src/lib-ssl-iostream/iostream-openssl.c

	iostream-openssl.c revision ed41ec8aa0efaa50954fd16cb44c86c8350dadcc
/* Copyright (c) 2009 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "istream.h"
#include "ostream.h"
#include "iostream-openssl.h"

#include <openssl/err.h>
#include <openssl/x509v3.h>

static void ssl_iostream_free(struct ssl_iostream *ssl_io);

static void ssl_info_callback(const SSL *ssl, int where, int ret)
{
    struct ssl_iostream *ssl_io;

    ssl_io = SSL_get_ex_data(ssl, dovecot_ssl_extdata_index);
    if ((where & SSL_CB_ALERT) != 0) {
        i_warning("%s: SSL alert: where=0x%x, ret=%d: %s %s",
              ssl_io->source, where, ret,
              SSL_alert_type_string_long(ret),
              SSL_alert_desc_string_long(ret));
    } else if (ret == 0) {
        i_warning("%s: SSL failed: where=0x%x: %s",
              ssl_io->source, where, SSL_state_string_long(ssl));
    } else {
        i_warning("%s: SSL: where=0x%x, ret=%d: %s",
              ssl_io->source, where, ret,
              SSL_state_string_long(ssl));
    }
}

static int
ssl_iostream_use_certificate(struct ssl_iostream *ssl_io, const char *cert)
{
    BIO *in;
    X509 *x;
    int ret = 0;

    in = BIO_new_mem_buf(t_strdup_noconst(cert), strlen(cert));
    if (in == NULL) {
        i_error("BIO_new_mem_buf() failed: %s", ssl_iostream_error());
        return -1;
    }

    x = PEM_read_bio_X509(in, NULL, NULL, NULL);
    if (x != NULL) {
        ret = SSL_use_certificate(ssl_io->ssl, x);
        if (ERR_peek_error() != 0)
            ret = 0;
        X509_free(x);
    }
    BIO_free(in);

    if (ret == 0) {
        i_error("%s: Can't load ssl_cert: %s", ssl_io->source,
            ssl_iostream_get_use_certificate_error(cert));
        return -1;
    }
    return 0;
}

static int
ssl_iostream_use_key(struct ssl_iostream *ssl_io,
             const struct ssl_iostream_settings *set)
{
    EVP_PKEY *pkey;
    int ret = 0;

    if (ssl_iostream_load_key(set, ssl_io->source, &pkey) < 0)
        return -1;
    if (SSL_use_PrivateKey(ssl_io->ssl, pkey) != 1) {
        i_error("%s: Can't load SSL private key: %s",
            ssl_io->source, ssl_iostream_key_load_error());
        ret = -1;
    }
    EVP_PKEY_free(pkey);
    return ret;
}

static int
ssl_iostream_verify_client_cert(int preverify_ok, X509_STORE_CTX *ctx)
{
    int ssl_extidx = SSL_get_ex_data_X509_STORE_CTX_idx();
    SSL *ssl;
    struct ssl_iostream *ssl_io;

    ssl = X509_STORE_CTX_get_ex_data(ctx, ssl_extidx);
    ssl_io = SSL_get_ex_data(ssl, dovecot_ssl_extdata_index);
    ssl_io->cert_received = TRUE;

    if (ssl_io->verbose ||
        (ssl_io->verbose_invalid_cert && !preverify_ok)) {
        char buf[1024];
        X509_NAME *subject;

        subject = X509_get_subject_name(ctx->current_cert);
        if (subject == NULL ||
            X509_NAME_oneline(subject, buf, sizeof(buf)) == NULL)
            buf[0] = '\0';
        else
            buf[sizeof(buf)-1] = '\0'; /* just in case.. */
        if (!preverify_ok) {
            i_info("Invalid certificate: %s: %s",
                   X509_verify_cert_error_string(ctx->error), buf);
        } else {
            i_info("Valid certificate: %s", buf);
        }
    }
    if (!preverify_ok) {
        ssl_io->cert_broken = TRUE;
        if (ssl_io->require_valid_cert)
            return 0;
    }
    return 1;
}

static int
ssl_iostream_set(struct ssl_iostream *ssl_io,
         const struct ssl_iostream_settings *set)
{
    const struct ssl_iostream_settings *ctx_set = ssl_io->ctx->set;
    int verify_flags;

    if (set->verbose)
        SSL_set_info_callback(ssl_io->ssl, ssl_info_callback);

    if (set->cipher_list != NULL &&
        strcmp(ctx_set->cipher_list, set->cipher_list) != 0) {
        if (!SSL_set_cipher_list(ssl_io->ssl, set->cipher_list)) {
            i_error("%s: Can't set cipher list to '%s': %s",
                ssl_io->source, set->cipher_list,
                ssl_iostream_error());
        }
        return -1;

    }
    if (set->cert != NULL && strcmp(ctx_set->cert, set->cert) != 0) {
        if (ssl_iostream_use_certificate(ssl_io, set->cert) < 0)
            return -1;
    }
    if (set->key != NULL && strcmp(ctx_set->key, set->key) != 0) {
        if (ssl_iostream_use_key(ssl_io, set) < 0)
            return -1;
    }
    if (set->verify_remote_cert) {
        if (ssl_io->ctx->client_ctx)
            verify_flags = SSL_VERIFY_NONE;
        else
            verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE;
        SSL_set_verify(ssl_io->ssl, verify_flags,
                   ssl_iostream_verify_client_cert);
    }

    if (set->cert_username_field != NULL) {
        ssl_io->username_nid = OBJ_txt2nid(set->cert_username_field);
        if (ssl_io->username_nid == NID_undef) {
            i_error("%s: Invalid cert_username_field: %s",
                ssl_io->source, set->cert_username_field);
        }
    } else {
        ssl_io->username_nid = ssl_io->ctx->username_nid;
    }

    ssl_io->verbose = set->verbose;
    ssl_io->verbose_invalid_cert = set->verbose_invalid_cert;
    ssl_io->require_valid_cert = set->require_valid_cert;
    return 0;
}

int io_stream_create_ssl(struct ssl_iostream_context *ctx, const char *source,
             const struct ssl_iostream_settings *set,
             struct istream **input, struct ostream **output,
             struct ssl_iostream **iostream_r)
{
    struct ssl_iostream *ssl_io;
    SSL *ssl;
    BIO *bio_int, *bio_ext;
    int ret;

    ssl = SSL_new(ctx->ssl_ctx);
    if (ssl == NULL) {
        i_error("SSL_new() failed: %s", ssl_iostream_error());
        return -1;
    }

    /* BIO pairs use default buffer sizes (17 kB in OpenSSL 0.9.8e).
       Each of the BIOs have one "write buffer". BIO_write() copies data
       to them, while BIO_read() reads from the other BIO's write buffer
       into the given buffer. The bio_int is used by OpenSSL and bio_ext
       is used by this library. */
    if (BIO_new_bio_pair(&bio_int, 0, &bio_ext, 0) != 1) {
        i_error("BIO_new_bio_pair() failed: %s", ssl_iostream_error());
        SSL_free(ssl);
        return -1;
    }

    ssl_io = i_new(struct ssl_iostream, 1);
    ssl_io->refcount = 1;
    ssl_io->ctx = ctx;
    ssl_io->ssl = ssl;
    ssl_io->bio_ext = bio_ext;
    ssl_io->plain_input = *input;
    ssl_io->plain_output = *output;
    ssl_io->source = i_strdup(source);
    /* bio_int will be freed by SSL_free() */
    SSL_set_bio(ssl_io->ssl, bio_int, bio_int);
        SSL_set_ex_data(ssl_io->ssl, dovecot_ssl_extdata_index, ssl_io);

    i_stream_ref(ssl_io->plain_input);
    o_stream_ref(ssl_io->plain_output);

    T_BEGIN {
        ret = ssl_iostream_set(ssl_io, set);
    } T_END;
    if (ret < 0) {
        ssl_iostream_free(ssl_io);
        return -1;
    }

    o_stream_uncork(ssl_io->plain_output);

    *input = i_stream_create_ssl(ssl_io);
    *output = o_stream_create_ssl(ssl_io);

    ssl_io->ssl_output = *output;
    *iostream_r = ssl_io;
    return 0;
}

static void ssl_iostream_free(struct ssl_iostream *ssl_io)
{
    i_stream_unref(&ssl_io->plain_input);
    o_stream_unref(&ssl_io->plain_output);
    BIO_free(ssl_io->bio_ext);
    SSL_free(ssl_io->ssl);
    i_free(ssl_io->last_error);
    i_free(ssl_io->source);
    i_free(ssl_io);
}

void ssl_iostream_unref(struct ssl_iostream **_ssl_io)
{
    struct ssl_iostream *ssl_io = *_ssl_io;

    *_ssl_io = NULL;

    i_assert(ssl_io->refcount > 0);
    if (--ssl_io->refcount >= 0)
        return;

    ssl_iostream_free(ssl_io);
}

static bool ssl_iostream_bio_output(struct ssl_iostream *ssl_io)
{
    size_t bytes, max_bytes;
    ssize_t sent;
    unsigned char buffer[IO_BLOCK_SIZE];
    bool bytes_sent = FALSE;
    int ret;

    o_stream_cork(ssl_io->plain_output);
    while ((bytes = BIO_ctrl_pending(ssl_io->bio_ext)) > 0) {
        /* bytes contains how many SSL encrypted bytes we should be
           sending out */
        max_bytes = o_stream_get_buffer_avail_size(ssl_io->plain_output);
        if (bytes > max_bytes) {
            if (max_bytes == 0) {
                /* wait until output buffer clears */
                o_stream_set_flush_pending(ssl_io->plain_output,
                               TRUE);
                break;
            }
            bytes = max_bytes;
        }
        if (bytes > sizeof(buffer))
            bytes = sizeof(buffer);

        /* BIO_read() is guaranteed to return all the bytes that
           BIO_ctrl_pending() returned */
        ret = BIO_read(ssl_io->bio_ext, buffer, bytes);
        i_assert(ret == (int)bytes);

        /* we limited number of read bytes to plain_output's
           available size. this send() is guaranteed to either
           fully succeed or completely fail due to some error. */
        sent = o_stream_send(ssl_io->plain_output, buffer, bytes);
        if (sent < 0) {
            i_assert(ssl_io->plain_output->stream_errno != 0);
            ssl_io->plain_stream_errno =
                ssl_io->plain_output->stream_errno;
            ssl_io->closed = TRUE;
            break;
        }
        i_assert(sent == (ssize_t)bytes);
        bytes_sent = TRUE;
    }
    o_stream_uncork(ssl_io->plain_output);
    return bytes_sent;
}

static bool ssl_iostream_bio_input(struct ssl_iostream *ssl_io)
{
    const unsigned char *data;
    size_t bytes, size;
    bool bytes_read = FALSE;
    int ret;

    while ((bytes = BIO_ctrl_get_write_guarantee(ssl_io->bio_ext)) > 0) {
        /* bytes contains how many bytes we can write to bio_ext */
        if (i_stream_read_data(ssl_io->plain_input,
                       &data, &size, 0) == -1 &&
            size == 0 && !bytes_read) {
            ssl_io->plain_stream_errno =
                ssl_io->plain_input->stream_errno;
            ssl_io->closed = TRUE;
            return FALSE;
        }
        if (size == 0) {
            /* wait for more input */
            break;
        }
        if (size > bytes)
            size = bytes;

        ret = BIO_write(ssl_io->bio_ext, data, size);
        i_assert(ret == (ssize_t)size);

        i_stream_skip(ssl_io->plain_input, size);
        bytes_read = TRUE;
    }
    if (bytes == 0 && !bytes_read && ssl_io->want_read) {
        /* shouldn't happen */
        i_panic("SSL BIO buffer size too small");
    }
    if (bytes_read) {
        if (ssl_io->ostream_flush_waiting_input) {
            ssl_io->ostream_flush_waiting_input = FALSE;
            o_stream_set_flush_pending(ssl_io->plain_output, TRUE);
        }
        ssl_io->want_read = FALSE;
    }
    return bytes_read;
}

bool ssl_iostream_bio_sync(struct ssl_iostream *ssl_io)
{
    bool ret;

    ret = ssl_iostream_bio_output(ssl_io);
    if (ssl_iostream_bio_input(ssl_io))
        ret = TRUE;
    return ret;
}

int ssl_iostream_more(struct ssl_iostream *ssl_io)
{
    int ret;

    if (!ssl_io->handshaked) {
        if ((ret = ssl_iostream_handshake(ssl_io)) <= 0)
            return ret;
    }
    (void)ssl_iostream_bio_sync(ssl_io);
    return 1;
}

static void ssl_iostream_set_error(struct ssl_iostream *ssl_io, const char *str)
{
    i_free(ssl_io->last_error);
    ssl_io->last_error = i_strdup(str);
}

static int
ssl_iostream_handle_error_full(struct ssl_iostream *ssl_io, int ret,
                   const char *func_name, bool write_error)
{
    const char *errstr = NULL;
    int err;

    err = SSL_get_error(ssl_io->ssl, ret);
    switch (err) {
    case SSL_ERROR_WANT_WRITE:
        if (!ssl_iostream_bio_sync(ssl_io)) {
            if (!write_error)
                i_panic("SSL ostream buffer size not unlimited");
            return 0;
        }
        if (ssl_io->closed) {
            errno = ssl_io->plain_stream_errno;
            return -1;
        }
        return 1;
    case SSL_ERROR_WANT_READ:
        ssl_io->want_read = TRUE;
        (void)ssl_iostream_bio_sync(ssl_io);
        if (ssl_io->closed) {
            errno = ssl_io->plain_stream_errno;
            return -1;
        }
        return ssl_io->want_read ? 0 : 1;
    case SSL_ERROR_SYSCALL:
        /* eat up the error queue */
        if (ERR_peek_error() != 0) {
            errstr = ssl_iostream_error();
            errno = EINVAL;
        } else if (ret != 0) {
            errstr = strerror(errno);
        } else {
            /* EOF. */
            errno = ECONNRESET;
            errstr = "Disconnected";
            break;
        }
        errstr = t_strdup_printf("%s syscall failed: %s",
                     func_name, errstr);
        break;
    case SSL_ERROR_ZERO_RETURN:
        /* clean connection closing */
        errno = ECONNRESET;
        break;
    case SSL_ERROR_SSL:
        errstr = t_strdup_printf("%s failed: %s",
                     func_name, ssl_iostream_error());
        errno = EINVAL;
        break;
    default:
        errstr = t_strdup_printf("%s failed: unknown failure %d (%s)",
                     func_name, err, ssl_iostream_error());
        errno = EINVAL;
        break;
    }

    if (errstr != NULL)
        ssl_iostream_set_error(ssl_io, errstr);
    return -1;
}

int ssl_iostream_handle_error(struct ssl_iostream *ssl_io, int ret,
                  const char *func_name)
{
    return ssl_iostream_handle_error_full(ssl_io, ret, func_name, FALSE);
}

int ssl_iostream_handle_write_error(struct ssl_iostream *ssl_io, int ret,
                    const char *func_name)
{
    return ssl_iostream_handle_error_full(ssl_io, ret, func_name, TRUE);
}

static const char *asn1_string_to_c(ASN1_STRING *asn_str)
{
    const char *cstr;
    unsigned int len;

    len = ASN1_STRING_length(asn_str);
    cstr = t_strndup(ASN1_STRING_data(asn_str), len);
    if (strlen(cstr) != len) {
        /* NULs in the name - could be some MITM attack.
           never allow. */
        return "";
    }
    return cstr;
}

static const char *get_general_dns_name(const GENERAL_NAME *name)
{
    if (ASN1_STRING_type(name->d.ia5) != V_ASN1_IA5STRING)
        return "";

    return asn1_string_to_c(name->d.ia5);
}

static const char *get_cname(X509 *cert)
{
    X509_NAME *name;
    X509_NAME_ENTRY *entry;
    ASN1_STRING *str;
    int cn_idx;

    name = X509_get_subject_name(cert);
    if (name == NULL)
        return "";
    cn_idx = X509_NAME_get_index_by_NID(name, NID_commonName, -1);
    if (cn_idx == -1)
        return "";
    entry = X509_NAME_get_entry(name, cn_idx);
    i_assert(entry != NULL);
    str = X509_NAME_ENTRY_get_data(entry);
    i_assert(str != NULL);
    return asn1_string_to_c(str);
}

int ssl_iostream_cert_match_name(struct ssl_iostream *ssl_io,
                 const char *verify_name)
{
    X509 *cert;
    STACK_OF(GENERAL_NAME) *gnames;
    const GENERAL_NAME *gn;
    const char *dnsname;
    bool dns_names = FALSE;
    unsigned int i, count;

    if (!ssl_iostream_has_valid_client_cert(ssl_io))
        return -1;

    cert = SSL_get_peer_certificate(ssl_io->ssl);
    i_assert(cert != NULL);

    /* verify against SubjectAltNames */
    gnames = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL);
    count = gnames == NULL ? 0 : sk_GENERAL_NAME_num(gnames);
    for (i = 0; i < count; i++) {
        gn = sk_GENERAL_NAME_value(gnames, i);
        if (gn->type == GEN_DNS) {
            dns_names = TRUE;
            dnsname = get_general_dns_name(gn);
            if (strcmp(dnsname, verify_name) == 0)
                break;
        }
    }
    sk_GENERAL_NAME_pop_free(gnames, GENERAL_NAME_free);
    /* verify against CommonName only when there wasn't any DNS
       SubjectAltNames */
    if (dns_names)
        return i < count ? 0 : -1;

    return strcmp(get_cname(cert), verify_name) == 0 ? 0 : -1;
}

int ssl_iostream_handshake(struct ssl_iostream *ssl_io)
{
    int ret;

    i_assert(!ssl_io->handshaked);

    if (ssl_io->ctx->client_ctx) {
        while ((ret = SSL_connect(ssl_io->ssl)) <= 0) {
            ret = ssl_iostream_handle_error(ssl_io, ret,
                            "SSL_connect()");
            if (ret <= 0)
                return ret;
        }
    } else {
        while ((ret = SSL_accept(ssl_io->ssl)) <= 0) {
            ret = ssl_iostream_handle_error(ssl_io, ret,
                            "SSL_accept()");
            if (ret <= 0)
                return ret;
        }
    }
    /* handshake finished */
    (void)ssl_iostream_bio_sync(ssl_io);

    i_free_and_null(ssl_io->last_error);
    ssl_io->handshaked = TRUE;

    if (ssl_io->handshake_callback != NULL) {
        if (ssl_io->handshake_callback(ssl_io->handshake_context) < 0) {
            errno = EINVAL;
            return -1;
        }
    }
    if (ssl_io->ssl_output != NULL)
        (void)o_stream_flush(ssl_io->ssl_output);
    return 1;
}

void ssl_iostream_set_handshake_callback(struct ssl_iostream *ssl_io,
                     int (*callback)(void *context),
                     void *context)
{
    ssl_io->handshake_callback = callback;
    ssl_io->handshake_context = context;
}

bool ssl_iostream_is_handshaked(const struct ssl_iostream *ssl_io)
{
    return ssl_io->handshaked;
}

bool ssl_iostream_has_valid_client_cert(const struct ssl_iostream *ssl_io)
{
    return ssl_io->cert_received && !ssl_io->cert_broken;
}

bool ssl_iostream_has_broken_client_cert(struct ssl_iostream *ssl_io)
{
    return ssl_io->cert_received && ssl_io->cert_broken;
}

const char *ssl_iostream_get_peer_name(struct ssl_iostream *ssl_io)
{
    X509 *x509;
    char *name;
    int len;

    if (!ssl_iostream_has_valid_client_cert(ssl_io))
        return NULL;

    x509 = SSL_get_peer_certificate(ssl_io->ssl);
    i_assert(x509 != NULL);

    len = X509_NAME_get_text_by_NID(X509_get_subject_name(x509),
                    ssl_io->username_nid, NULL, 0);
    if (len < 0)
        name = "";
    else {
        name = t_malloc(len + 1);
        if (X509_NAME_get_text_by_NID(X509_get_subject_name(x509),
                          ssl_io->username_nid,
                          name, len + 1) < 0)
            name = "";
        else if (strlen(name) != (size_t)len) {
            /* NUL characters in name. Someone's trying to fake
               being another user? Don't allow it. */
            name = "";
        }
    }
    X509_free(x509);

    return *name == '\0' ? NULL : name;
}

const char *ssl_iostream_get_security_string(struct ssl_iostream *ssl_io)
{
    const SSL_CIPHER *cipher;
#ifdef HAVE_SSL_COMPRESSION
    const COMP_METHOD *comp;
#endif
    const char *comp_str;
    int bits, alg_bits;

    if (!ssl_io->handshaked)
        return "";

    cipher = SSL_get_current_cipher(ssl_io->ssl);
    bits = SSL_CIPHER_get_bits(cipher, &alg_bits);
#ifdef HAVE_SSL_COMPRESSION
    comp = SSL_get_current_compression(ssl_io->ssl);
    comp_str = comp == NULL ? "" :
        t_strconcat(" ", SSL_COMP_get_name(comp), NULL);
#else
    comp_str = "";
#endif
    return t_strdup_printf("%s with cipher %s (%d/%d bits)%s",
                   SSL_get_version(ssl_io->ssl),
                   SSL_CIPHER_get_name(cipher),
                   bits, alg_bits, comp_str);
}

const char *ssl_iostream_get_last_error(struct ssl_iostream *ssl_io)
{
    return ssl_io->last_error;
}