cifs: fetch credentials out of keyring for non-krb5 auth multiuser mounts

Fix up multiuser mounts to set the secType and set the username and
password from the key payload in the vol info for non-krb5 auth types.

Look for a key of type "secret" with a description of
"cifs:a:<server address>" or "cifs:d:<domainname>". If that's found,
then scrape the username and password out of the key payload and use
that to create a new user session.

Finally, don't have the code enforce krb5 auth on multiuser mounts,
but do require a kernel with keys support.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 165 insertions, 10 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index b952a21e917..28f23c03da5 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -38,6 +38,7 @@
 #include <asm/processor.h>
 #include <linux/inet.h>
 #include <linux/module.h>
+#include <keys/user-type.h>
 #include <net/ipv6.h>
 #include "cifspdu.h"
 #include "cifsglob.h"
@@ -1594,11 +1595,14 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
                 }
         }
 
-        if (vol->multiuser && !(vol->secFlg & CIFSSEC_MAY_KRB5)) {
-                cERROR(1, "Multiuser mounts currently require krb5 "
-                          "authentication!");
+#ifndef CONFIG_KEYS
+        /* Muliuser mounts require CONFIG_KEYS support */
+        if (vol->multiuser) {
+                cERROR(1, "Multiuser mounts require kernels with "
+                          "CONFIG_KEYS enabled.");
                 goto cifs_parse_mount_err;
         }
+#endif
 
         if (vol->UNCip == NULL)
                 vol->UNCip = &vol->UNC[2];
@@ -2061,6 +2065,132 @@ cifs_put_smb_ses(struct cifs_ses *ses)
         cifs_put_tcp_session(server);
 }
 
+#ifdef CONFIG_KEYS
+
+/* strlen("cifs:a:") + INET6_ADDRSTRLEN + 1 */
+#define CIFSCREDS_DESC_SIZE (7 + INET6_ADDRSTRLEN + 1)
+
+/* Populate username and pw fields from keyring if possible */
+static int
+cifs_set_cifscreds(struct smb_vol *vol, struct cifs_ses *ses)
+{
+        int rc = 0;
+        char *desc, *delim, *payload;
+        ssize_t len;
+        struct key *key;
+        struct TCP_Server_Info *server = ses->server;
+        struct sockaddr_in *sa;
+        struct sockaddr_in6 *sa6;
+        struct user_key_payload *upayload;
+
+        desc = kmalloc(CIFSCREDS_DESC_SIZE, GFP_KERNEL);
+        if (!desc)
+                return -ENOMEM;
+
+        /* try to find an address key first */
+        switch (server->dstaddr.ss_family) {
+        case AF_INET:
+                sa = (struct sockaddr_in *)&server->dstaddr;
+                sprintf(desc, "cifs:a:%pI4", &sa->sin_addr.s_addr);
+                break;
+        case AF_INET6:
+                sa6 = (struct sockaddr_in6 *)&server->dstaddr;
+                sprintf(desc, "cifs:a:%pI6c", &sa6->sin6_addr.s6_addr);
+                break;
+        default:
+                cFYI(1, "Bad ss_family (%hu)", server->dstaddr.ss_family);
+                rc = -EINVAL;
+                goto out_err;
+        }
+
+        cFYI(1, "%s: desc=%s", __func__, desc);
+        key = request_key(&key_type_logon, desc, "");
+        if (IS_ERR(key)) {
+                if (!ses->domainName) {
+                        cFYI(1, "domainName is NULL");
+                        rc = PTR_ERR(key);
+                        goto out_err;
+                }
+
+                /* didn't work, try to find a domain key */
+                sprintf(desc, "cifs:d:%s", ses->domainName);
+                cFYI(1, "%s: desc=%s", __func__, desc);
+                key = request_key(&key_type_logon, desc, "");
+                if (IS_ERR(key)) {
+                        rc = PTR_ERR(key);
+                        goto out_err;
+                }
+        }
+
+        down_read(&key->sem);
+        upayload = key->payload.data;
+        if (IS_ERR_OR_NULL(upayload)) {
+                rc = PTR_ERR(key);
+                goto out_key_put;
+        }
+
+        /* find first : in payload */
+        payload = (char *)upayload->data;
+        delim = strnchr(payload, upayload->datalen, ':');
+        cFYI(1, "payload=%s", payload);
+        if (!delim) {
+                cFYI(1, "Unable to find ':' in payload (datalen=%d)",
+                                upayload->datalen);
+                rc = -EINVAL;
+                goto out_key_put;
+        }
+
+        len = delim - payload;
+        if (len > MAX_USERNAME_SIZE || len <= 0) {
+                cFYI(1, "Bad value from username search (len=%ld)", len);
+                rc = -EINVAL;
+                goto out_key_put;
+        }
+
+        vol->username = kstrndup(payload, len, GFP_KERNEL);
+        if (!vol->username) {
+                cFYI(1, "Unable to allocate %ld bytes for username", len);
+                rc = -ENOMEM;
+                goto out_key_put;
+        }
+        cFYI(1, "%s: username=%s", __func__, vol->username);
+
+        len = key->datalen - (len + 1);
+        if (len > MAX_PASSWORD_SIZE || len <= 0) {
+                cFYI(1, "Bad len for password search (len=%ld)", len);
+                rc = -EINVAL;
+                kfree(vol->username);
+                vol->username = NULL;
+                goto out_key_put;
+        }
+
+        ++delim;
+        vol->password = kstrndup(delim, len, GFP_KERNEL);
+        if (!vol->password) {
+                cFYI(1, "Unable to allocate %ld bytes for password", len);
+                rc = -ENOMEM;
+                kfree(vol->username);
+                vol->username = NULL;
+                goto out_key_put;
+        }
+
+out_key_put:
+        up_read(&key->sem);
+        key_put(key);
+out_err:
+        kfree(desc);
+        cFYI(1, "%s: returning %d", __func__, rc);
+        return rc;
+}
+#else /* ! CONFIG_KEYS */
+static inline int
+cifs_set_cifscreds(struct smb_vol *vol __attribute__((unused)),
+                   struct cifs_ses *ses __attribute__((unused)))
+{
+        return -ENOSYS;
+}
+#endif /* CONFIG_KEYS */
+
 static bool warned_on_ntlm;  /* globals init to false automatically */
 
 static struct cifs_ses *
@@ -3693,16 +3823,38 @@ int cifs_setup_session(unsigned int xid, struct cifs_ses *ses,
         return rc;
 }
 
+static int
+cifs_set_vol_auth(struct smb_vol *vol, struct cifs_ses *ses)
+{
+        switch (ses->server->secType) {
+        case Kerberos:
+                vol->secFlg = CIFSSEC_MUST_KRB5;
+                return 0;
+        case NTLMv2:
+                vol->secFlg = CIFSSEC_MUST_NTLMV2;
+                break;
+        case NTLM:
+                vol->secFlg = CIFSSEC_MUST_NTLM;
+                break;
+        case RawNTLMSSP:
+                vol->secFlg = CIFSSEC_MUST_NTLMSSP;
+                break;
+        case LANMAN:
+                vol->secFlg = CIFSSEC_MUST_LANMAN;
+                break;
+        }
+
+        return cifs_set_cifscreds(vol, ses);
+}
+
 static struct cifs_tcon *
 cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
 {
+        int rc;
         struct cifs_tcon *master_tcon = cifs_sb_master_tcon(cifs_sb);
         struct cifs_ses *ses;
         struct cifs_tcon *tcon = NULL;
         struct smb_vol *vol_info;
-        char username[28]; /* big enough for "krb50x" + hex of ULONG_MAX 6+16 */
-                           /* We used to have this as MAX_USERNAME which is   */
-                           /* way too big now (256 instead of 32) */
 
         vol_info = kzalloc(sizeof(*vol_info), GFP_KERNEL);
         if (vol_info == NULL) {
@@ -3710,8 +3862,6 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
                 goto out;
         }
 
-        snprintf(username, sizeof(username), "krb50x%x", fsuid);
-        vol_info->username = username;
         vol_info->local_nls = cifs_sb->local_nls;
         vol_info->linux_uid = fsuid;
         vol_info->cred_uid = fsuid;
@@ -3721,8 +3871,11 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
         vol_info->local_lease = master_tcon->local_lease;
         vol_info->no_linux_ext = !master_tcon->unix_ext;
 
-        /* FIXME: allow for other secFlg settings */
-        vol_info->secFlg = CIFSSEC_MUST_KRB5;
+        rc = cifs_set_vol_auth(vol_info, master_tcon->ses);
+        if (rc) {
+                tcon = ERR_PTR(rc);
+                goto out;
+        }
 
         /* get a reference for the same TCP session */
         spin_lock(&cifs_tcp_ses_lock);
@@ -3745,6 +3898,8 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
         if (ses->capabilities & CAP_UNIX)
                 reset_cifs_unix_caps(0, tcon, NULL, vol_info);
 out:
+        kfree(vol_info->username);
+        kfree(vol_info->password);
         kfree(vol_info);
 
         return tcon;