sss_client: Add common shared memory cache utils

2 files changed, 334 insertions, 0 deletions

diff --git a/src/sss_client/nss_mc.h b/src/sss_client/nss_mc.h
new file mode 100644
index 00000000..35cefe5b
--- /dev/null
+++ b/src/sss_client/nss_mc.h
@@ -0,0 +1,62 @@
+/*
+ * System Security Services Daemon. NSS client interface
+ *
+ * Copyright (C) Simo Sorce 2011
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* NSS interfaces to mmap cache */
+
+#ifndef _NSS_MC_H_
+#define _NSS_MC_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <pwd.h>
+#include "util/mmap_cache.h"
+
+#ifndef HAVE_ERRNO_T
+#define HAVE_ERRNO_T
+typedef int errno_t;
+#endif
+
+/* common stuff */
+struct sss_cli_mc_ctx {
+    bool initialized;
+    int fd;
+
+    uint32_t seed;          /* seed from the tables header */
+
+    void *mmap_base;        /* base address of mmap */
+    size_t mmap_size;       /* total size of mmap */
+
+    uint8_t *data_table;    /* data table address (in mmap) */
+    uint32_t dt_size;       /* size of data table */
+
+    uint32_t *hash_table;   /* hash table address (in mmap) */
+    uint32_t ht_size;       /* size of hash table */
+};
+
+errno_t sss_nss_mc_get_ctx(const char *name, struct sss_cli_mc_ctx *ctx);
+errno_t sss_nss_check_header(struct sss_cli_mc_ctx *ctx);
+uint32_t sss_nss_mc_hash(struct sss_cli_mc_ctx *ctx,
+                         const char *key, size_t len);
+errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx,
+                              uint32_t slot, struct sss_mc_rec **_rec);
+errno_t sss_nss_str_ptr_from_buffer(char **str, void **cookie,
+                                    char *buf, size_t len);
+
+#endif /* _NSS_MC_H_ */
diff --git a/src/sss_client/nss_mc_common.c b/src/sss_client/nss_mc_common.c
new file mode 100644
index 00000000..5391df97
--- /dev/null
+++ b/src/sss_client/nss_mc_common.c
@@ -0,0 +1,272 @@
+/*
+ * System Security Services Daemon. NSS client interface
+ *
+ * Copyright (C) Simo Sorce 2011
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* NSS interfaces to mmap cache */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <stdlib.h>
+#include "nss_mc.h"
+
+/* FIXME: hook up to library destructor to avoid leaks */
+/* FIXME: temporarily open passwd file on our own, later we will probably
+ * use socket passing from the main process */
+/* FIXME: handle name upper/lower casing ? Maybe a flag passed down by
+ * sssd or a flag in sss_mc_header ? per domain ? */
+
+errno_t sss_nss_check_header(struct sss_cli_mc_ctx *ctx)
+{
+    struct sss_mc_header h;
+    int count;
+
+    /* retry barrier protected reading max 5 times then give up */
+    for (count = 5; count > 0; count--) {
+        memcpy(&h, ctx->mmap_base, sizeof(struct sss_mc_header));
+        if (MC_VALID_BARRIER(h.b1) && h.b1 == h.b2) {
+            /* record is consistent so we can proceed */
+            break;
+        }
+    }
+    if (count == 0) {
+        /* couldn't successfully read header we have to give up */
+        return EIO;
+    }
+
+    if (h.major_vno != SSS_MC_MAJOR_VNO ||
+        h.minor_vno != SSS_MC_MINOR_VNO ||
+        h.status == SSS_MC_HEADER_RECYCLED) {
+        return EINVAL;
+    }
+
+    /* first time we check the header, let's fill our own struct */
+    if (ctx->data_table == NULL) {
+        ctx->seed = h.seed;
+        ctx->data_table = MC_PTR_ADD(ctx->mmap_base, h.data_table);
+        ctx->hash_table = MC_PTR_ADD(ctx->mmap_base, h.hash_table);
+        ctx->dt_size = h.dt_size;
+        ctx->ht_size = h.ht_size;
+    } else {
+        if (ctx->seed != h.seed ||
+            ctx->data_table != MC_PTR_ADD(ctx->mmap_base, h.data_table) ||
+            ctx->hash_table != MC_PTR_ADD(ctx->mmap_base, h.hash_table) ||
+            ctx->dt_size != h.dt_size ||
+            ctx->ht_size != h.ht_size) {
+            return EINVAL;
+        }
+    }
+
+    return 0;
+}
+
+errno_t sss_nss_mc_get_ctx(const char *name, struct sss_cli_mc_ctx *ctx)
+{
+    struct stat fdstat;
+    char *file = NULL;
+    char *envval;
+    int ret;
+
+    envval = getenv("_SSS_MC_SPECIAL");
+    if (envval && strcmp(envval, "NO") == 0) {
+        return EPERM;
+    }
+
+    if (ctx->initialized) {
+        ret = sss_nss_check_header(ctx);
+        goto done;
+    }
+
+    ret = asprintf(&file, "%s/%s", SSS_NSS_MCACHE_DIR, name);
+    if (ret == -1) {
+        ret = ENOMEM;
+        goto done;
+    }
+
+    ctx->fd = open(file, O_RDONLY);
+    if (ctx->fd == -1) {
+        ret = EIO;
+        goto done;
+    }
+
+    ret = fstat(ctx->fd, &fdstat);
+    if (ret == -1) {
+        ret = EIO;
+        goto done;
+    }
+
+    if (fdstat.st_size < MC_HEADER_SIZE) {
+        ret = ENOMEM;
+        goto done;
+    }
+    ctx->mmap_size = fdstat.st_size;
+
+    ctx->mmap_base = mmap(NULL, ctx->mmap_size,
+                          PROT_READ, MAP_SHARED, ctx->fd, 0);
+    if (ctx->mmap_base == MAP_FAILED) {
+        ret = ENOMEM;
+        goto done;
+    }
+
+    ret = sss_nss_check_header(ctx);
+    if (ret != 0) {
+        goto done;
+    }
+
+    ctx->initialized = true;
+
+    ret = 0;
+
+done:
+    if (ret) {
+        if ((ctx->mmap_base != NULL) && (ctx->mmap_size != 0)) {
+            munmap(ctx->mmap_base, ctx->mmap_size);
+        }
+        if (ctx->fd != -1) {
+            close(ctx->fd);
+        }
+        memset(ctx, 0, sizeof(struct sss_cli_mc_ctx));
+    }
+    free(file);
+    return ret;
+}
+
+uint32_t sss_nss_mc_hash(struct sss_cli_mc_ctx *ctx,
+                         const char *key, size_t len)
+{
+    return murmurhash3(key, len, ctx->seed) % MC_HT_ELEMS(ctx->ht_size);
+}
+
+errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx,
+                              uint32_t slot, struct sss_mc_rec **_rec)
+{
+    struct sss_mc_rec *rec;
+    void *rec_buf = NULL;
+    size_t buf_size = 0;
+    size_t rec_len;
+    uint32_t b1;
+    uint32_t b2;
+    int count;
+    int ret;
+
+    /* try max 5 times */
+    for (count = 5; count > 0; count--) {
+        rec = MC_SLOT_TO_PTR(ctx->data_table, slot, struct sss_mc_rec);
+
+        /* fetch record length */
+        b1 = rec->b1;
+        __sync_synchronize();
+        rec_len = rec->len;
+        __sync_synchronize();
+        b2 = rec->b1;
+        if (!MC_VALID_BARRIER(b1) || b1 != b2) {
+            /* record is inconsistent, retry */
+            continue;
+        }
+
+        if (rec_len > buf_size) {
+            free(rec_buf);
+            rec_buf = malloc(rec_len);
+            if (!rec_buf) {
+                ret = ENOMEM;
+                goto done;
+            }
+            buf_size = rec_len;
+        }
+        /* we cannot access data directly, we must copy data and then
+         * access the copy */
+        memcpy(rec_buf, rec, rec_len);
+        rec = (struct sss_mc_rec *)rec_buf;
+
+        /* we must check data is consistent again after the copy */
+        if (MC_VALID_BARRIER(rec->b1) &&
+            rec->b1 == rec->b2 &&
+            rec->len == rec_len) {
+            /* record is consistent, use it */
+            break;
+        }
+    }
+    if (count == 0) {
+        /* couldn't successfully read header we have to give up */
+        ret = EIO;
+        goto done;
+    }
+
+    *_rec = rec;
+    ret = 0;
+
+done:
+    if (ret) {
+        free(rec_buf);
+        *_rec = NULL;
+    }
+    return ret;
+}
+
+/*
+ * returns strings froma a buffer.
+ *
+ * Call first time with *cookie set to null, then call again
+ * with the returned cookie.
+ * On the last string the cookie will be reset to null and
+ * all strings will have been returned.
+ * In case the last string is not zero terminated EINVAL is returned.
+ */
+errno_t sss_nss_str_ptr_from_buffer(char **str, void **cookie,
+                                    char *buf, size_t len)
+{
+    char *max = buf + len;
+    char *ret;
+    char *p;
+
+    if (*cookie == NULL) {
+        p = buf;
+    } else {
+        p = *((char **)cookie);
+    }
+
+    ret = p;
+
+    while (p < max) {
+        if (*p == '\0') {
+            break;
+        }
+        p++;
+    }
+    if (p >= max) {
+        return EINVAL;
+    }
+    p++;
+    if (p == max) {
+        *cookie = NULL;
+    } else {
+        *cookie = p;
+    }
+
+    *str = ret;
+    return 0;
+}
+