storage/proxy/rpmb.c

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <errno.h>
#include <fcntl.h>
#include <scsi/scsi.h>
#include <scsi/scsi_proto.h>
#include <scsi/sg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#include <linux/major.h>
#include <linux/mmc/ioctl.h>

#include <hardware_legacy/power.h>

#include "ipc.h"
#include "log.h"
#include "rpmb.h"
#include "storage.h"

#define MMC_READ_MULTIPLE_BLOCK 18
#define MMC_WRITE_MULTIPLE_BLOCK 25
#define MMC_RELIABLE_WRITE_FLAG (1 << 31)

#define MMC_RSP_PRESENT (1 << 0)
#define MMC_RSP_CRC (1 << 2)
#define MMC_RSP_OPCODE (1 << 4)
#define MMC_CMD_ADTC (1 << 5)
#define MMC_RSP_SPI_S1 (1 << 7)
#define MMC_RSP_R1 (MMC_RSP_PRESENT | MMC_RSP_CRC | MMC_RSP_OPCODE)
#define MMC_RSP_SPI_R1 (MMC_RSP_SPI_S1)

#define MMC_WRITE_FLAG_R 0
#define MMC_WRITE_FLAG_W 1
#define MMC_WRITE_FLAG_RELW (MMC_WRITE_FLAG_W | MMC_RELIABLE_WRITE_FLAG)

#define MMC_BLOCK_SIZE 512

/*
 * Number of retry attempts when an RPMB authenticated write triggers a UNIT
 * ATTENTION
 */
#define UFS_RPMB_WRITE_RETRY_COUNT 1
/*
 * Number of retry attempts when an RPMB read operation triggers a UNIT
 * ATTENTION
 */
#define UFS_RPMB_READ_RETRY_COUNT 3

/*
 * There should be no timeout for security protocol ioctl call, so we choose a
 * large number for timeout.
 * 20000 millisecs == 20 seconds
 */
#define TIMEOUT 20000

/*
 * The sg device driver that supports new interface has a major version number of "3".
 * SG_GET_VERSION_NUM ioctl() will yield a number greater than or 30000.
 */
#define RPMB_MIN_SG_VERSION_NUM 30000

/*
 * CDB format of SECURITY PROTOCOL IN/OUT commands
 * (JEDEC Standard No. 220D, Page 264)
 */
struct sec_proto_cdb {
    /*
     * OPERATION CODE = A2h for SECURITY PROTOCOL IN command,
     * OPERATION CODE = B5h for SECURITY PROTOCOL OUT command.
     */
    uint8_t opcode;
    /* SECURITY PROTOCOL = ECh (JEDEC Universal Flash Storage) */
    uint8_t sec_proto;
    /*
     * The SECURITY PROTOCOL SPECIFIC field specifies the RPMB Protocol ID.
     * CDB Byte 2 = 00h and CDB Byte 3 = 01h for RPMB Region 0.
     */
    uint8_t cdb_byte_2;
    uint8_t cdb_byte_3;
    /*
     * Byte 4 and 5 are reserved.
     */
    uint8_t cdb_byte_4;
    uint8_t cdb_byte_5;
    /* ALLOCATION/TRANSFER LENGTH in big-endian */
    uint32_t length;
    /* Byte 9 is reserved. */
    uint8_t cdb_byte_10;
    /* CONTROL = 00h. */
    uint8_t ctrl;
} __packed;

static int rpmb_fd = -1;
static uint8_t read_buf[4096];
static enum dev_type dev_type = UNKNOWN_RPMB;

static const char* UFS_WAKE_LOCK_NAME = "ufs_seq_wakelock";

/**
 * log_buf - Log a byte buffer to the android log.
 * @priority: One of ANDROID_LOG_* priority levels from android_LogPriority in
 *            android/log.h
 * @prefix:   A null-terminated string that identifies this buffer. Must be less
 *            than 128 bytes.
 * @buf:      Buffer to dump.
 * @size:     Length of @buf in bytes.
 */
#define LOG_BUF_SIZE 256
static int log_buf(int priority, const char* prefix, const uint8_t* buf, size_t size) {
    int rc;
    size_t i;
    char line[LOG_BUF_SIZE] = {0};
    char* cur = line;

    rc = snprintf(line, LOG_BUF_SIZE, "%s @%p [%zu]", prefix, buf, size);
    if (rc < 0 || rc >= LOG_BUF_SIZE) {
        goto err;
    }
    cur += rc;
    for (i = 0; i < size; i++) {
        if (i % 32 == 0) {
            /*
             * Flush the line out to the log after we have printed 32 bytes
             * (also flushes the header line on the first iteration and sets up
             * for printing the buffer itself)
             */
            LOG_PRI(priority, LOG_TAG, "%s", line);
            memset(line, 0, LOG_BUF_SIZE);
            cur = line;
            /* Shift output over by the length of the prefix */
            rc = snprintf(line, LOG_BUF_SIZE, "%*s", (int)strlen(prefix), "");
            if (rc < 0 || rc >= LOG_BUF_SIZE) {
                goto err;
            }
            cur += rc;
        }
        rc = snprintf(cur, LOG_BUF_SIZE - (cur - line), "%02x ", buf[i]);
        if (rc < 0 || rc >= LOG_BUF_SIZE - (cur - line)) {
            goto err;
        }
        cur += rc;
    }
    LOG_PRI(priority, LOG_TAG, "%s", line);

    return 0;

err:
    if (rc < 0) {
        return rc;
    } else {
        ALOGE("log_buf prefix was too long");
        return -1;
    }
}

static void set_sg_io_hdr(sg_io_hdr_t* io_hdrp, int dxfer_direction, unsigned char cmd_len,
                          unsigned char mx_sb_len, unsigned int dxfer_len, void* dxferp,
                          unsigned char* cmdp, void* sbp) {
    memset(io_hdrp, 0, sizeof(sg_io_hdr_t));
    io_hdrp->interface_id = 'S';
    io_hdrp->dxfer_direction = dxfer_direction;
    io_hdrp->cmd_len = cmd_len;
    io_hdrp->mx_sb_len = mx_sb_len;
    io_hdrp->dxfer_len = dxfer_len;
    io_hdrp->dxferp = dxferp;
    io_hdrp->cmdp = cmdp;
    io_hdrp->sbp = sbp;
    io_hdrp->timeout = TIMEOUT;
}

/**
 * enum scsi_result - Results of checking the SCSI status and sense buffer
 *
 * @SCSI_RES_OK:    SCSI status and sense are good
 * @SCSI_RES_ERR:   SCSI status or sense contain an unhandled error
 * @SCSI_RES_RETRY: SCSI sense buffer contains a status that indicates that the
 *                  command should be retried
 */
enum scsi_result {
    SCSI_RES_OK = 0,
    SCSI_RES_ERR,
    SCSI_RES_RETRY,
};

static enum scsi_result check_scsi_sense(const uint8_t* sense_buf, size_t len) {
    uint8_t response_code = 0;
    uint8_t sense_key = 0;
    uint8_t additional_sense_code = 0;
    uint8_t additional_sense_code_qualifier = 0;
    uint8_t additional_length = 0;

    if (!sense_buf || len == 0) {
        ALOGE("Invalid SCSI sense buffer, length: %zu\n", len);
        return SCSI_RES_ERR;
    }

    response_code = 0x7f & sense_buf[0];

    if (response_code < 0x70 || response_code > 0x73) {
        ALOGE("Invalid SCSI sense response code: %hhu\n", response_code);
        return SCSI_RES_ERR;
    }

    if (response_code >= 0x72) {
        /* descriptor format, SPC-6 4.4.2 */
        if (len > 1) {
            sense_key = 0xf & sense_buf[1];
        }
        if (len > 2) {
            additional_sense_code = sense_buf[2];
        }
        if (len > 3) {
            additional_sense_code_qualifier = sense_buf[3];
        }
        if (len > 7) {
            additional_length = sense_buf[7];
        }
    } else {
        /* fixed format, SPC-6 4.4.3 */
        if (len > 2) {
            sense_key = 0xf & sense_buf[2];
        }
        if (len > 7) {
            additional_length = sense_buf[7];
        }
        if (len > 12) {
            additional_sense_code = sense_buf[12];
        }
        if (len > 13) {
            additional_sense_code_qualifier = sense_buf[13];
        }
    }

    switch (sense_key) {
        case NO_SENSE:
        case 0x0f: /* COMPLETED, not present in kernel headers */
            ALOGD("SCSI success with sense data: key=%hhu, asc=%hhu, ascq=%hhu\n", sense_key,
                  additional_sense_code, additional_sense_code_qualifier);
            return SCSI_RES_OK;
        case UNIT_ATTENTION:
            ALOGD("UNIT ATTENTION with sense data: key=%hhu, asc=%hhu, ascq=%hhu\n", sense_key,
                  additional_sense_code, additional_sense_code_qualifier);
            if (additional_sense_code == 0x29) {
                /* POWER ON or RESET condition */
                return SCSI_RES_RETRY;
            }

            /* treat this UNIT ATTENTION as an error if we don't recognize it */
            break;
    }

    ALOGE("Unexpected SCSI sense data: key=%hhu, asc=%hhu, ascq=%hhu\n", sense_key,
          additional_sense_code, additional_sense_code_qualifier);
    log_buf(ANDROID_LOG_ERROR, "sense buffer: ", sense_buf, len);
    return SCSI_RES_ERR;
}

static enum scsi_result check_sg_io_hdr(const sg_io_hdr_t* io_hdrp) {
    if (io_hdrp->status == 0 && io_hdrp->host_status == 0 && io_hdrp->driver_status == 0) {
        return SCSI_RES_OK;
    }

    if (io_hdrp->status & 0x01) {
        ALOGE("SG_IO received unknown status, LSB is set: %hhu", io_hdrp->status);
    }

    if (io_hdrp->masked_status != GOOD && io_hdrp->sb_len_wr > 0) {
        enum scsi_result scsi_res = check_scsi_sense(io_hdrp->sbp, io_hdrp->sb_len_wr);
        if (scsi_res == SCSI_RES_RETRY) {
            return SCSI_RES_RETRY;
        } else if (scsi_res != SCSI_RES_OK) {
            ALOGE("Unexpected SCSI sense. masked_status: %hhu, host_status: %hu, driver_status: "
                  "%hu\n",
                  io_hdrp->masked_status, io_hdrp->host_status, io_hdrp->driver_status);
            return scsi_res;
        }
    }

    switch (io_hdrp->masked_status) {
        case GOOD:
            break;
        case CHECK_CONDITION:
            /* handled by check_sg_sense above */
            break;
        default:
            ALOGE("SG_IO failed with masked_status: %hhu, host_status: %hu, driver_status: %hu\n",
                  io_hdrp->masked_status, io_hdrp->host_status, io_hdrp->driver_status);
            return SCSI_RES_ERR;
    }

    if (io_hdrp->host_status != 0) {
        ALOGE("SG_IO failed with host_status: %hu, driver_status: %hu\n", io_hdrp->host_status,
              io_hdrp->driver_status);
    }

    if (io_hdrp->resid != 0) {
        ALOGE("SG_IO resid was non-zero: %d\n", io_hdrp->resid);
    }
    return SCSI_RES_ERR;
}

static int send_mmc_rpmb_req(int mmc_fd, const struct storage_rpmb_send_req* req,
                             struct watcher* watcher) {
    union {
        struct mmc_ioc_multi_cmd multi;
        uint8_t raw[sizeof(struct mmc_ioc_multi_cmd) + sizeof(struct mmc_ioc_cmd) * 3];
    } mmc = {};
    struct mmc_ioc_cmd* cmd = mmc.multi.cmds;
    int rc;

    const uint8_t* write_buf = req->payload;
    if (req->reliable_write_size) {
        cmd->write_flag = MMC_WRITE_FLAG_RELW;
        cmd->opcode = MMC_WRITE_MULTIPLE_BLOCK;
        cmd->flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
        cmd->blksz = MMC_BLOCK_SIZE;
        cmd->blocks = req->reliable_write_size / MMC_BLOCK_SIZE;
        mmc_ioc_cmd_set_data((*cmd), write_buf);
#ifdef RPMB_DEBUG
        ALOGI("opcode: 0x%x, write_flag: 0x%x\n", cmd->opcode, cmd->write_flag);
        log_buf(ANDROID_LOG_INFO, "request: ", write_buf, req->reliable_write_size);
#endif
        write_buf += req->reliable_write_size;
        mmc.multi.num_of_cmds++;
        cmd++;
    }

    if (req->write_size) {
        cmd->write_flag = MMC_WRITE_FLAG_W;
        cmd->opcode = MMC_WRITE_MULTIPLE_BLOCK;
        cmd->flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
        cmd->blksz = MMC_BLOCK_SIZE;
        cmd->blocks = req->write_size / MMC_BLOCK_SIZE;
        mmc_ioc_cmd_set_data((*cmd), write_buf);
#ifdef RPMB_DEBUG
        ALOGI("opcode: 0x%x, write_flag: 0x%x\n", cmd->opcode, cmd->write_flag);
        log_buf(ANDROID_LOG_INFO, "request: ", write_buf, req->write_size);
#endif
        write_buf += req->write_size;
        mmc.multi.num_of_cmds++;
        cmd++;
    }

    if (req->read_size) {
        cmd->write_flag = MMC_WRITE_FLAG_R;
        cmd->opcode = MMC_READ_MULTIPLE_BLOCK;
        cmd->flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC, cmd->blksz = MMC_BLOCK_SIZE;
        cmd->blocks = req->read_size / MMC_BLOCK_SIZE;
        mmc_ioc_cmd_set_data((*cmd), read_buf);
#ifdef RPMB_DEBUG
        ALOGI("opcode: 0x%x, write_flag: 0x%x\n", cmd->opcode, cmd->write_flag);
#endif
        mmc.multi.num_of_cmds++;
        cmd++;
    }

    watch_progress(watcher, "rpmb mmc ioctl");
    rc = ioctl(mmc_fd, MMC_IOC_MULTI_CMD, &mmc.multi);
    watch_progress(watcher, "rpmb mmc ioctl done");
    if (rc < 0) {
        ALOGE("%s: mmc ioctl failed: %d, %s\n", __func__, rc, strerror(errno));
    }
    return rc;
}

static int send_ufs_rpmb_req(int sg_fd, const struct storage_rpmb_send_req* req,
                             struct watcher* watcher) {
    int rc;
    int wl_rc;
    const uint8_t* write_buf = req->payload;
    /*
     * Meaning of member values are stated on the definition of struct sec_proto_cdb.
     */
    struct sec_proto_cdb in_cdb = {0xA2, 0xEC, 0x00, 0x01, 0x00, 0x00, 0, 0x00, 0x00};
    struct sec_proto_cdb out_cdb = {0xB5, 0xEC, 0x00, 0x01, 0x00, 0x00, 0, 0x00, 0x00};
    unsigned char sense_buffer[32];

    bool is_request_write = req->reliable_write_size > 0;

    /*
     * Internally this call connects to the suspend service, which will cause
     * this service to start if not already running. If the binder thread pool
     * has not been started at this point, this call will block and poll for the
     * service every 1s. We need to make sure the thread pool is started to
     * receive an async notification that the service is started to avoid
     * blocking (see main).
     */
    wl_rc = acquire_wake_lock(PARTIAL_WAKE_LOCK, UFS_WAKE_LOCK_NAME);
    if (wl_rc < 0) {
        ALOGE("%s: failed to acquire wakelock: %d, %s\n", __func__, wl_rc, strerror(errno));
        return wl_rc;
    }

    if (req->reliable_write_size) {
        /* Prepare SECURITY PROTOCOL OUT command. */
        sg_io_hdr_t io_hdr;
        int retry_count = UFS_RPMB_WRITE_RETRY_COUNT;
        do {
            out_cdb.length = __builtin_bswap32(req->reliable_write_size);
            set_sg_io_hdr(&io_hdr, SG_DXFER_TO_DEV, sizeof(out_cdb), sizeof(sense_buffer),
                          req->reliable_write_size, (void*)write_buf, (unsigned char*)&out_cdb,
                          sense_buffer);
            watch_progress(watcher, "rpmb ufs reliable write");
            rc = ioctl(sg_fd, SG_IO, &io_hdr);
            watch_progress(watcher, "rpmb ufs reliable write done");
            if (rc < 0) {
                ALOGE("%s: ufs ioctl failed: %d, %s\n", __func__, rc, strerror(errno));
                goto err_op;
            }
        } while (check_sg_io_hdr(&io_hdr) == SCSI_RES_RETRY && retry_count-- > 0);
        write_buf += req->reliable_write_size;
    }

    if (req->write_size) {
        /* Prepare SECURITY PROTOCOL OUT command. */
        sg_io_hdr_t io_hdr;
        /*
         * We don't retry write response request messages (is_request_write ==
         * true) because a unit attention condition between the write and
         * requesting a response means that the device was reset and we can't
         * get a response to our original write. We can only retry this SG_IO
         * call when it is the first call in our sequence.
         */
        int retry_count = is_request_write ? 0 : UFS_RPMB_READ_RETRY_COUNT;
        do {
            out_cdb.length = __builtin_bswap32(req->write_size);
            set_sg_io_hdr(&io_hdr, SG_DXFER_TO_DEV, sizeof(out_cdb), sizeof(sense_buffer),
                          req->write_size, (void*)write_buf, (unsigned char*)&out_cdb,
                          sense_buffer);
            watch_progress(watcher, "rpmb ufs write");
            rc = ioctl(sg_fd, SG_IO, &io_hdr);
            watch_progress(watcher, "rpmb ufs write done");
            if (rc < 0) {
                ALOGE("%s: ufs ioctl failed: %d, %s\n", __func__, rc, strerror(errno));
                goto err_op;
            }
        } while (check_sg_io_hdr(&io_hdr) == SCSI_RES_RETRY && retry_count-- > 0);
        write_buf += req->write_size;
    }

    if (req->read_size) {
        /* Prepare SECURITY PROTOCOL IN command. */
        in_cdb.length = __builtin_bswap32(req->read_size);
        sg_io_hdr_t io_hdr;
        set_sg_io_hdr(&io_hdr, SG_DXFER_FROM_DEV, sizeof(in_cdb), sizeof(sense_buffer),
                      req->read_size, read_buf, (unsigned char*)&in_cdb, sense_buffer);
        watch_progress(watcher, "rpmb ufs read");
        rc = ioctl(sg_fd, SG_IO, &io_hdr);
        watch_progress(watcher, "rpmb ufs read done");
        if (rc < 0) {
            ALOGE("%s: ufs ioctl failed: %d, %s\n", __func__, rc, strerror(errno));
        }
        check_sg_io_hdr(&io_hdr);
    }

err_op:
    wl_rc = release_wake_lock(UFS_WAKE_LOCK_NAME);
    if (wl_rc < 0) {
        ALOGE("%s: failed to release wakelock: %d, %s\n", __func__, wl_rc, strerror(errno));
    }

    return rc;
}

static int send_virt_rpmb_req(int rpmb_fd, void* read_buf, size_t read_size, const void* payload,
                              size_t payload_size) {
    int rc;
    uint16_t res_count = read_size / MMC_BLOCK_SIZE;
    uint16_t cmd_count = payload_size / MMC_BLOCK_SIZE;
    rc = write(rpmb_fd, &res_count, sizeof(res_count));
    if (rc < 0) {
        return rc;
    }
    rc = write(rpmb_fd, &cmd_count, sizeof(cmd_count));
    if (rc < 0) {
        return rc;
    }
    rc = write(rpmb_fd, payload, payload_size);
    if (rc < 0) {
        return rc;
    }
    rc = read(rpmb_fd, read_buf, read_size);
    return rc;
}

int rpmb_send(struct storage_msg* msg, const void* r, size_t req_len, struct watcher* watcher) {
    int rc;
    const struct storage_rpmb_send_req* req = r;

    if (req_len < sizeof(*req)) {
        ALOGW("malformed rpmb request: invalid length (%zu < %zu)\n", req_len, sizeof(*req));
        msg->result = STORAGE_ERR_NOT_VALID;
        goto err_response;
    }

    size_t expected_len = sizeof(*req) + req->reliable_write_size + req->write_size;
    if (req_len != expected_len) {
        ALOGW("malformed rpmb request: invalid length (%zu != %zu)\n", req_len, expected_len);
        msg->result = STORAGE_ERR_NOT_VALID;
        goto err_response;
    }

    if ((req->reliable_write_size % MMC_BLOCK_SIZE) != 0) {
        ALOGW("invalid reliable write size %u\n", req->reliable_write_size);
        msg->result = STORAGE_ERR_NOT_VALID;
        goto err_response;
    }

    if ((req->write_size % MMC_BLOCK_SIZE) != 0) {
        ALOGW("invalid write size %u\n", req->write_size);
        msg->result = STORAGE_ERR_NOT_VALID;
        goto err_response;
    }

    if (req->read_size % MMC_BLOCK_SIZE != 0 || req->read_size > sizeof(read_buf)) {
        ALOGE("%s: invalid read size %u\n", __func__, req->read_size);
        msg->result = STORAGE_ERR_NOT_VALID;
        goto err_response;
    }

    if (dev_type == MMC_RPMB) {
        rc = send_mmc_rpmb_req(rpmb_fd, req, watcher);
        if (rc < 0) {
            msg->result = STORAGE_ERR_GENERIC;
            goto err_response;
        }
    } else if (dev_type == UFS_RPMB) {
        rc = send_ufs_rpmb_req(rpmb_fd, req, watcher);
        if (rc < 0) {
            ALOGE("send_ufs_rpmb_req failed: %d, %s\n", rc, strerror(errno));
            msg->result = STORAGE_ERR_GENERIC;
            goto err_response;
        }
    } else if ((dev_type == VIRT_RPMB) || (dev_type == SOCK_RPMB)) {
        size_t payload_size = req->reliable_write_size + req->write_size;
        rc = send_virt_rpmb_req(rpmb_fd, read_buf, req->read_size, req->payload, payload_size);
        if (rc < 0) {
            ALOGE("send_virt_rpmb_req failed: %d, %s\n", rc, strerror(errno));
            msg->result = STORAGE_ERR_GENERIC;
            goto err_response;
        }
        if (rc != req->read_size) {
            ALOGE("send_virt_rpmb_req got incomplete response: "
                  "(size %d, expected %d)\n",
                  rc, req->read_size);
            msg->result = STORAGE_ERR_GENERIC;
            goto err_response;
        }
    } else {
        ALOGE("Unsupported dev_type\n");
        msg->result = STORAGE_ERR_GENERIC;
        goto err_response;
    }
#ifdef RPMB_DEBUG
    if (req->read_size) log_buf(ANDROID_LOG_INFO, "response: ", read_buf, req->read_size);
#endif

    if (msg->flags & STORAGE_MSG_FLAG_POST_COMMIT) {
        /*
         * Nothing todo for post msg commit request as MMC_IOC_MULTI_CMD
         * is fully synchronous in this implementation.
         */
    }

    msg->result = STORAGE_NO_ERROR;
    return ipc_respond(msg, read_buf, req->read_size);

err_response:
    return ipc_respond(msg, NULL, 0);
}

int rpmb_open(const char* rpmb_devname, enum dev_type open_dev_type) {
    int rc, sg_version_num;
    dev_type = open_dev_type;

    if (dev_type != SOCK_RPMB) {
        rc = open(rpmb_devname, O_RDWR, 0);
        if (rc < 0) {
            ALOGE("unable (%d) to open rpmb device '%s': %s\n", errno, rpmb_devname, strerror(errno));
            return rc;
        }
        rpmb_fd = rc;

        /* For UFS, it is prudent to check we have a sg device by calling an ioctl */
        if (dev_type == UFS_RPMB) {
            if ((ioctl(rpmb_fd, SG_GET_VERSION_NUM, &sg_version_num) < 0) ||
                (sg_version_num < RPMB_MIN_SG_VERSION_NUM)) {
                ALOGE("%s is not a sg device, or old sg driver\n", rpmb_devname);
                return -1;
            }
        }
    } else {
        struct sockaddr_un unaddr;
        struct sockaddr *addr = (struct sockaddr *)&unaddr;
        rc = socket(AF_UNIX, SOCK_STREAM, 0);
        if (rc < 0) {
            ALOGE("unable (%d) to create socket: %s\n", errno, strerror(errno));
            return rc;
        }
        rpmb_fd = rc;

        memset(&unaddr, 0, sizeof(unaddr));
        unaddr.sun_family = AF_UNIX;
        // TODO if it overflowed, bail rather than connecting?
        strncpy(unaddr.sun_path, rpmb_devname, sizeof(unaddr.sun_path)-1);
        rc = connect(rpmb_fd, addr, sizeof(unaddr));
        if (rc < 0) {
            ALOGE("unable (%d) to connect to rpmb socket '%s': %s\n", errno, rpmb_devname, strerror(errno));
            return rc;
        }
    }

    return 0;
}

void rpmb_close(void) {
    close(rpmb_fd);
    rpmb_fd = -1;
}