cifs.upcall: use pid value from kernel to determine KRB5CCNAME to use

If the kernel sends the upcall a pid of the requesting process, we can
open that process' /proc/<pid>/environ file and scrape the KRB5CCNAME
value out of it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/client/cifs.upcall.c b/client/cifs.upcall.c
index 4110de35fde43dacc0eaa6300bd08922fb90223a..e592a4f7c52a213338314748ca89748ebc52d0cf 100644 (file)
--- a/client/cifs.upcall.c
+++ b/client/cifs.upcall.c
@@ -1,6 +1,7 @@
 /*
 * CIFS user-space helper.
 * Copyright (C) Igor Mammedov (niallain@gmail.com) 2007
 /*
 * CIFS user-space helper.
 * Copyright (C) Igor Mammedov (niallain@gmail.com) 2007

+* Copyright (C) Jeff Layton (jlayton@redhat.com) 2009

 *
 * Used by /sbin/request-key for handling
 * cifs upcall for kerberos authorization of access to share and
 *
 * Used by /sbin/request-key for handling
 * cifs upcall for kerberos authorization of access to share and


@@ -37,6 +38,54 @@ typedef enum _secType {
        MS_KRB5
 } secType_t;
 
        MS_KRB5
 } secType_t;
 

+/*
+ * given a process ID, get the value of the KRB5CCNAME environment variable
+ * in the context of that process. On error, just return NULL.
+ */
+static char *
+get_krb5_ccname(pid_t pid)
+{
+       int fd;
+       ssize_t len, left;
+
+       /*
+        * FIXME: sysconf for ARG_MAX instead? Kernel seems to be limited to a
+        * page however, so it may not matter.
+        */
+       char buf[4096];
+       char *p, *value = NULL;
+       
+       buf[4095] = '\0';
+       snprintf(buf, 4095, "/proc/%d/environ", pid);
+       fd = open(buf, O_RDONLY);
+       if (fd < 0)
+               return NULL;
+
+       /* FIXME: don't assume that we get it all in the first read? */
+       len = read(fd, buf, 4096);
+       close(fd);
+       if (len < 0)
+               return NULL;
+
+       left = len;
+       p = buf;
+
+       /* can't have valid KRB5CCNAME if there are < 13 bytes left */
+       while (left > 12) {
+               if (strncmp("KRB5CCNAME=", p, 11)) {
+                       p += strnlen(p, left);
+                       ++p;
+                       left = buf + len - p;
+                       continue;
+               }
+               p += 11;
+               left -= 11;
+               value = strndup(p, left);
+               break;
+       }
+       return value;
+}
+

 /*
  * Prepares AP-REQ data for mechToken and gets session key
  * Uses credentials from cache. It will not ask for password
 /*
  * Prepares AP-REQ data for mechToken and gets session key
  * Uses credentials from cache. It will not ask for password


@@ -58,15 +107,15 @@ typedef enum _secType {
  * ret: 0 - success, others - failure
 */
 static int
  * ret: 0 - success, others - failure
 */
 static int

-handle_krb5_mech(const char *oid, const char *principal,
-                    DATA_BLOB * secblob, DATA_BLOB * sess_key)
+handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
+                DATA_BLOB *sess_key, const char *ccname)

 {
        int retval;
        DATA_BLOB tkt, tkt_wrapped;
 
        /* get a kerberos ticket for the service and extract the session key */
 {
        int retval;
        DATA_BLOB tkt, tkt_wrapped;
 
        /* get a kerberos ticket for the service and extract the session key */

-       retval = cli_krb5_get_ticket(principal, 0,
-                                    &tkt, sess_key, 0, NULL, NULL);
+       retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname,
+                                    NULL);

 
        if (retval)
                return retval;
 
        if (retval)
                return retval;


@@ -88,11 +137,12 @@ handle_krb5_mech(const char *oid, const char *principal,
 #define DKD_HAVE_IPV4          8
 #define DKD_HAVE_IPV6          16
 #define DKD_HAVE_UID           32
 #define DKD_HAVE_IPV4          8
 #define DKD_HAVE_IPV6          16
 #define DKD_HAVE_UID           32

+#define DKD_HAVE_PID           64

 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 
 static int
 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
 
 static int

-decode_key_description(const char *desc, int *ver, secType_t * sec,
-                          char **hostname, uid_t * uid)
+decode_key_description(const char *desc, int *ver, secType_t *sec,
+                          char **hostname, uid_t *uid, pid_t *pid)

 {
        int retval = 0;
        char *pos;
 {
        int retval = 0;
        char *pos;


@@ -117,6 +167,16 @@ decode_key_description(const char *desc, int *ver, secType_t * sec,
                        /* BB: do we need it if we have hostname already? */
                } else if (strncmp(tkn, "ipv6=", 5) == 0) {
                        /* BB: do we need it if we have hostname already? */
                        /* BB: do we need it if we have hostname already? */
                } else if (strncmp(tkn, "ipv6=", 5) == 0) {
                        /* BB: do we need it if we have hostname already? */

+               } else if (strncmp(tkn, "pid=", 4) == 0) {
+                       errno = 0;
+                       *pid = strtol(tkn + 4, NULL, 0);
+                       if (errno != 0) {
+                               syslog(LOG_WARNING, "Invalid pid format: %s",
+                                      strerror(errno));
+                               return 1;
+                       } else {
+                               retval |= DKD_HAVE_PID;
+                       }

                } else if (strncmp(tkn, "sec=", 4) == 0) {
                        if (strncmp(tkn + 4, "krb5", 4) == 0) {
                                retval |= DKD_HAVE_SEC;
                } else if (strncmp(tkn, "sec=", 4) == 0) {
                        if (strncmp(tkn + 4, "krb5", 4) == 0) {
                                retval |= DKD_HAVE_SEC;


@@ -224,9 +284,10 @@ int main(const int argc, char *const argv[])
        size_t datalen;
        long rc = 1;
        uid_t uid = 0;
        size_t datalen;
        long rc = 1;
        uid_t uid = 0;

+       pid_t pid = 0;

        int kernel_upcall_version = 0;
        int c, use_cifs_service_prefix = 0;
        int kernel_upcall_version = 0;
        int c, use_cifs_service_prefix = 0;

-       char *buf, *hostname = NULL;
+       char *buf, *ccname = NULL, *hostname = NULL;

        const char *oid;
 
        openlog(prog, 0, LOG_DAEMON);
        const char *oid;
 
        openlog(prog, 0, LOG_DAEMON);


@@ -278,7 +339,7 @@ int main(const int argc, char *const argv[])
        }
 
        rc = decode_key_description(buf, &kernel_upcall_version, &sectype,
        }
 
        rc = decode_key_description(buf, &kernel_upcall_version, &sectype,

-                                   &hostname, &uid);
+                                   &hostname, &uid, &pid);

        if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
                syslog(LOG_WARNING,
                       "unable to get from description necessary params");
        if ((rc & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
                syslog(LOG_WARNING,
                       "unable to get from description necessary params");


@@ -296,6 +357,9 @@ int main(const int argc, char *const argv[])
                goto out;
        }
 
                goto out;
        }
 

+       if (rc & DKD_HAVE_PID)
+               ccname = get_krb5_ccname(pid);
+

        if (rc & DKD_HAVE_UID) {
                rc = setuid(uid);
                if (rc == -1) {
        if (rc & DKD_HAVE_UID) {
                rc = setuid(uid);
                if (rc == -1) {


@@ -304,9 +368,6 @@ int main(const int argc, char *const argv[])
                }
        }
 
                }
        }
 

-       /* BB: someday upcall SPNEGO blob could be checked here to decide
-        * what mech to use */
-

        // do mech specific authorization
        switch (sectype) {
        case MS_KRB5:
        // do mech specific authorization
        switch (sectype) {
        case MS_KRB5:


@@ -333,7 +394,8 @@ int main(const int argc, char *const argv[])
                        else
                                oid = OID_KERBEROS5;
 
                        else
                                oid = OID_KERBEROS5;
 

-                       rc = handle_krb5_mech(oid, princ, &secblob, &sess_key);
+                       rc = handle_krb5_mech(oid, princ, &secblob, &sess_key,
+                                             ccname);

                        SAFE_FREE(princ);
                        break;
                }
                        SAFE_FREE(princ);
                        break;
                }


@@ -385,6 +447,7 @@ out:
                keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
        data_blob_free(&secblob);
        data_blob_free(&sess_key);
                keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
        data_blob_free(&secblob);
        data_blob_free(&sess_key);

+       SAFE_FREE(ccname);

        SAFE_FREE(hostname);
        SAFE_FREE(keydata);
        return rc;
        SAFE_FREE(hostname);
        SAFE_FREE(keydata);
        return rc;