On Tue, Sep 14, 2010 at 6:23 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Mon, 13 Sep 2010 14:15:22 -0500
> shirishpargaonkar@xxxxxxxxx wrote:
>
>> From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
>>
>>
>> Attribue Value (AV) pairs or Target Info (TI) pairs are part of
>> ntlmv2 authentication.
>> Structure ntlmv2_resp had only definition for two av pairs.
>> So removed it, and now allocation of av pairs is dynamic.
>> For servers like Windows 7/2008, av pairs sent by server in
>> challege packet (type 2 in the ntlmssp exchange/negotiation) can
>> vary.
>>
>> Server sends them during ntlmssp negotiation. So when ntlmssp is used
>> as an authentication mechanism, type 2 challenge packet from server
>> has this information. Pluck it and use the entire blob for
>> authenticaiton purpose. If user has not specified, extract
>> (netbios) domain name from the av pairs which is used to calculate
>> ntlmv2 hash. Servers like Windows 7 are particular about the AV pair
>> blob.
>>
>> Servers like Windows 2003, are not very strict about the contents
>> of av pair blob used during ntlmv2 authentication.
>> So when security mechanism such as ntlmv2 is used (not ntlmv2 in ntlmssp),
>> there is no negotiation and so genereate a minimal blob that gets
>> used in ntlmv2 authentication as well as gets sent.
>>
>> Fields tilen and tilbob are session specific. AV pair values are defined.
>>
>> To calculate ntlmv2 response we need ti/av pair blob.
>>
>> For sec mech like ntlmssp, the blob is plucked from type 2 response from
>> the server. From this blob, netbios name of the domain is retrieved,
>> if user has not already provided, to be included in the Target String
>> as part of ntlmv2 hash calculations.
>>
>> For sec mech like ntlmv2, create a minimal, two av pair blob.
>>
>> The allocated blob is freed in case of error. In case there is no error,
>> this blob is used in calculating ntlmv2 response (in CalcNTLMv2_response)
>> and is also copied on the response to the server, and then freed.
>>
>> The type 3 ntlmssp response is prepared on a buffer,
>> 5 * sizeof of struct _AUTHENTICATE_MESSAGE, an empirical value large
>> enough to hold _AUTHENTICATE_MESSAGE plus a blob with max possible
>> 10 values as part of ntlmv2 response and lmv2 keys and domain, user,
>> workstation names etc.
>>
>> Also, kerberos gets selected as a default mechanism if server supports it,
>> over the other security mechanisms.
>>
>>
>> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
>> ---
>> fs/cifs/cifsencrypt.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++---
>> fs/cifs/cifsglob.h | 2 +
>> fs/cifs/cifspdu.h | 1 -
>> fs/cifs/cifsproto.h | 2 +-
>> fs/cifs/cifssmb.c | 16 ++++---
>> fs/cifs/connect.c | 2 +
>> fs/cifs/ntlmssp.h | 15 ++++++
>> 7 files changed, 144 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
>> index eed70ca..960c948 100644
>> --- a/fs/cifs/cifsencrypt.c
>> +++ b/fs/cifs/cifsencrypt.c
>> @@ -27,6 +27,7 @@
>> #include "md5.h"
>> #include "cifs_unicode.h"
>> #include "cifsproto.h"
>> +#include "ntlmssp.h"
>> #include <linux/ctype.h>
>> #include <linux/random.h>
>>
>> @@ -262,6 +263,87 @@ void calc_lanman_hash(const char *password, const char *cryptkey, bool encrypt,
>> }
>> #endif /* CIFS_WEAK_PW_HASH */
>>
>> +/* This is just a filler for ntlmv2 type of security mechanisms.
>> + * Older servers are not very particular about the contents of av pairs
>> + * in the blob and for sec mechs like ntlmv2, there is no negotiation
>> + * as in ntlmssp, so unless domain and server netbios and dns names
>> + * are specified, there is no way to obtain name. In case of ntlmssp,
>> + * server provides that info in type 2 challenge packet
>> + */
>> +static int
>> +build_avpair_blob(struct cifsSesInfo *ses)
>> +{
>> + struct ntlmssp2_name *attrptr;
>> +
>> + ses->tilen = 2 * sizeof(struct ntlmssp2_name);
>> + ses->tiblob = kzalloc(ses->tilen, GFP_KERNEL);
>> + if (!ses->tiblob) {
>> + ses->tilen = 0;
>> + cERROR(1, "Challenge target info allocation failure");
>> + return -ENOMEM;
>> + }
>> + attrptr = (struct ntlmssp2_name *) ses->tiblob;
>> + attrptr->type = cpu_to_le16(NTLMSSP_DOMAIN_TYPE);
>> +
>> + return 0;
>> +}
>> +
>> +/* Server has provided av pairs/target info in the type 2 challenge
>> + * packet and we have plucked it and stored within smb session.
>> + * We parse that blob here to find netbios domain name to be used
>> + * as part of ntlmv2 authentication (in Target String), if not already
>> + * specified on the command line.
>> + * If this function returns without any error but without fetching
>> + * domain name, authentication may fail against some server but
>> + * may not fail against other (those who are not very particular
>> + * about target string i.e. for some, just user name might suffice.
>> + */
>> +static int
>> +find_domain_name(struct cifsSesInfo *ses)
>> +{
>> + unsigned int attrsize;
>> + unsigned int type;
>> + unsigned char *blobptr;
>> + unsigned char *blobend;
>> + struct ntlmssp2_name *attrptr;
>> +
>> + if (!ses->tilen || !ses->tiblob)
>> + return 0;
>> +
>> + if (ses->tilen < sizeof(struct ntlmssp2_name))
>> + return 0;
>> +
>> + blobend = ses->tiblob + ses->tilen;
>> + blobptr = ses->tiblob;
>> + attrptr = (struct ntlmssp2_name *) blobptr;
>> +
>> + while (blobptr <= blobend) {
>> + type = le16_to_cpu(attrptr->type);
>> + if (type == NTLMSSP_AV_EOL)
>> + break;
>> + blobptr += 2; /* advance attr type */
>> + attrsize = le16_to_cpu(attrptr->length);
>> + blobptr += 2; /* advance attr size */
>
> Again, there's no check to see whether any of these
> lengths fall within the blob. It would be trivial for an
> attacker with access to a compromised server to craft a
> NTLMSSP response that has a NTLMSSP_AV_NB_DOMAIN_NAME
> field with a huge length, far beyond the end of the
> blob. This code will then likely oops in cifs_from_ucs2.
OK, will address this.
>
>> + if (type == NTLMSSP_AV_NB_DOMAIN_NAME) {
>> + if (!ses->domainName) {
>> + ses->domainName =
>> + kmalloc(attrsize + 1, GFP_KERNEL);
>> + if (!ses->domainName)
>> + return -ENOMEM;
>> + cifs_from_ucs2(ses->domainName,
>> + (__le16 *)blobptr,
>> + attrptr->length,
>> + attrptr->length,
>> + load_nls_default(), false);
> ^^^^^^
> You can probably break here, right?
>> + }
>> + }
>> + blobptr += attrsize; /* advance attr value */
>> + attrptr = (struct ntlmssp2_name *) blobptr;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> static int calc_ntlmv2_hash(struct cifsSesInfo *ses,
>> const struct nls_table *nls_cp)
>> {
>> @@ -321,7 +403,8 @@ calc_exit_2:
>> return rc;
>> }
>>
>> -void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
>> +int
>> +setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
>> const struct nls_table *nls_cp)
>> {
>> int rc;
>> @@ -333,15 +416,29 @@ void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
>> buf->time = cpu_to_le64(cifs_UnixTimeToNT(CURRENT_TIME));
>> get_random_bytes(&buf->client_chal, sizeof(buf->client_chal));
>> buf->reserved2 = 0;
>> - buf->names[0].type = cpu_to_le16(NTLMSSP_DOMAIN_TYPE);
>> - buf->names[0].length = 0;
>> - buf->names[1].type = 0;
>> - buf->names[1].length = 0;
>> +
>> + if (ses->server->secType == RawNTLMSSP) {
>> + if (!ses->domainName) {
>> + rc = find_domain_name(ses);
>> + if (rc) {
>> + cERROR(1, "error %d finding domain name", rc);
>> + goto setup_ntlmv2_rsp_ret;
>> + }
>> + }
>> + } else {
>> + rc = build_avpair_blob(ses);
>> + if (rc) {
>> + cERROR(1, "error %d building av pair blob", rc);
>> + return rc;
>> + }
>> + }
>>
>> /* calculate buf->ntlmv2_hash */
>> rc = calc_ntlmv2_hash(ses, nls_cp);
>> - if (rc)
>> + if (rc) {
>> cERROR(1, "could not get v2 hash rc %d", rc);
>> + goto setup_ntlmv2_rsp_ret;
>> + }
>> CalcNTLMv2_response(ses, resp_buf);
>>
>> /* now calculate the MAC key for NTLMv2 */
>> @@ -352,6 +449,14 @@ void setup_ntlmv2_rsp(struct cifsSesInfo *ses, char *resp_buf,
>> memcpy(&ses->server->session_key.data.ntlmv2.resp, resp_buf,
>> sizeof(struct ntlmv2_resp));
>> ses->server->session_key.len = 16 + sizeof(struct ntlmv2_resp);
>> +
>> + return 0;
>> +
>> +setup_ntlmv2_rsp_ret:
>> + kfree(ses->tiblob);
>> + ses->tilen = 0;
>> +
>> + return rc;
>
> So, this blob only gets freed when there's an problem calculating the
> hash? What's the value in keeping this around after session setup is
> done?
>
This blob will get freed in build_ntlmssp_negotiate_blob() once the blob
is copied while building type 3 packet of ntlmssp negotiation.
That is in patch 3/4.
>> }
>>
>> void CalcNTLMv2_response(const struct cifsSesInfo *ses,
>> @@ -365,6 +470,10 @@ void CalcNTLMv2_response(const struct cifsSesInfo *ses,
>> hmac_md5_update(v2_session_response+8,
>> sizeof(struct ntlmv2_resp) - 8, &context);
>>
>> + if (ses->tilen)
>> + hmac_md5_update(ses->tiblob,
>> + ses->tilen, &context);
>> +
> ^^^^^^^
> nit: that looks like it would fit on one line
Yes, will fix that.
>
>> hmac_md5_final(v2_session_response, &context);
>> /* cifs_dump_mem("v2_sess_rsp: ", v2_session_response, 32); */
>> }
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index 14dfa9a..c68f31c 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -222,6 +222,8 @@ struct cifsSesInfo {
>> char userName[MAX_USERNAME_SIZE + 1];
>> char *domainName;
>> char *password;
>> + unsigned int tilen; /* length of the target info blob */
>> + unsigned char *tiblob; /* target info blob in challenge response */
>> bool need_reconnect:1; /* connection reset, uid now invalid */
>> };
>> /* no more than one of the following three session flags may be set */
>> diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
>> index 14d036d..b0f4b56 100644
>> --- a/fs/cifs/cifspdu.h
>> +++ b/fs/cifs/cifspdu.h
>> @@ -663,7 +663,6 @@ struct ntlmv2_resp {
>> __le64 time;
>> __u64 client_chal; /* random */
>> __u32 reserved2;
>> - struct ntlmssp2_name names[2];
>> /* array of name entries could follow ending in minimum 4 byte struct */
>> } __attribute__((packed));
>>
>> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
>> index 3f4fa81..c155479 100644
>> --- a/fs/cifs/cifsproto.h
>> +++ b/fs/cifs/cifsproto.h
>> @@ -367,7 +367,7 @@ extern int cifs_verify_signature(struct smb_hdr *,
>> extern int cifs_calculate_session_key(struct session_key *key, const char *rn,
>> const char *pass);
>> extern void CalcNTLMv2_response(const struct cifsSesInfo *, char *);
>> -extern void setup_ntlmv2_rsp(struct cifsSesInfo *, char *,
>> +extern int setup_ntlmv2_rsp(struct cifsSesInfo *, char *,
>> const struct nls_table *);
>> #ifdef CONFIG_CIFS_WEAK_PW_HASH
>> extern void calc_lanman_hash(const char *password, const char *cryptkey,
>> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
>> index c65c341..13c854e 100644
>> --- a/fs/cifs/cifssmb.c
>> +++ b/fs/cifs/cifssmb.c
>> @@ -603,13 +603,15 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
>> rc = 0;
>> else
>> rc = -EINVAL;
>> -
>> - if (server->sec_kerberos || server->sec_mskerberos)
>> - server->secType = Kerberos;
>> - else if (server->sec_ntlmssp)
>> - server->secType = RawNTLMSSP;
>> - else
>> - rc = -EOPNOTSUPP;
>> + if (server->secType == Kerberos) {
>> + if (!server->sec_kerberos &&
>> + !server->sec_mskerberos)
>> + rc = -EOPNOTSUPP;
>> + } else if (server->secType == RawNTLMSSP) {
>> + if (!server->sec_ntlmssp)
>> + rc = -EOPNOTSUPP;
>> + } else
>> + rc = -EOPNOTSUPP;
>> }
>> } else
>> server->capabilities &= ~CAP_EXTENDED_SECURITY;
>> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
>> index 67dad54..f8891a2 100644
>> --- a/fs/cifs/connect.c
>> +++ b/fs/cifs/connect.c
>> @@ -1740,6 +1740,8 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
>> if (ses == NULL)
>> goto get_ses_fail;
>>
>> + ses->tilen = 0;
>> + ses->tiblob = NULL;
>> /* new SMB session uses our server ref */
>> ses->server = server;
>> if (server->addr.sockAddr6.sin6_family == AF_INET6)
>> diff --git a/fs/cifs/ntlmssp.h b/fs/cifs/ntlmssp.h
>> index 49c9a4e..5d52e4a 100644
>> --- a/fs/cifs/ntlmssp.h
>> +++ b/fs/cifs/ntlmssp.h
>> @@ -61,6 +61,21 @@
>> #define NTLMSSP_NEGOTIATE_KEY_XCH 0x40000000
>> #define NTLMSSP_NEGOTIATE_56 0x80000000
>>
>> +/* Define AV Pair Field IDs */
>> +enum av_field_type {
>> + NTLMSSP_AV_EOL = 0,
>> + NTLMSSP_AV_NB_COMPUTER_NAME,
>> + NTLMSSP_AV_NB_DOMAIN_NAME,
>> + NTLMSSP_AV_DNS_COMPUTER_NAME,
>> + NTLMSSP_AV_DNS_DOMAIN_NAME,
>> + NTLMSSP_AV_DNS_TREE_NAME,
>> + NTLMSSP_AV_FLAGS,
>> + NTLMSSP_AV_TIMESTAMP,
>> + NTLMSSP_AV_RESTRICTION,
>> + NTLMSSP_AV_TARGET_NAME,
>> + NTLMSSP_AV_CHANNEL_BINDINGS
>> +};
>> +
>> /* Although typedefs are not commonly used for structure definitions */
>> /* in the Linux kernel, in this particular case they are useful */
>> /* to more closely match the standards document for NTLMSSP from */
>
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
>
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