/*
   GSS-PROXY

   Copyright (C) 2011 Red Hat, Inc.
   Copyright (C) 2011 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 "gssapi_gpm.h"
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

#define FRAGMENT_BIT (1 << 31)

struct gpm_ctx {
    pthread_mutex_t lock;
    int fd;
    int next_xid;
};

/* a single global struct is not particularly efficient,
 * but will do for now */
struct gpm_ctx gpm_global_ctx;

pthread_once_t gpm_init_once_control = PTHREAD_ONCE_INIT;

static void gpm_init_once(void)
{
    pthread_mutexattr_t attr;
    unsigned int seedp;

    pthread_mutexattr_init(&attr);
    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);

    pthread_mutex_init(&gpm_global_ctx.lock, &attr);

    gpm_global_ctx.fd = -1;

    seedp = time(NULL) + getpid() + pthread_self();
    gpm_global_ctx.next_xid = rand_r(&seedp);

    pthread_mutexattr_destroy(&attr);
}

static int get_pipe_name(struct gpm_ctx *gpmctx, char *name)
{
    const char *socket;
    int ret;

    socket = gp_getenv("GSSPROXY_SOCKET");
    if (!socket) {
        socket = GP_SOCKET_NAME;
    }

    ret = snprintf(name, PATH_MAX, "%s", socket);
    if (ret < 0 || ret >= PATH_MAX) {
        return ENAMETOOLONG;
    }

    return 0;
}

static int gpm_open_socket(struct gpm_ctx *gpmctx)
{
    struct sockaddr_un addr = {0};
    char name[PATH_MAX];
    int ret;
    int fd = -1;

    ret = get_pipe_name(gpmctx, name);
    if (ret) {
        return ret;
    }

    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, name, sizeof(addr.sun_path)-1);
    addr.sun_path[sizeof(addr.sun_path)-1] = '\0';

    fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd == -1) {
        ret = errno;
        goto done;
    }

    ret = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
    if (ret == -1) {
        ret = errno;
    }

done:
    if (ret) {
        if (fd != -1) {
            close(fd);
            fd = -1;
        }
    }
    gpmctx->fd = fd;
    return ret;
}

static void gpm_close_socket(struct gpm_ctx *gpmctx)
{
    int ret;

    do {
        ret = close(gpmctx->fd);
        /* in theory we should retry to close() on EINTR,
         * but on same system the fd will be invalid after
         * close() has been called, so closing again may
         * cause a race with another thread that just happend
         * to open an unrelated file descriptor.
         * So until POSIX finally amends language around close()
         * and at least the Linux kernel changes its behavior,
         * it is better to risk a leak than closing an unrelated
         * file descriptor */
        ret = 0;
    } while (ret == EINTR);

    gpmctx->fd = -1;
}

static int gpm_grab_sock(struct gpm_ctx *gpmctx)
{
    int ret;

    ret = pthread_mutex_lock(&gpmctx->lock);
    if (ret) {
        return ret;
    }

    if (gpmctx->fd == -1) {
        ret = gpm_open_socket(gpmctx);
    }

    if (ret) {
        pthread_mutex_unlock(&gpmctx->lock);
    }
    return ret;
}

static int gpm_release_sock(struct gpm_ctx *gpmctx)
{
    return pthread_mutex_unlock(&gpmctx->lock);
}

/* must be called after the lock has been grabbed */
static int gpm_send_buffer(struct gpm_ctx *gpmctx,
                           char *buffer, uint32_t length)
{
    uint32_t size;
    size_t wn;
    size_t pos;
    bool retry;
    int ret;

    if (length > MAX_RPC_SIZE) {
        return EINVAL;
    }

    size = length | FRAGMENT_BIT;
    size = htonl(size);

    retry = false;
    do {
        ret = 0;
        do {
            wn = send(gpmctx->fd, &size, sizeof(uint32_t), MSG_NOSIGNAL);
            if (wn == -1) {
                ret = errno;
            }
        } while (ret == EINTR);
        if (wn != 4) {
            /* reopen and retry once */
            if (retry == false) {
                gpm_close_socket(gpmctx);
                ret = gpm_open_socket(gpmctx);
                if (ret == 0) {
                    retry = true;
                    continue;
                }
            } else {
                ret = EIO;
            }
            goto done;
        }
        retry = false;
    } while (retry);

    pos = 0;
    while (length > pos) {
        wn = send(gpmctx->fd, buffer + pos, length - pos, MSG_NOSIGNAL);
        if (wn == -1) {
            if (errno == EINTR) {
                continue;
            }
            ret = errno;
            goto done;
        }
        pos += wn;
    }

    ret = 0;

done:
    if (ret) {
        /* on errors we can only close the fd and return */
        gpm_close_socket(gpmctx);
    }
    return ret;
}

/* must be called after the lock has been grabbed */
static int gpm_recv_buffer(struct gpm_ctx *gpmctx,
                           char *buffer, uint32_t *length)
{
    uint32_t size;
    size_t rn;
    size_t pos;
    int ret;

    ret = 0;
    do {
        rn = read(gpmctx->fd, &size, sizeof(uint32_t));
        if (rn == -1) {
            ret = errno;
        }
    } while (ret == EINTR);
    if (rn != 4) {
        ret = EIO;
        goto done;
    }

    *length = ntohl(size);
    *length &= ~FRAGMENT_BIT;

    if (*length > MAX_RPC_SIZE) {
        ret = EMSGSIZE;
        goto done;
    }

    pos = 0;
    while (*length > pos) {
        rn = read(gpmctx->fd, buffer + pos, *length - pos);
        if (rn == -1) {
            if (errno == EINTR) {
                continue;
            }
            ret = errno;
            goto done;
        }
        if (rn == 0) {
            ret = EIO;
            goto done;
        }
        pos += rn;
    }

    ret = 0;

done:
    if (ret) {
        /* on errors we can only close the fd and return */
        gpm_close_socket(gpmctx);
    }
    return ret;
}

/* must be called after the lock has been grabbed */
static uint32_t gpm_next_xid(struct gpm_ctx *gpmctx)
{
    uint32_t xid;

    if (gpmctx->next_xid < 0) {
        gpmctx->next_xid = 1;
        xid = 0;
    } else {
        xid = gpmctx->next_xid++;
    }

    return xid;
}

static struct gpm_ctx *gpm_get_ctx(void)
{
    int ret;

    pthread_once(&gpm_init_once_control, gpm_init_once);

    ret = gpm_grab_sock(&gpm_global_ctx);
    if (ret) {
        return NULL;
    }

    return &gpm_global_ctx;
}

static void gpm_release_ctx(struct gpm_ctx *gpmctx)
{
    gpm_release_sock(gpmctx);
}

OM_uint32 gpm_release_buffer(OM_uint32 *minor_status,
                             gss_buffer_t buffer)
{
    if (buffer != GSS_C_NO_BUFFER) {
        if (buffer->value) {
            free(buffer->value);
        }
        buffer->length = 0;
        buffer->value = NULL;
    }
    return GSS_S_COMPLETE;
}

struct gpm_rpc_fn_set {
    xdrproc_t arg_fn;
    xdrproc_t res_fn;
} gpm_xdr_set[] = {
    { /* NULLPROC */
        (xdrproc_t)xdr_void,
        (xdrproc_t)xdr_void,
    },
    { /* GSSX_INDICATE_MECHS */
        (xdrproc_t)xdr_gssx_arg_indicate_mechs,
        (xdrproc_t)xdr_gssx_res_indicate_mechs,
    },
    { /* GSSX_GET_CALL_CONTEXT */
        (xdrproc_t)xdr_gssx_arg_get_call_context,
        (xdrproc_t)xdr_gssx_res_get_call_context,
    },
    { /* GSSX_IMPORT_AND_CANON_NAME */
        (xdrproc_t)xdr_gssx_arg_import_and_canon_name,
        (xdrproc_t)xdr_gssx_res_import_and_canon_name,
    },
    { /* GSSX_EXPORT_CRED */
        (xdrproc_t)xdr_gssx_arg_export_cred,
        (xdrproc_t)xdr_gssx_res_export_cred,
    },
    { /* GSSX_IMPORT_CRED */
        (xdrproc_t)xdr_gssx_arg_import_cred,
        (xdrproc_t)xdr_gssx_res_import_cred,
    },
    { /* GSSX_ACQUIRE_CRED */
        (xdrproc_t)xdr_gssx_arg_acquire_cred,
        (xdrproc_t)xdr_gssx_res_acquire_cred,
    },
    { /* GSSX_STORE_CRED */
        (xdrproc_t)xdr_gssx_arg_store_cred,
        (xdrproc_t)xdr_gssx_res_store_cred,
    },
    { /* GSSX_INIT_SEC_CONTEXT */
        (xdrproc_t)xdr_gssx_arg_init_sec_context,
        (xdrproc_t)xdr_gssx_res_init_sec_context,
    },
    { /* GSSX_ACCEPT_SEC_CONTEXT */
        (xdrproc_t)xdr_gssx_arg_accept_sec_context,
        (xdrproc_t)xdr_gssx_res_accept_sec_context,
    },
    { /* GSSX_RELEASE_HANDLE */
        (xdrproc_t)xdr_gssx_arg_release_handle,
        (xdrproc_t)xdr_gssx_res_release_handle,
    },
    { /* GSSX_GET_MIC */
        (xdrproc_t)xdr_gssx_arg_get_mic,
        (xdrproc_t)xdr_gssx_res_get_mic,
    },
    { /* GSSX_VERIFY */
        (xdrproc_t)xdr_gssx_arg_verify_mic,
        (xdrproc_t)xdr_gssx_res_verify_mic,
    },
    { /* GSSX_WRAP */
        (xdrproc_t)xdr_gssx_arg_wrap,
        (xdrproc_t)xdr_gssx_res_wrap,
    },
    { /* GSSX_UNWRAP */
        (xdrproc_t)xdr_gssx_arg_unwrap,
        (xdrproc_t)xdr_gssx_res_unwrap,
    },
    { /* GSSX_WRAP_SIZE_LIMIT */
        (xdrproc_t)xdr_gssx_arg_wrap_size_limit,
        (xdrproc_t)xdr_gssx_res_wrap_size_limit,
    }
};

int gpm_make_call(int proc, union gp_rpc_arg *arg, union gp_rpc_res *res)
{
    struct gpm_ctx *gpmctx;
    gp_rpc_msg msg;
    XDR xdr_call_ctx;
    XDR xdr_reply_ctx;
    char buffer[MAX_RPC_SIZE];
    uint32_t length;
    uint32_t xid;
    bool xdrok;
    bool sockgrab = false;
    int ret;

    xdrmem_create(&xdr_call_ctx, buffer, MAX_RPC_SIZE, XDR_ENCODE);
    xdrmem_create(&xdr_reply_ctx, buffer, MAX_RPC_SIZE, XDR_DECODE);

    memset(&msg, 0, sizeof(gp_rpc_msg));
    msg.header.type = GP_RPC_CALL;
    msg.header.gp_rpc_msg_union_u.chdr.rpcvers = 2;
    msg.header.gp_rpc_msg_union_u.chdr.prog = GSSPROXY;
    msg.header.gp_rpc_msg_union_u.chdr.vers = GSSPROXYVERS;
    msg.header.gp_rpc_msg_union_u.chdr.proc = proc;
    msg.header.gp_rpc_msg_union_u.chdr.cred.flavor = GP_RPC_AUTH_NONE;
    msg.header.gp_rpc_msg_union_u.chdr.cred.body.body_len = 0;
    msg.header.gp_rpc_msg_union_u.chdr.cred.body.body_val = NULL;
    msg.header.gp_rpc_msg_union_u.chdr.verf.flavor = GP_RPC_AUTH_NONE;
    msg.header.gp_rpc_msg_union_u.chdr.verf.body.body_len = 0;
    msg.header.gp_rpc_msg_union_u.chdr.verf.body.body_val = NULL;

    gpmctx = gpm_get_ctx();
    if (!gpmctx) {
        return EINVAL;
    }

    /* grab the lock for the whole conversation */
    ret = gpm_grab_sock(gpmctx);
    if (ret) {
        goto done;
    }
    sockgrab = true;

    msg.xid = xid = gpm_next_xid(gpmctx);

    /* encode header */
    xdrok = xdr_gp_rpc_msg(&xdr_call_ctx, &msg);
    if (!xdrok) {
        ret = EINVAL;
        goto done;
    }

    /* encode data */
    xdrok = gpm_xdr_set[proc].arg_fn(&xdr_call_ctx, (char *)arg);
    if (!xdrok) {
        ret = EINVAL;
        goto done;
    }

    /* send to proxy */
    ret = gpm_send_buffer(gpmctx, buffer, xdr_getpos(&xdr_call_ctx));
    if (ret) {
        goto done;
    }

    /* receive answer */
    ret = gpm_recv_buffer(gpmctx, buffer, &length);
    if (ret) {
        goto done;
    }

    /* release the lock */
    gpm_release_sock(gpmctx);
    sockgrab = false;

    /* decode header */
    xdrok = xdr_gp_rpc_msg(&xdr_reply_ctx, &msg);
    if (!xdrok) {
        ret = EINVAL;
        goto done;
    }

    if (msg.xid != xid ||
        msg.header.type != GP_RPC_REPLY ||
        msg.header.gp_rpc_msg_union_u.rhdr.status != GP_RPC_MSG_ACCEPTED ||
        msg.header.gp_rpc_msg_union_u.rhdr.gp_rpc_reply_header_u.accepted.reply_data.status != GP_RPC_SUCCESS) {
        ret = EINVAL;
        goto done;
    }

    /* decode answer */
    xdrok = gpm_xdr_set[proc].res_fn(&xdr_reply_ctx, (char *)res);
    if (!xdrok) {
        ret = EINVAL;
    }

done:
    if (sockgrab) {
        gpm_release_sock(gpmctx);
    }
    xdr_free((xdrproc_t)xdr_gp_rpc_msg, (char *)&msg);
    xdr_destroy(&xdr_call_ctx);
    xdr_destroy(&xdr_reply_ctx);
    gpm_release_ctx(gpmctx);
    return ret;
}

void gpm_free_xdrs(int proc, union gp_rpc_arg *arg, union gp_rpc_res *res)
{
    xdr_free(gpm_xdr_set[proc].arg_fn, (char *)arg);
    xdr_free(gpm_xdr_set[proc].res_fn, (char *)res);
}