A file containing the trusted CA certificates needs to be supplied via the ca_file AVOption, unless the TLS library has got a system default file/database set up.
This doesn't check the hostname of the peer certificate with openssl, which requires a non-trivial piece of code for manually matching the desired hostname to the string provided by the certificate, not provided as a library function. That is, with openssl, this only validates that the received certificate is signed with the right CA, but not that it is the actual server we think we're talking to. Verification is still disabled by default since we can't count on a proper CA database existing at all times. --- Added support for gnutls_certificate_set_x509_system_trust and some other minor fixes. --- libavformat/tls.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 69 insertions(+), 1 deletion(-) diff --git a/libavformat/tls.c b/libavformat/tls.c index fecf096..55b7416 100644 --- a/libavformat/tls.c +++ b/libavformat/tls.c @@ -22,8 +22,10 @@ #include "avformat.h" #include "url.h" #include "libavutil/avstring.h" +#include "libavutil/opt.h" #if CONFIG_GNUTLS #include <gnutls/gnutls.h> +#include <gnutls/x509.h> #define TLS_read(c, buf, size) gnutls_record_recv(c->session, buf, size) #define TLS_write(c, buf, size) gnutls_record_send(c->session, buf, size) #define TLS_shutdown(c) gnutls_bye(c->session, GNUTLS_SHUT_RDWR) @@ -65,8 +67,26 @@ typedef struct { SSL *ssl; #endif int fd; + char *ca_file; + int verify; } TLSContext; +#define OFFSET(x) offsetof(TLSContext, x) +#define D AV_OPT_FLAG_DECODING_PARAM +#define E AV_OPT_FLAG_ENCODING_PARAM +static const AVOption options[] = { + {"ca_file", "Certificate Authority database file", OFFSET(ca_file), AV_OPT_TYPE_STRING, .flags = D|E }, + {"tls_verify", "Verify the peer certificate", OFFSET(verify), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, .flags = D|E }, + { NULL } +}; + +static const AVClass tls_class = { + .class_name = "tls", + .item_name = av_default_item_name, + .option = options, + .version = LIBAVUTIL_VERSION_INT, +}; + static int do_tls_poll(URLContext *h, int ret) { TLSContext *c = h->priv_data; @@ -108,6 +128,11 @@ static int tls_open(URLContext *h, const char *uri, int flags) TLSContext *c = h->priv_data; int ret; int port; +#if CONFIG_GNUTLS + unsigned int status, cert_list_size; + gnutls_x509_crt_t cert; + const gnutls_datum_t *cert_list; +#endif char buf[200], host[200]; int numerichost = 0; struct addrinfo hints = { 0 }, *ai = NULL; @@ -151,7 +176,14 @@ static int tls_open(URLContext *h, const char *uri, int flags) if (!numerichost) gnutls_server_name_set(c->session, GNUTLS_NAME_DNS, host, strlen(host)); gnutls_certificate_allocate_credentials(&c->cred); - gnutls_certificate_set_verify_flags(c->cred, 0); + if (c->ca_file) + gnutls_certificate_set_x509_trust_file(c->cred, c->ca_file, GNUTLS_X509_FMT_PEM); +#if GNUTLS_VERSION_MAJOR >= 3 + else + gnutls_certificate_set_x509_system_trust(c->cred); +#endif + gnutls_certificate_set_verify_flags(c->cred, c->verify ? + GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT : 0); gnutls_credentials_set(c->session, GNUTLS_CRD_CERTIFICATE, c->cred); gnutls_transport_set_ptr(c->session, (gnutls_transport_ptr_t) (intptr_t) c->fd); @@ -163,6 +195,35 @@ static int tls_open(URLContext *h, const char *uri, int flags) if ((ret = do_tls_poll(h, ret)) < 0) goto fail; } + if (c->verify) { + if ((ret = gnutls_certificate_verify_peers2(c->session, &status)) < 0) { + av_log(h, AV_LOG_ERROR, "Unable to verify peer certificate: %s\n", + gnutls_strerror(ret)); + ret = AVERROR(EIO); + goto fail; + } + if (status & GNUTLS_CERT_INVALID) { + av_log(h, AV_LOG_ERROR, "Peer certificate failed verification\n"); + ret = AVERROR(EIO); + goto fail; + } + if (gnutls_certificate_type_get(c->session) != GNUTLS_CRT_X509) { + av_log(h, AV_LOG_ERROR, "Unsupported certificate type\n"); + ret = AVERROR(EIO); + goto fail; + } + gnutls_x509_crt_init(&cert); + cert_list = gnutls_certificate_get_peers(c->session, &cert_list_size); + gnutls_x509_crt_import(cert, cert_list, GNUTLS_X509_FMT_DER); + ret = gnutls_x509_crt_check_hostname(cert, host); + gnutls_x509_crt_deinit(cert); + if (!ret) { + av_log(h, AV_LOG_ERROR, "The certificate's owner does not match " + "hostname %s\n", host); + ret = AVERROR(EIO); + goto fail; + } + } #elif CONFIG_OPENSSL c->ctx = SSL_CTX_new(TLSv1_client_method()); if (!c->ctx) { @@ -170,6 +231,12 @@ static int tls_open(URLContext *h, const char *uri, int flags) ret = AVERROR(EIO); goto fail; } + if (c->ca_file) + SSL_CTX_load_verify_locations(c->ctx, c->ca_file, NULL); + // Note, this doesn't check that the peer certificate actually matches + // the requested hostname. + if (c->verify) + SSL_CTX_set_verify(c->ctx, SSL_VERIFY_PEER, NULL); c->ssl = SSL_new(c->ctx); if (!c->ssl) { av_log(h, AV_LOG_ERROR, "%s\n", ERR_error_string(ERR_get_error(), NULL)); @@ -249,4 +316,5 @@ URLProtocol ff_tls_protocol = { .url_close = tls_close, .priv_data_size = sizeof(TLSContext), .flags = URL_PROTOCOL_FLAG_NETWORK, + .priv_data_class = &tls_class, }; -- 1.7.9.4 _______________________________________________ libav-devel mailing list libav-devel@libav.org https://lists.libav.org/mailman/listinfo/libav-devel