/2] cifs: dynamic allocation of ntlmssp blob"
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Your patch makes code a little clearer, so I don't mind merging it,
but the two values are the same so this patch should have no effect.

On Thu, May 26, 2016 at 4:52 AM, Jerome Marchand <jmarchan@xxxxxxxxxx> wrote:
> In sess_auth_rawntlmssp_authenticate(), the ntlmssp blob is allocated
> statically and its size is an "empirical" 5*sizeof(struct
> _AUTHENTICATE_MESSAGE) (320B on x86_64). I don't know where this value
> comes from or if it was ever appropriate, but it is currently
> insufficient: the user and domain name in UTF16 could take 1kB by
> themselves. Because of that, build_ntlmssp_auth_blob() might corrupt
> memory (out-of-bounds write). The size of ntlmssp_blob in
> SMB2_sess_setup() is too small too (sizeof(struct _NEGOTIATE_MESSAGE)
> + 500).
>
> This patch allocates the blob dynamically in
> build_ntlmssp_auth_blob().
>
> Signed-off-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
> ---
> fs/cifs/ntlmssp.h | 2 +-
> fs/cifs/sess.c | 76 ++++++++++++++++++++++++++++++-------------------------
> fs/cifs/smb2pdu.c | 10 ++------
> 3 files changed, 45 insertions(+), 43 deletions(-)
>
> diff --git a/fs/cifs/ntlmssp.h b/fs/cifs/ntlmssp.h
> index 848249f..3079b38 100644
> --- a/fs/cifs/ntlmssp.h
> +++ b/fs/cifs/ntlmssp.h
> @@ -133,6 +133,6 @@ typedef struct _AUTHENTICATE_MESSAGE {
>
> int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len, struct cifs_ses *ses);
> void build_ntlmssp_negotiate_blob(unsigned char *pbuffer, struct cifs_ses *ses);
> -int build_ntlmssp_auth_blob(unsigned char *pbuffer, u16 *buflen,
> +int build_ntlmssp_auth_blob(unsigned char **pbuffer, u16 *buflen,
> struct cifs_ses *ses,
> const struct nls_table *nls_cp);
> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> index c3d086e..463bed7 100644
> --- a/fs/cifs/sess.c
> +++ b/fs/cifs/sess.c
> @@ -364,19 +364,43 @@ void build_ntlmssp_negotiate_blob(unsigned char *pbuffer,
> sec_blob->DomainName.MaximumLength = 0;
> }
>
> -/* We do not malloc the blob, it is passed in pbuffer, because its
> - maximum possible size is fixed and small, making this approach cleaner.
> - This function returns the length of the data in the blob */
> -int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> +int size_of_ntlmssp_blob(struct cifs_ses *ses)
> +{
> + int sz = sizeof(AUTHENTICATE_MESSAGE) + ses->auth_key.len
> + - CIFS_SESS_KEY_SIZE + CIFS_CPHTXT_SIZE + 2;
> +
> + if (ses->domainName)
> + sz += 2 * strnlen(ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
> + else
> + sz += 2;
> +
> + if (ses->user_name)
> + sz += 2 * strnlen(ses->user_name, CIFS_MAX_USERNAME_LEN);
> + else
> + sz += 2;
> +
> + return sz;
> +}
> +
> +int build_ntlmssp_auth_blob(unsigned char **pbuffer,
> u16 *buflen,
> struct cifs_ses *ses,
> const struct nls_table *nls_cp)
> {
> int rc;
> - AUTHENTICATE_MESSAGE *sec_blob = (AUTHENTICATE_MESSAGE *)pbuffer;
> + AUTHENTICATE_MESSAGE *sec_blob;
> __u32 flags;
> unsigned char *tmp;
>
> + rc = setup_ntlmv2_rsp(ses, nls_cp);
> + if (rc) {
> + cifs_dbg(VFS, "Error %d during NTLMSSP authentication\n", rc);
> + *buflen = 0;
> + goto setup_ntlmv2_ret;
> + }
> + *pbuffer = kmalloc(size_of_ntlmssp_blob(ses), GFP_KERNEL);
> + sec_blob = (AUTHENTICATE_MESSAGE *)*pbuffer;
> +
> memcpy(sec_blob->Signature, NTLMSSP_SIGNATURE, 8);
> sec_blob->MessageType = NtLmAuthenticate;
>
> @@ -391,7 +415,7 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
> }
>
> - tmp = pbuffer + sizeof(AUTHENTICATE_MESSAGE);
> + tmp = *pbuffer + sizeof(AUTHENTICATE_MESSAGE);
> sec_blob->NegotiateFlags = cpu_to_le32(flags);
>
> sec_blob->LmChallengeResponse.BufferOffset =
> @@ -399,13 +423,9 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> sec_blob->LmChallengeResponse.Length = 0;
> sec_blob->LmChallengeResponse.MaximumLength = 0;
>
> - sec_blob->NtChallengeResponse.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->NtChallengeResponse.BufferOffset =
> + cpu_to_le32(tmp - *pbuffer);
> if (ses->user_name != NULL) {
> - rc = setup_ntlmv2_rsp(ses, nls_cp);
> - if (rc) {
> - cifs_dbg(VFS, "Error %d during NTLMSSP authentication\n", rc);
> - goto setup_ntlmv2_ret;
> - }
> memcpy(tmp, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
> ses->auth_key.len - CIFS_SESS_KEY_SIZE);
> tmp += ses->auth_key.len - CIFS_SESS_KEY_SIZE;
> @@ -423,7 +443,7 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> }
>
> if (ses->domainName == NULL) {
> - sec_blob->DomainName.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->DomainName.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->DomainName.Length = 0;
> sec_blob->DomainName.MaximumLength = 0;
> tmp += 2;
> @@ -432,14 +452,14 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> len = cifs_strtoUTF16((__le16 *)tmp, ses->domainName,
> CIFS_MAX_DOMAINNAME_LEN, nls_cp);
> len *= 2; /* unicode is 2 bytes each */
> - sec_blob->DomainName.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->DomainName.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->DomainName.Length = cpu_to_le16(len);
> sec_blob->DomainName.MaximumLength = cpu_to_le16(len);
> tmp += len;
> }
>
> if (ses->user_name == NULL) {
> - sec_blob->UserName.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->UserName.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->UserName.Length = 0;
> sec_blob->UserName.MaximumLength = 0;
> tmp += 2;
> @@ -448,13 +468,13 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> len = cifs_strtoUTF16((__le16 *)tmp, ses->user_name,
> CIFS_MAX_USERNAME_LEN, nls_cp);
> len *= 2; /* unicode is 2 bytes each */
> - sec_blob->UserName.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->UserName.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->UserName.Length = cpu_to_le16(len);
> sec_blob->UserName.MaximumLength = cpu_to_le16(len);
> tmp += len;
> }
>
> - sec_blob->WorkstationName.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->WorkstationName.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->WorkstationName.Length = 0;
> sec_blob->WorkstationName.MaximumLength = 0;
> tmp += 2;
> @@ -463,19 +483,19 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
> (ses->ntlmssp->server_flags & NTLMSSP_NEGOTIATE_EXTENDED_SEC))
> && !calc_seckey(ses)) {
> memcpy(tmp, ses->ntlmssp->ciphertext, CIFS_CPHTXT_SIZE);
> - sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->SessionKey.Length = cpu_to_le16(CIFS_CPHTXT_SIZE);
> sec_blob->SessionKey.MaximumLength =
> cpu_to_le16(CIFS_CPHTXT_SIZE);
> tmp += CIFS_CPHTXT_SIZE;
> } else {
> - sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
> + sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - *pbuffer);
> sec_blob->SessionKey.Length = 0;
> sec_blob->SessionKey.MaximumLength = 0;
> }
>
> + *buflen = tmp - *pbuffer;
> setup_ntlmv2_ret:
> - *buflen = tmp - pbuffer;
> return rc;
> }
>
> @@ -1266,7 +1286,7 @@ sess_auth_rawntlmssp_authenticate(struct sess_data *sess_data)
> struct cifs_ses *ses = sess_data->ses;
> __u16 bytes_remaining;
> char *bcc_ptr;
> - char *ntlmsspblob = NULL;
> + unsigned char *ntlmsspblob = NULL;
> u16 blob_len;
>
> cifs_dbg(FYI, "rawntlmssp session setup authenticate phase\n");
> @@ -1279,19 +1299,7 @@ sess_auth_rawntlmssp_authenticate(struct sess_data *sess_data)
> /* Build security blob before we assemble the request */
> pSMB = (SESSION_SETUP_ANDX *)sess_data->iov[0].iov_base;
> smb_buf = (struct smb_hdr *)pSMB;
> - /*
> - * 5 is an empirical value, large enough to hold
> - * authenticate message plus max 10 of av paris,
> - * domain, user, workstation names, flags, etc.
> - */
> - ntlmsspblob = kzalloc(5*sizeof(struct _AUTHENTICATE_MESSAGE),
> - GFP_KERNEL);
> - if (!ntlmsspblob) {
> - rc = -ENOMEM;
> - goto out;
> - }
> -
> - rc = build_ntlmssp_auth_blob(ntlmsspblob,
> + rc = build_ntlmssp_auth_blob(&ntlmsspblob,
> &blob_len, ses, sess_data->nls_cp);
> if (rc)
> goto out_free_ntlmsspblob;
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 8f38e33..c3e61a7 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -588,7 +588,7 @@ SMB2_sess_setup(const unsigned int xid, struct cifs_ses *ses,
> u16 blob_length = 0;
> struct key *spnego_key = NULL;
> char *security_blob = NULL;
> - char *ntlmssp_blob = NULL;
> + unsigned char *ntlmssp_blob = NULL;
> bool use_spnego = false; /* else use raw ntlmssp */
>
> cifs_dbg(FYI, "Session Setup\n");
> @@ -713,13 +713,7 @@ ssetup_ntlmssp_authenticate:
> iov[1].iov_len = blob_length;
> } else if (phase == NtLmAuthenticate) {
> req->hdr.SessionId = ses->Suid;
> - ntlmssp_blob = kzalloc(sizeof(struct _NEGOTIATE_MESSAGE) + 500,
> - GFP_KERNEL);
> - if (ntlmssp_blob == NULL) {
> - rc = -ENOMEM;
> - goto ssetup_exit;
> - }
> - rc = build_ntlmssp_auth_blob(ntlmssp_blob, &blob_length, ses,
> + rc = build_ntlmssp_auth_blob(&ntlmssp_blob, &blob_length, ses,
> nls_cp);
> if (rc) {
> cifs_dbg(FYI, "build_ntlmssp_auth_blob failed %d\n",
> --
> 2.5.5
>
> --
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--
Thanks,

Steve

Next message: Linus Torvalds: "Re: [GIT PULL] Ceph updates for 4.7-rc1"
Previous message: Waiman Long: "[PATCH 1/2] locking/pvqspinlock: Fix missed PV wakeup problem"
In reply to: Jerome Marchand: "[PATCH 2/2] cifs: dynamic allocation of ntlmssp blob"
Next in thread: Steve French: "Re: [PATCH 2/2] cifs: dynamic allocation of ntlmssp blob"
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