/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * Berkeley DB 1.85 Shim code to handle blobs.
 */
#include "mcom_db.h"
#include "secitem.h"
#include "nssb64.h"
#include "blapi.h"
#include "secerr.h"

#include "lgdb.h"

/*
 *   Blob block:
 *   Byte 0   CERTDB Version           -+                       -+
 *   Byte 1   certDBEntryTypeBlob       |  BLOB_HEAD_LEN         |
 *   Byte 2   flags (always '0');       |                        |
 *   Byte 3   reserved (always '0');   -+                        |
 *   Byte 4   LSB length                | <--BLOB_LENGTH_START   | BLOB_BUF_LEN
 *   Byte 5       .                     |                        |
 *   Byte 6       .                     | BLOB_LENGTH_LEN        |
 *   Byte 7   MSB length                |                        |
 *   Byte 8   blob_filename   -+       -+  <-- BLOB_NAME_START   |
 *   Byte 9       .            | BLOB_NAME_LEN                   |
 *     .          .            |                                 |
 *   Byte 37      .           -+                                -+
 */
#define DBS_BLOCK_SIZE (16 * 1024)                   /* 16 k */
#define DBS_MAX_ENTRY_SIZE (DBS_BLOCK_SIZE - (2048)) /* 14 k */
#define DBS_CACHE_SIZE DBS_BLOCK_SIZE * 8
#define ROUNDDIV(x, y) (x + (y - 1)) / y
#define BLOB_HEAD_LEN 4
#define BLOB_LENGTH_START BLOB_HEAD_LEN
#define BLOB_LENGTH_LEN 4
#define BLOB_NAME_START BLOB_LENGTH_START + BLOB_LENGTH_LEN
#define BLOB_NAME_LEN 1 + ROUNDDIV(SHA1_LENGTH, 3) * 4 + 1
#define BLOB_BUF_LEN BLOB_HEAD_LEN + BLOB_LENGTH_LEN + BLOB_NAME_LEN

/* a Shim data structure. This data structure has a db built into it. */
typedef struct DBSStr DBS;

struct DBSStr {
    DB db;
    char *blobdir;
    int mode;
    PRBool readOnly;
    char staticBlobArea[BLOB_BUF_LEN];
};

/*
 * return true if the Datablock contains a blobtype
 */
static PRBool
dbs_IsBlob(DBT *blobData)
{
    unsigned char *addr = (unsigned char *)blobData->data;
    if (blobData->size < BLOB_BUF_LEN) {
        return PR_FALSE;
    }
    return addr && ((certDBEntryType)addr[1] == certDBEntryTypeBlob);
}

/*
 * extract the filename in the blob of the real data set.
 * This value is not malloced (does not need to be freed by the caller.
 */
static const char *
dbs_getBlobFileName(DBT *blobData)
{
    char *addr = (char *)blobData->data;

    return &addr[BLOB_NAME_START];
}

/*
 * extract the size of the actual blob from the blob record
 */
static PRUint32
dbs_getBlobSize(DBT *blobData)
{
    unsigned char *addr = (unsigned char *)blobData->data;

    return (PRUint32)(addr[BLOB_LENGTH_START + 3] << 24) |
           (addr[BLOB_LENGTH_START + 2] << 16) |
           (addr[BLOB_LENGTH_START + 1] << 8) |
           addr[BLOB_LENGTH_START];
}

/* We are using base64 data for the filename, but base64 data can include a
 * '/' which is interpreted as a path separator on  many platforms. Replace it
 * with an inocuous '-'. We don't need to convert back because we never actual
 * decode the filename.
 */

static void
dbs_replaceSlash(char *cp, int len)
{
    while (len--) {
        if (*cp == '/')
            *cp = '-';
        cp++;
    }
}

/*
 * create a blob record from a key, data and return it in blobData.
 * NOTE: The data element is static data (keeping with the dbm model).
 */
static void
dbs_mkBlob(DBS *dbsp, const DBT *key, const DBT *data, DBT *blobData)
{
    unsigned char sha1_data[SHA1_LENGTH];
    char *b = dbsp->staticBlobArea;
    PRUint32 length = data->size;
    SECItem sha1Item;

    b[0] = CERT_DB_FILE_VERSION;      /* certdb version number */
    b[1] = (char)certDBEntryTypeBlob; /* type */
    b[2] = 0;                         /* flags */
    b[3] = 0;                         /* reserved */
    b[BLOB_LENGTH_START] = length & 0xff;
    b[BLOB_LENGTH_START + 1] = (length >> 8) & 0xff;
    b[BLOB_LENGTH_START + 2] = (length >> 16) & 0xff;
    b[BLOB_LENGTH_START + 3] = (length >> 24) & 0xff;
    sha1Item.data = sha1_data;
    sha1Item.len = SHA1_LENGTH;
    SHA1_HashBuf(sha1_data, key->data, key->size);
    b[BLOB_NAME_START] = 'b'; /* Make sure we start with a alpha */
    NSSBase64_EncodeItem(NULL, &b[BLOB_NAME_START + 1], BLOB_NAME_LEN - 1, &sha1Item);
    b[BLOB_BUF_LEN - 1] = 0;
    dbs_replaceSlash(&b[BLOB_NAME_START + 1], BLOB_NAME_LEN - 1);
    blobData->data = b;
    blobData->size = BLOB_BUF_LEN;
    return;
}

/*
 * construct a path to the actual blob. The string returned must be
 * freed by the caller with PR_smprintf_free.
 *
 * Note: this file does lots of consistancy checks on the DBT. The
 * routines that call this depend on these checks, so they don't worry
 * about them (success of this routine implies a good blobdata record).
 */
static char *
dbs_getBlobFilePath(char *blobdir, DBT *blobData)
{
    const char *name;

    if (blobdir == NULL) {
        PR_SetError(SEC_ERROR_BAD_DATABASE, 0);
        return NULL;
    }
    if (!dbs_IsBlob(blobData)) {
        PR_SetError(SEC_ERROR_BAD_DATABASE, 0);
        return NULL;
    }
    name = dbs_getBlobFileName(blobData);
    if (!name || *name == 0) {
        PR_SetError(SEC_ERROR_BAD_DATABASE, 0);
        return NULL;
    }
    return PR_smprintf("%s" PATH_SEPARATOR "%s", blobdir, name);
}

/*
 * Delete a blob file pointed to by the blob record.
 */
static void
dbs_removeBlob(DBS *dbsp, DBT *blobData)
{
    char *file;

    file = dbs_getBlobFilePath(dbsp->blobdir, blobData);
    if (!file) {
        return;
    }
    PR_Delete(file);
    PR_smprintf_free(file);
}

/*
 * Directory modes are slightly different, the 'x' bit needs to be on to
 * access them. Copy all the read bits to 'x' bits
 */
static int
dbs_DirMode(int mode)
{
    int x_bits = (mode >> 2) & 0111;
    return mode | x_bits;
}

/*
 * write a data blob to it's file. blobdData is the blob record that will be
 * stored in the database. data is the actual data to go out on disk.
 */
static int
dbs_writeBlob(DBS *dbsp, int mode, DBT *blobData, const DBT *data)
{
    char *file = NULL;
    PRFileDesc *filed;
    PRStatus status;
    int len;
    int error = 0;

    file = dbs_getBlobFilePath(dbsp->blobdir, blobData);
    if (!file) {
        goto loser;
    }
    if (PR_Access(dbsp->blobdir, PR_ACCESS_EXISTS) != PR_SUCCESS) {
        status = PR_MkDir(dbsp->blobdir, dbs_DirMode(mode));
        if (status != PR_SUCCESS) {
            goto loser;
        }
    }
    filed = PR_OpenFile(file, PR_CREATE_FILE | PR_TRUNCATE | PR_WRONLY, mode);
    if (filed == NULL) {
        error = PR_GetError();
        goto loser;
    }
    len = PR_Write(filed, data->data, data->size);
    error = PR_GetError();
    PR_Close(filed);
    if (len < (int)data->size) {
        goto loser;
    }
    PR_smprintf_free(file);
    return 0;

loser:
    if (file) {
        PR_Delete(file);
        PR_smprintf_free(file);
    }
    /* don't let close or delete reset the error */
    PR_SetError(error, 0);
    return -1;
}

/*
 * platforms that cannot map the file need to read it into a temp buffer.
 */
static unsigned char *
dbs_EmulateMap(PRFileDesc *filed, int len)
{
    unsigned char *addr;
    PRInt32 dataRead;

    addr = PORT_Alloc(len);
    if (addr == NULL) {
        return NULL;
    }

    dataRead = PR_Read(filed, addr, len);
    if (dataRead != len) {
        PORT_Free(addr);
        if (dataRead > 0) {
            /* PR_Read didn't set an error, we need to */
            PR_SetError(SEC_ERROR_BAD_DATABASE, 0);
        }
        return NULL;
    }

    return addr;
}

/*
 * pull a database record off the disk
 * data points to the blob record on input and the real record (if we could
 * read it) on output. if there is an error data is not modified.
 */
static int
dbs_readBlob(DBS *dbsp, DBT *data)
{
    char *file = NULL;
    PRFileDesc *filed = NULL;
    unsigned char *addr = NULL;
    int error;
    int len = -1;

    file = dbs_getBlobFilePath(dbsp->blobdir, data);
    if (!file) {
        goto loser;
    }
    filed = PR_OpenFile(file, PR_RDONLY, 0);
    PR_smprintf_free(file);
    file = NULL;
    if (filed == NULL) {
        goto loser;
    }

    len = dbs_getBlobSize(data);
    /* Bug 1323150
     * PR_MemMap fails on Windows for larger certificates.
     * https://msdn.microsoft.com/en-us/library/windows/desktop/aa366761(v=vs.85).aspx
     * Let's always use the emulated map, i.e. read the file.
     */
    addr = dbs_EmulateMap(filed, len);
    if (addr == NULL) {
        goto loser;
    }
    PR_Close(filed);

    data->data = addr;
    data->size = len;
    return 0;

loser:
    /* preserve the error code */
    error = PR_GetError();
    if (filed) {
        PR_Close(filed);
    }
    PR_SetError(error, 0);
    return -1;
}

/*
 * actual DBM shims
 */
static int
dbs_get(const DB *dbs, const DBT *key, DBT *data, unsigned int flags)
{
    int ret;
    DBS *dbsp = (DBS *)dbs;
    DB *db = (DB *)dbs->internal;

    ret = (*db->get)(db, key, data, flags);
    if ((ret == 0) && dbs_IsBlob(data)) {
        ret = dbs_readBlob(dbsp, data);
    }

    return (ret);
}

static int
dbs_put(const DB *dbs, DBT *key, const DBT *data, unsigned int flags)
{
    DBT blob;
    int ret = 0;
    DBS *dbsp = (DBS *)dbs;
    DB *db = (DB *)dbs->internal;

    /* If the db is readonly, just pass the data down to rdb and let it fail */
    if (!dbsp->readOnly) {
        DBT oldData;
        int ret1;

        /* make sure the current record is deleted if it's a blob */
        ret1 = (*db->get)(db, key, &oldData, 0);
        if ((ret1 == 0) && flags == R_NOOVERWRITE) {
            /* let DBM return the error to maintain consistancy */
            return (*db->put)(db, key, data, flags);
        }
        if ((ret1 == 0) && dbs_IsBlob(&oldData)) {
            dbs_removeBlob(dbsp, &oldData);
        }

        if (data->size > DBS_MAX_ENTRY_SIZE) {
            dbs_mkBlob(dbsp, key, data, &blob);
            ret = dbs_writeBlob(dbsp, dbsp->mode, &blob, data);
            data = &blob;
        }
    }

    if (ret == 0) {
        ret = (*db->put)(db, key, data, flags);
    }
    return (ret);
}

static int
dbs_sync(const DB *dbs, unsigned int flags)
{
    DB *db = (DB *)dbs->internal;
    return (*db->sync)(db, flags);
}

static int
dbs_del(const DB *dbs, const DBT *key, unsigned int flags)
{
    int ret;
    DBS *dbsp = (DBS *)dbs;
    DB *db = (DB *)dbs->internal;

    if (!dbsp->readOnly) {
        DBT oldData;
        ret = (*db->get)(db, key, &oldData, 0);
        if ((ret == 0) && dbs_IsBlob(&oldData)) {
            dbs_removeBlob(dbsp, &oldData);
        }
    }

    return (*db->del)(db, key, flags);
}

static int
dbs_seq(const DB *dbs, DBT *key, DBT *data, unsigned int flags)
{
    int ret;
    DBS *dbsp = (DBS *)dbs;
    DB *db = (DB *)dbs->internal;

    ret = (*db->seq)(db, key, data, flags);
    if ((ret == 0) && dbs_IsBlob(data)) {
        /* don't return a blob read as an error so traversals keep going */
        (void)dbs_readBlob(dbsp, data);
    }

    return (ret);
}

static int
dbs_close(DB *dbs)
{
    DBS *dbsp = (DBS *)dbs;
    DB *db = (DB *)dbs->internal;
    int ret;

    ret = (*db->close)(db);
    PORT_Free(dbsp->blobdir);
    PORT_Free(dbsp);
    return ret;
}

static int
dbs_fd(const DB *dbs)
{
    DB *db = (DB *)dbs->internal;

    return (*db->fd)(db);
}

/*
 * the naming convention we use is
 * change the .xxx into .dir. (for nss it's always .db);
 * if no .extension exists or is equal to .dir, add a .dir
 * the returned data must be freed.
 */
#define DIRSUFFIX ".dir"
static char *
dbs_mkBlobDirName(const char *dbname)
{
    int dbname_len = PORT_Strlen(dbname);
    int dbname_end = dbname_len;
    const char *cp;
    char *blobDir = NULL;

    /* scan back from the end looking for either a directory separator, a '.',
     * or the end of the string. NOTE: Windows should check for both separators
     * here. For now this is safe because we know NSS always uses a '.'
     */
    for (cp = &dbname[dbname_len];
         (cp > dbname) && (*cp != '.') && (*cp != *PATH_SEPARATOR);
         cp--)
        /* Empty */;
    if (*cp == '.') {
        dbname_end = cp - dbname;
        if (PORT_Strcmp(cp, DIRSUFFIX) == 0) {
            dbname_end = dbname_len;
        }
    }
    blobDir = PORT_ZAlloc(dbname_end + sizeof(DIRSUFFIX));
    if (blobDir == NULL) {
        return NULL;
    }
    PORT_Memcpy(blobDir, dbname, dbname_end);
    PORT_Memcpy(&blobDir[dbname_end], DIRSUFFIX, sizeof(DIRSUFFIX));
    return blobDir;
}

#define DBM_DEFAULT 0
static const HASHINFO dbs_hashInfo = {
    DBS_BLOCK_SIZE, /* bucket size, must be greater than = to
                     * or maximum entry size (+ header)
                     * we allow before blobing */
    DBM_DEFAULT,    /* Fill Factor */
    DBM_DEFAULT,    /* number of elements */
    DBS_CACHE_SIZE, /* cache size */
    DBM_DEFAULT,    /* hash function */
    DBM_DEFAULT,    /* byte order */
};

/*
 * the open function. NOTE: this is the only exposed function in this file.
 * everything else is called through the function table pointer.
 */
DB *
dbsopen(const char *dbname, int flags, int mode, DBTYPE type,
        const void *userData)
{
    DB *db = NULL, *dbs = NULL;
    DBS *dbsp = NULL;

    /* NOTE: we are overriding userData with dbs_hashInfo. since all known
     * callers pass 0, this is ok, otherwise we should merge the two */

    dbsp = (DBS *)PORT_ZAlloc(sizeof(DBS));
    if (!dbsp) {
        return NULL;
    }
    dbs = &dbsp->db;

    dbsp->blobdir = dbs_mkBlobDirName(dbname);
    if (dbsp->blobdir == NULL) {
        goto loser;
    }
    dbsp->mode = mode;
    dbsp->readOnly = (PRBool)(flags == NO_RDONLY);

    /* the real dbm call */
    db = dbopen(dbname, flags, mode, type, &dbs_hashInfo);
    if (db == NULL) {
        goto loser;
    }
    dbs->internal = (void *)db;
    dbs->type = type;
    dbs->close = dbs_close;
    dbs->get = dbs_get;
    dbs->del = dbs_del;
    dbs->put = dbs_put;
    dbs->seq = dbs_seq;
    dbs->sync = dbs_sync;
    dbs->fd = dbs_fd;

    return dbs;
loser:
    if (db) {
        (*db->close)(db);
    }
    if (dbsp->blobdir) {
        PORT_Free(dbsp->blobdir);
    }
    PORT_Free(dbsp);
    return NULL;
}
