rewrite SSL certificate verification. again.
leave all the hard work to OpenSSL. this has several consequences: - certificate chain validation actually works instead of throwing around error 20 - the interactive approval is gone. i don't expect it to be useful anyway, as mbsync is mostly a batch tool - the code is much shorter
This commit is contained in:
Oswald Buddenhagen
parent
d00d38836d
commit
acb1c870b4
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@ -67,8 +67,9 @@ typedef struct server_conf {
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unsigned use_tlsv12:1;
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/* these are actually variables and are leaked at the end */
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unsigned ssl_ctx_valid:1;
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unsigned num_trusted;
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SSL_CTX *SSLContext;
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X509_STORE *cert_store;
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#endif
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} server_conf_t;
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@ -87,6 +88,7 @@ typedef struct {
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char *name;
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#ifdef HAVE_LIBSSL
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SSL *ssl;
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int force_trusted;
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#endif
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void (*bad_callback)( void *aux ); /* async fail while sending or listening */
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11
src/mbsync.1
11
src/mbsync.1
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@ -273,8 +273,12 @@ established with the IMAP server. (Default: \fIyes\fR)
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..
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.TP
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\fBCertificateFile\fR \fIpath\fR
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File containing X.509 CA certificates used to verify server identities.
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This option is \fImandatory\fR if SSL is used. See \fBSSL CERTIFICATES\fR below.
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File containing additional X.509 certificates used to verify server
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identities. Directly matched peer certificates are always trusted,
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regardless of validity.
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.br
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Note that the system's default certificate store is always used and should
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not be specified here.
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..
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.TP
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\fBUseSSLv2\fR \fIyes\fR|\fIno\fR
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@ -507,9 +511,6 @@ disproportionate.
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\fBThorough\fR - this avoids message duplication after crashes as well,
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at some additional performance cost.
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..
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.SH SSL CERTIFICATES
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[to be done]
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..
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.SH INHERENT PROBLEMS
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Changes done after \fBmbsync\fR has retrieved the message list will not be
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synchronised until the next time \fBmbsync\fR is invoked.
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179
src/socket.c
179
src/socket.c
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@ -62,6 +62,8 @@ socket_fail( conn_t *conn )
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}
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#ifdef HAVE_LIBSSL
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static int ssl_data_idx;
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static int
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ssl_return( const char *func, conn_t *conn, int ret )
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{
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@ -99,26 +101,6 @@ ssl_return( const char *func, conn_t *conn, int ret )
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/* Some of this code is inspired by / lifted from mutt. */
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static int
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compare_certificates( X509 *cert, X509 *peercert,
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unsigned char *peermd, unsigned peermdlen )
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{
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unsigned char md[EVP_MAX_MD_SIZE];
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unsigned mdlen;
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/* Avoid CPU-intensive digest calculation if the certificates are
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* not even remotely equal. */
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if (X509_subject_name_cmp( cert, peercert ) ||
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X509_issuer_name_cmp( cert, peercert ))
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return -1;
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if (!X509_digest( cert, EVP_sha1(), md, &mdlen ) ||
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peermdlen != mdlen || memcmp( peermd, md, mdlen ))
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return -1;
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return 0;
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}
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static int
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host_matches( const char *host, const char *pattern )
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{
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@ -175,120 +157,45 @@ verify_hostname( X509 *cert, const char *hostname )
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return -1;
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}
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#if OPENSSL_VERSION_NUMBER >= 0x00904000L
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#define READ_X509_KEY(fp, key) PEM_read_X509( fp, key, 0, 0 )
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#else
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#define READ_X509_KEY(fp, key) PEM_read_X509( fp, key, 0 )
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#endif
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/* this gets called when a certificate is to be verified */
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static int
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verify_cert( const server_conf_t *conf, conn_t *sock )
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verify_cert_host( const server_conf_t *conf, conn_t *sock )
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{
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server_conf_t *mconf = (server_conf_t *)conf;
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SSL *ssl = sock->ssl;
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X509 *cert, *lcert;
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BIO *bio;
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FILE *fp;
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int err;
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unsigned n, i;
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X509_STORE_CTX xsc;
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char buf[256];
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unsigned char md[EVP_MAX_MD_SIZE];
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X509 *cert;
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cert = SSL_get_peer_certificate( ssl );
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if (!conf->host || sock->force_trusted > 0)
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return 0;
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cert = SSL_get_peer_certificate( sock->ssl );
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if (!cert) {
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error( "Error, no server certificate\n" );
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return -1;
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}
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while (conf->cert_file) { /* while() instead of if() so break works */
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/* Note: this code intentionally does no hostname verification. */
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return verify_hostname( cert, conf->host );
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}
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if (X509_cmp_current_time( X509_get_notBefore( cert )) >= 0) {
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error( "Server certificate is not yet valid\n" );
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break;
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}
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if (X509_cmp_current_time( X509_get_notAfter( cert )) <= 0) {
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error( "Server certificate has expired\n" );
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break;
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}
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if (!X509_digest( cert, EVP_sha1(), md, &n )) {
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error( "*** Unable to calculate digest\n" );
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break;
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}
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if (!(fp = fopen( conf->cert_file, "rt" ))) {
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sys_error( "Unable to load CertificateFile '%s'", conf->cert_file );
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return -1;
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}
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err = -1;
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for (lcert = 0; READ_X509_KEY( fp, &lcert ); )
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if (!(err = compare_certificates( lcert, cert, md, n ))) /* TODO: check X509v3 [Extended] Key Usage? */
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static int
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ssl_verify_callback( int ok, X509_STORE_CTX *ctx )
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{
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SSL *ssl = X509_STORE_CTX_get_ex_data( ctx, SSL_get_ex_data_X509_STORE_CTX_idx() );
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conn_t *conn = SSL_get_ex_data( ssl, ssl_data_idx );
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if (!conn->force_trusted) {
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X509 *cert = sk_X509_value( ctx->chain, 0 );
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STACK_OF(X509_OBJECT) *trusted = ctx->ctx->objs;
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unsigned i;
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conn->force_trusted = -1;
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for (i = 0; i < conn->conf->num_trusted; i++) {
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if (!X509_cmp( cert, sk_X509_OBJECT_value( trusted, i )->data.x509 )) {
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conn->force_trusted = 1;
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break;
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X509_free( lcert );
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fclose( fp );
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if (!err)
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return 0;
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break;
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}
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if (!mconf->cert_store) {
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if (!(mconf->cert_store = X509_STORE_new())) {
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error( "Error creating certificate store\n" );
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return -1;
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}
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if (!X509_STORE_set_default_paths( mconf->cert_store ))
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warn( "Error while loading default certificate files: %s\n",
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ERR_error_string( ERR_get_error(), 0 ) );
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if (!conf->cert_file) {
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info( "Note: CertificateFile not defined\n" );
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} else if (!X509_STORE_load_locations( mconf->cert_store, conf->cert_file, 0 )) {
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error( "Error while loading certificate file '%s': %s\n",
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conf->cert_file, ERR_error_string( ERR_get_error(), 0 ) );
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return -1;
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}
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}
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}
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X509_STORE_CTX_init( &xsc, mconf->cert_store, cert, 0 );
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err = X509_verify_cert( &xsc ) > 0 ? 0 : X509_STORE_CTX_get_error( &xsc );
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X509_STORE_CTX_cleanup( &xsc );
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if (err) {
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error( "Error, cannot verify certificate: %s (%d)\n",
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X509_verify_cert_error_string( err ), err );
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goto intcheck;
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}
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if (conf->host && verify_hostname( cert, conf->host ) < 0)
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goto intcheck;
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return 0;
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intcheck:
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X509_NAME_oneline( X509_get_subject_name( cert ), buf, sizeof(buf) );
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info( "\nSubject: %s\n", buf );
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X509_NAME_oneline( X509_get_issuer_name( cert ), buf, sizeof(buf) );
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info( "Issuer: %s\n", buf );
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bio = BIO_new( BIO_s_mem() );
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ASN1_TIME_print( bio, X509_get_notBefore( cert ) );
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memset( buf, 0, sizeof(buf) );
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BIO_read( bio, buf, sizeof(buf) - 1 );
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info( "Valid from: %s\n", buf );
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ASN1_TIME_print( bio, X509_get_notAfter( cert ) );
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memset( buf, 0, sizeof(buf) );
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BIO_read( bio, buf, sizeof(buf) - 1 );
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BIO_free( bio );
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info( " to: %s\n", buf );
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if (!X509_digest( cert, EVP_md5(), md, &n )) {
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error( "*** Unable to calculate fingerprint\n" );
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} else {
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info( "Fingerprint: " );
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for (i = 0; i < n; i += 2)
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info( "%02X%02X ", md[i], md[i + 1] );
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info( "\n" );
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}
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fputs( "\nAccept certificate? [y/N]: ", stderr );
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if (fgets( buf, sizeof(buf), stdin ) && (buf[0] == 'y' || buf[0] == 'Y'))
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return 0;
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return -1;
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if (conn->force_trusted > 0)
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ok = 1;
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return ok;
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}
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static int
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@ -297,6 +204,9 @@ init_ssl_ctx( const server_conf_t *conf )
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server_conf_t *mconf = (server_conf_t *)conf;
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int options = 0;
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if (conf->SSLContext)
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return conf->ssl_ctx_valid;
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mconf->SSLContext = SSL_CTX_new( SSLv23_client_method() );
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if (!conf->use_sslv2)
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@ -316,9 +226,20 @@ init_ssl_ctx( const server_conf_t *conf )
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SSL_CTX_set_options( mconf->SSLContext, options );
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/* we check the result of the verification after SSL_connect() */
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SSL_CTX_set_verify( mconf->SSLContext, SSL_VERIFY_NONE, 0 );
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return 0;
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if (conf->cert_file && !SSL_CTX_load_verify_locations( mconf->SSLContext, conf->cert_file, 0 )) {
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error( "Error while loading certificate file '%s': %s\n",
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conf->cert_file, ERR_error_string( ERR_get_error(), 0 ) );
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return 0;
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}
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mconf->num_trusted = sk_X509_OBJECT_num( SSL_CTX_get_cert_store( mconf->SSLContext )->objs );
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if (!SSL_CTX_set_default_verify_paths( mconf->SSLContext ))
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warn( "Warning: Unable to load default certificate files: %s\n",
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ERR_error_string( ERR_get_error(), 0 ) );
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SSL_CTX_set_verify( mconf->SSLContext, SSL_VERIFY_PEER, ssl_verify_callback );
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mconf->ssl_ctx_valid = 1;
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return 1;
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}
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static void start_tls_p2( conn_t * );
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@ -334,10 +255,11 @@ socket_start_tls( conn_t *conn, void (*cb)( int ok, void *aux ) )
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if (!ssl_inited) {
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SSL_library_init();
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SSL_load_error_strings();
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ssl_data_idx = SSL_get_ex_new_index( 0, NULL, NULL, NULL, NULL );
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ssl_inited = 1;
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}
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if (!conn->conf->SSLContext && init_ssl_ctx( conn->conf )) {
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if (!init_ssl_ctx( conn->conf )) {
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start_tls_p3( conn, 0 );
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return;
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}
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@ -345,6 +267,7 @@ socket_start_tls( conn_t *conn, void (*cb)( int ok, void *aux ) )
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conn->ssl = SSL_new( ((server_conf_t *)conn->conf)->SSLContext );
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SSL_set_fd( conn->ssl, conn->fd );
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SSL_set_mode( conn->ssl, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER );
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SSL_set_ex_data( conn->ssl, ssl_data_idx, conn );
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conn->state = SCK_STARTTLS;
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start_tls_p2( conn );
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}
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@ -359,8 +282,8 @@ start_tls_p2( conn_t *conn )
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case 0:
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break;
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default:
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/* verify the server certificate */
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if (verify_cert( conn->conf, conn )) {
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/* verify whether the server hostname matches the certificate */
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if (verify_cert_host( conn->conf, conn )) {
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start_tls_p3( conn, 0 );
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} else {
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info( "Connection is now encrypted\n" );
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