path: root/proxy/src/mechglue/gpp_creds.c

/*
   GSS-PROXY

   Copyright (C) 2012 Red Hat, Inc.
   Copyright (C) 2012 Simo Sorce <simo.sorce@redhat.com>

   Permission is hereby granted, free of charge, to any person obtaining a
   copy of this software and associated documentation files (the "Software"),
   to deal in the Software without restriction, including without limitation
   the rights to use, copy, modify, merge, publish, distribute, sublicense,
   and/or sell copies of the Software, and to permit persons to whom the
   Software is furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   DEALINGS IN THE SOFTWARE.
*/

#include "gss_plugin.h"
#include <gssapi/gssapi_krb5.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>

static OM_uint32 get_local_def_creds(OM_uint32 *minor_status,
                                     struct gpp_name_handle *name,
                                     gss_cred_usage_t cred_usage,
                                     struct gpp_cred_handle *cred_handle)
{
    gss_OID_set interposed_mechs = GSS_C_NO_OID_SET;
    gss_OID_set special_mechs = GSS_C_NO_OID_SET;
    OM_uint32 maj, min;

    maj = GSS_S_FAILURE;
    min = 0;

    interposed_mechs = gss_mech_interposer((gss_OID)&gssproxy_mech_interposer);
    if (interposed_mechs == GSS_C_NO_OID_SET) {
        goto done;
    }
    special_mechs = gpp_special_available_mechs(interposed_mechs);
    if (special_mechs == GSS_C_NO_OID_SET) {
        goto done;
    }

    maj = gss_acquire_cred(&min, name ? name->local : NULL, 0, special_mechs,
                           cred_usage, &cred_handle->local, NULL, NULL);
done:
    *minor_status = min;
    (void)gss_release_oid_set(&min, &special_mechs);
    (void)gss_release_oid_set(&min, &interposed_mechs);
    return maj;
}

OM_uint32 gppint_get_def_creds(OM_uint32 *minor_status,
                               enum gpp_behavior behavior,
                               struct gpp_name_handle *name,
                               gss_cred_usage_t cred_usage,
                               struct gpp_cred_handle **cred_handle)
{
    struct gpp_cred_handle *cred;
    OM_uint32 tmaj = GSS_S_COMPLETE;
    OM_uint32 tmin = 0;
    OM_uint32 maj = GSS_S_FAILURE;
    OM_uint32 min = 0;

    cred = calloc(1, sizeof(struct gpp_cred_handle));
    if (!cred) {
        min = ENOMEM;
        goto done;
    }

    /* See if we should try local first */
    if (behavior == GPP_LOCAL_ONLY || behavior == GPP_LOCAL_FIRST) {

        maj = get_local_def_creds(&min, name, cred_usage, cred);
        if (maj != GSS_S_NO_CRED || behavior != GPP_LOCAL_FIRST) {
            goto done;
        }

        /* not successful, save actual local error if remote fallback fails */
        tmaj = maj;
        tmin = min;
    }

    /* Then try with remote */
    if (behavior == GPP_REMOTE_ONLY || behavior == GPP_REMOTE_FIRST) {

        maj = gpm_acquire_cred(&min,
                               NULL, 0, NULL, cred_usage,
                               &cred->remote, NULL, NULL);

        if (maj == GSS_S_COMPLETE || behavior == GPP_REMOTE_ONLY) {
            goto done;
        }

        /* So remote failed, but we can fallback to local, try that */
        maj = get_local_def_creds(&min, name, cred_usage, cred);
    }

done:
    if (maj != GSS_S_COMPLETE && tmaj != GSS_S_COMPLETE) {
        maj = tmaj;
        min = tmin;
    }
    *minor_status = min;
    if (maj != GSS_S_COMPLETE) {
        gssi_release_cred(&min, (gss_cred_id_t *)&cred);
    }
    *cred_handle = cred;
    return maj;
}

OM_uint32 gssi_inquire_cred(OM_uint32 *minor_status,
                            gss_cred_id_t cred_handle,
                            gss_name_t *name,
                            OM_uint32 *lifetime,
                            gss_cred_usage_t *cred_usage,
                            gss_OID_set *mechanisms)
{
    struct gpp_cred_handle *cred = NULL;
    struct gpp_name_handle *gpname = NULL;
    OM_uint32 maj, min;

    GSSI_TRACE();

    if (cred_handle == GSS_C_NO_CREDENTIAL) {
        maj = gppint_get_def_creds(&min, gpp_get_behavior(), NULL,
                                   GSS_C_INITIATE, &cred);
        if (maj != GSS_S_COMPLETE) {
            goto done;
        }
    } else {
        cred = (struct gpp_cred_handle *)cred_handle;
    }

    if (name) {
        gpname = calloc(1, sizeof(struct gpp_name_handle));
        if (!gpname) {
            min = ENOMEM;
            maj = GSS_S_FAILURE;
            goto done;
        }
    }

    if (cred->local) {
        maj = gss_inquire_cred(&min, cred->local,
                               gpname ? &gpname->local : NULL,
                               lifetime, cred_usage, mechanisms);
    } else if (cred->remote) {
        maj = gpm_inquire_cred(&min, cred->remote,
                               gpname ? &gpname->remote : NULL,
                               lifetime, cred_usage, mechanisms);
    } else {
        min = 0;
        maj = GSS_S_FAILURE;
    }

done:
    *minor_status = gpp_map_error(min);
    if (cred_handle == GSS_C_NO_CREDENTIAL) {
        gssi_release_cred(&min, (gss_cred_id_t*)&cred);
    }
    if (name && maj == GSS_S_COMPLETE) {
        *name = (gss_name_t)gpname;
    } else {
        free(gpname);
    }
    return maj;
}

OM_uint32 gssi_inquire_cred_by_mech(OM_uint32 *minor_status,
                                    gss_cred_id_t cred_handle,
                                    gss_OID mech_type,
                                    gss_name_t *name,
                                    OM_uint32 *initiator_lifetime,
                                    OM_uint32 *acceptor_lifetime,
                                    gss_cred_usage_t *cred_usage)
{
    struct gpp_cred_handle *cred = NULL;
    struct gpp_name_handle *gpname = NULL;
    OM_uint32 maj, min;

    GSSI_TRACE();

    if (cred_handle == GSS_C_NO_CREDENTIAL) {
        maj = gppint_get_def_creds(&min, gpp_get_behavior(), NULL,
                                   GSS_C_INITIATE, &cred);
        if (maj != GSS_S_COMPLETE) {
            goto done;
        }
    } else {
        cred = (struct gpp_cred_handle *)cred_handle;
    }

    if (name) {
        gpname = calloc(1, sizeof(struct gpp_name_handle));
        if (!gpname) {
            min = ENOMEM;
            maj = GSS_S_FAILURE;
            goto done;
        }
    }

    if (cred->local) {
        maj = gss_inquire_cred_by_mech(&min, cred->local,
                                       gpp_special_mech(mech_type),
                                       gpname ? &gpname->local : NULL,
                                       initiator_lifetime, acceptor_lifetime,
                                       cred_usage);
    } else if (cred->remote) {
        maj = gpm_inquire_cred_by_mech(&min, cred->remote,
                                       gpp_unspecial_mech(mech_type),
                                       gpname ? &gpname->remote : NULL,
                                       initiator_lifetime, acceptor_lifetime,
                                       cred_usage);
    } else {
        min = 0;
        maj = GSS_S_FAILURE;
    }

done:
    *minor_status = gpp_map_error(min);
    if (cred_handle == GSS_C_NO_CREDENTIAL) {
        gssi_release_cred(&min, (gss_cred_id_t*)&cred);
    }
    if (name && maj == GSS_S_COMPLETE) {
        *name = (gss_name_t)gpname;
    } else {
        free(gpname);
    }
    return maj;
}

OM_uint32 gssi_inquire_cred_by_oid(OM_uint32 *minor_status,
	                           const gss_cred_id_t cred_handle,
	                           const gss_OID desired_object,
	                           gss_buffer_set_t *data_set)
{
    struct gpp_cred_handle *cred = NULL;
    OM_uint32 maj, min;

    GSSI_TRACE();

    *minor_status = 0;
    if (cred_handle == GSS_C_NO_CREDENTIAL) {
        return GSS_S_CALL_INACCESSIBLE_READ;
    }
    cred = (struct gpp_cred_handle *)cred_handle;

    /* NOTE: For now we can do this only for local credentials,
     * but as far as I know there is no real oid defined, at least
     * for the krb5 mechs, so this may be a mooot point */
    if (!cred->local) {
        return GSS_S_UNAVAILABLE;
    }

    maj = gss_inquire_cred_by_oid(&min, cred->local, desired_object, data_set);

    *minor_status = gpp_map_error(min);
    return maj;
}

#define GSS_KRB5_SET_ALLOWABLE_ENCTYPES_OID_LENGTH 11
#define GSS_KRB5_SET_ALLOWABLE_ENCTYPES_OID "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x04"

const gss_OID_desc gpp_allowed_enctypes_oid = {
    .length = GSS_KRB5_SET_ALLOWABLE_ENCTYPES_OID_LENGTH,
    .elements = GSS_KRB5_SET_ALLOWABLE_ENCTYPES_OID
};

struct gpp_allowable_enctypes {
    uint32_t num_ktypes;
    krb5_enctype *ktypes;
};

#define KRB5_SET_ALLOWED_ENCTYPE "krb5_set_allowed_enctype_values"

static uint32_t gpp_set_opt_allowable_entypes(uint32_t *min, gssx_cred *cred,
                                              const gss_buffer_t value)
{
    struct gpp_allowable_enctypes *ae;
    struct gssx_cred_element *ce = NULL;
    gss_OID_desc mech;
    gssx_option *to;
    gssx_buffer *tb;
    int i;

    /* Find the first element that matches one of the krb related OIDs */
    for (i = 0; i < cred->elements.elements_len; i++) {
        gp_conv_gssx_to_oid(&cred->elements.elements_val[i].mech, &mech);
        if (gpp_is_krb5_oid(&mech)) {
            ce = &cred->elements.elements_val[i];
            break;
        }
    }

    if (!ce) {
        *min = EINVAL;
        return GSS_S_FAILURE;
    }

    to = realloc(ce->options.options_val,
                 sizeof(gssx_option) * (ce->options.options_len + 1));
    if (!to) {
        *min = ENOMEM;
        return GSS_S_FAILURE;
    }
    ce->options.options_val = to;
    i = ce->options.options_len;

    tb = &ce->options.options_val[i].option;
    tb->octet_string_len = sizeof(KRB5_SET_ALLOWED_ENCTYPE);
    tb->octet_string_val = strdup(KRB5_SET_ALLOWED_ENCTYPE);
    if (!tb->octet_string_val) {
        *min = ENOMEM;
        return GSS_S_FAILURE;
    }

    ae = (struct gpp_allowable_enctypes *)value->value;
    tb = &ce->options.options_val[i].value;
    tb->octet_string_len = sizeof(krb5_enctype) * ae->num_ktypes;
    tb->octet_string_val = malloc(tb->octet_string_len);
    if (!tb->octet_string_val) {
        *min = ENOMEM;
        return GSS_S_FAILURE;
    }
    memcpy(tb->octet_string_val, ae->ktypes, tb->octet_string_len);

    ce->options.options_len++;

    *min = 0;
    return GSS_S_COMPLETE;
}

static uint32_t gpp_remote_options(uint32_t *min, gssx_cred *cred,
                                   const gss_OID desired_object,
                                   const gss_buffer_t value)
{
    uint32_t maj  = GSS_S_UNAVAILABLE;

    if (gss_oid_equal(&gpp_allowed_enctypes_oid, desired_object)) {
        maj = gpp_set_opt_allowable_entypes(min, cred, value);
    }

    return maj;
}

OM_uint32 gssi_set_cred_option(OM_uint32 *minor_status,
                               gss_cred_id_t *cred_handle,
                               const gss_OID desired_object,
                               const gss_buffer_t value)
{
    struct gpp_cred_handle *cred = NULL;
    OM_uint32 maj, min;

    GSSI_TRACE();

    *minor_status = 0;
    if (*cred_handle == GSS_C_NO_CREDENTIAL) {
        return GSS_S_CALL_INACCESSIBLE_READ;
    }
    cred = (struct gpp_cred_handle *)*cred_handle;

    /* NOTE: For now we can do this only for known objects
     * or local credentials */
    if (cred->remote) {
        return gpp_remote_options(minor_status, cred->remote,
                                  desired_object, value);
    }
    if (!cred->local) {
        return GSS_S_UNAVAILABLE;
    }

    maj = gss_set_cred_option(&min, &cred->local, desired_object, value);

    *minor_status = gpp_map_error(min);
    return maj;
}

#define GP_CCNAME "GSSPROXYCCNAME"
#define DEFAULT_GP_CCNAME ".gssproxyccache"

#define PWBUFLEN 2048
static char *get_def_ccname(void)
{
    struct passwd pwd, *res = NULL;
    char buffer[PWBUFLEN];
    char *ccname;
    int ret;

    ret = getpwuid_r(geteuid(), &pwd, buffer, PWBUFLEN, &res);
    if (ret || !res) {
        return NULL;
    }
    ret = asprintf(&ccname, "%s/%s", pwd.pw_dir, DEFAULT_GP_CCNAME);
    if (ret == 1) {
        return NULL;
    }
    return ccname;
}

static int file_lock(int fd, size_t len, bool lock)
{
    struct flock l = {
        .l_whence = SEEK_SET,
        .l_start = 0,
        .l_len = len
    };
    int ret;

    if (lock) {
        l.l_type = F_WRLCK;
    } else {
        l.l_type = F_UNLCK;
    }
    errno = 0;
    do {
        ret = fcntl(fd, F_SETLKW, &l);
    } while(ret == -1 && errno == EINTR);

    return ret;
}

#define MAX_CRED_SIZE 1024*1024
static int store_cred(const char *file_name,
                      struct gssx_cred *cred)
{
    /* version 1 */
    int version = 1;
    XDR xdrctx;
    size_t buflen = 0;
    char buffer[MAX_CRED_SIZE];
    uint32_t beint;
    ssize_t len = 0;
    int fd = -1;
    int ret;

    xdrmem_create(&xdrctx, buffer, MAX_CRED_SIZE, XDR_ENCODE);
    if (!xdr_gssx_cred(&xdrctx, cred)) {
        ret = EIO;
        goto done;
    }
    buflen = htobe32(xdr_getpos(&xdrctx));

    ret = EIO;
    fd = open(file_name, O_RDWR|O_CLOEXEC, 0600);
    if (fd != -1) {
        ret = file_lock(fd, MAX_CRED_SIZE, true);
        if (ret == -1) {
            ret = errno;
            goto done;
        }
        beint = htobe32(version);
        len = gp_safe_write(fd, &beint, sizeof(uint32_t));
        if (len != sizeof(uint32_t)) {
            ret = EIO;
            len = 0;
            goto done;
        }
        beint = htobe32(buflen);
        len = gp_safe_write(fd, &beint, sizeof(uint32_t));
        if (len != sizeof(uint32_t)) {
            ret = EIO;
            len = 0;
            goto done;
        }
        len = gp_safe_write(fd, buffer, buflen);
        if (len != buflen) {
            ret = EIO;
            len = 0;
            goto done;
        }

        /* total file length for truncate */
        len += sizeof(uint32_t) * 2;
        ret = 0;
    }

done:
    if (fd != -1) {
        (void)ftruncate(fd, len);
        (void)file_lock(fd, MAX_CRED_SIZE, false);
        (void)close(fd);
    }
    xdr_destroy(&xdrctx);
    return ret;
}

OM_uint32 gssi_store_cred(OM_uint32 *minor_status,
                          const gss_cred_id_t input_cred_handle,
                          gss_cred_usage_t input_usage,
                          const gss_OID desired_mech,
                          OM_uint32 overwrite_cred,
                          OM_uint32 default_cred,
                          gss_OID_set *elements_stored,
                          gss_cred_usage_t *cred_usage_stored)
{
    struct gpp_cred_handle *cred = NULL;
    char *gp_cc_name = NULL;
    OM_uint32 maj, min;

    GSSI_TRACE();

    *minor_status = 0;
    if (input_cred_handle == GSS_C_NO_CREDENTIAL) {
        return GSS_S_CALL_INACCESSIBLE_READ;
    }
    cred = (struct gpp_cred_handle *)input_cred_handle;

    /* NOTE: For now we can do this only for local credentials */
    if (cred->local) {
        maj = gss_store_cred(&min, cred->local, input_usage,
                             gpp_special_mech(desired_mech),
                             overwrite_cred, default_cred,
                             elements_stored, cred_usage_stored);
    } else if (cred->remote) {
        gp_cc_name = strdup(gp_getenv(GP_CCNAME));
        if (!gp_cc_name) {
            gp_cc_name = get_def_ccname();
            if (!gp_cc_name) {
                maj = GSS_S_FAILURE;
                min = ENOMEM;
            }
        }
        min = store_cred(gp_cc_name, cred->remote);
        if (min != 0) {
            maj = GSS_S_FAILURE;
        } else {
            maj = GSS_S_COMPLETE;
        }
    } else {
        return GSS_S_NO_CRED;
    }

    free(gp_cc_name);
    *minor_status = gpp_map_error(min);
    return maj;
}

OM_uint32 gssi_release_cred(OM_uint32 *minor_status,
                            gss_cred_id_t *cred_handle)
{
    struct gpp_cred_handle *cred;
    OM_uint32 maj, min;
    OM_uint32 rmaj = GSS_S_COMPLETE;

    GSSI_TRACE();

    if (*cred_handle == GSS_C_NO_CREDENTIAL) {
        *minor_status = 0;
        return GSS_S_COMPLETE;
    }

    cred = (struct gpp_cred_handle *)*cred_handle;

    if (cred->local) {
        maj = gss_release_cred(&min, &cred->local);
        if (maj != GSS_S_COMPLETE) {
            rmaj = maj;
            *minor_status = gpp_map_error(min);
        }
    }

    if (cred->remote) {
        maj = gpm_release_cred(&min, &cred->remote);
        if (maj && rmaj == GSS_S_COMPLETE) {
            rmaj = maj;
            *minor_status = gpp_map_error(min);
        }
    }

    free(cred);
    *cred_handle = GSS_C_NO_CREDENTIAL;
    return rmaj;
}

OM_uint32 gssi_export_cred(OM_uint32 *minor_status,
                           gss_cred_id_t cred_handle,
                           gss_buffer_t token)
{
    struct gpp_cred_handle *cred;

    GSSI_TRACE();

    cred = (struct gpp_cred_handle *)cred_handle;
    if (!cred) {
        return GSS_S_CALL_INACCESSIBLE_READ;
    }

    /* We do not support exporting creds via the proxy.
     * It's exclusively a local operation for now */
    if (!cred->local) {
        return GSS_S_CRED_UNAVAIL;
    }

    return gss_export_cred(minor_status, cred->local, token);
}

OM_uint32 gssi_import_cred(OM_uint32 *minor_status,
                           gss_buffer_t token,
                           gss_cred_id_t *cred_handle)
{
    GSSI_TRACE();
    return GSS_S_UNAVAILABLE;
}

OM_uint32 gssi_import_cred_by_mech(OM_uint32 *minor_status,
                                   gss_OID mech_type,
                                   gss_buffer_t token,
                                   gss_cred_id_t *cred_handle)
{
    struct gpp_cred_handle *cred;
    gss_buffer_desc wrap_token = {0};
    gss_OID spmech;
    OM_uint32 maj, min = 0;
    uint32_t len;

    GSSI_TRACE();

    cred = calloc(1, sizeof(struct gpp_cred_handle));
    if (!cred) {
        *minor_status = 0;
        return GSS_S_FAILURE;
    }

    /* NOTE: it makes no sense to import a cred remotely atm,
     * so we only handle the local case for now. */
    spmech = gpp_special_mech(mech_type);
    if (spmech == GSS_C_NO_OID) {
        maj = GSS_S_FAILURE;
        goto done;
    }

    wrap_token.length = sizeof(uint32_t) + spmech->length + token->length;
    wrap_token.value = malloc(wrap_token.length);
    if (!wrap_token.value) {
        wrap_token.length = 0;
        maj = GSS_S_FAILURE;
        goto done;
    }

    len = htobe32(wrap_token.length);
    memcpy(wrap_token.value, &len, sizeof(uint32_t));
    memcpy(wrap_token.value + sizeof(uint32_t),
           spmech->elements, spmech->length);
    memcpy(wrap_token.value + sizeof(uint32_t) + spmech->length,
           token->value, token->length);

    maj = gss_import_cred(&min, &wrap_token, &cred->local);

done:
    *minor_status = gpp_map_error(min);
    if (maj == GSS_S_COMPLETE) {
        *cred_handle = (gss_cred_id_t)cred;
    } else {
        free(cred);
    }
    (void)gss_release_buffer(&min, &wrap_token);
    return maj;
}