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TLS_READ(3) Library Functions Manual TLS_READ(3) NAME tls_read, tls_write, tls_handshake, tls_error, tls_close, tls_reset -- use a TLS connection SYNOPSIS #include <tls.h> ssize_t tls_read(struct tls *ctx, void *buf, size_t buflen); ssize_t tls_write(struct tls *ctx, const void *buf, size_t buflen); int tls_handshake(struct tls *ctx); const char * tls_error(struct tls *ctx); int tls_close(struct tls *ctx); void tls_reset(struct tls *ctx); DESCRIPTION tls_read() reads buflen bytes of data from the socket into buf. It re- turns the amount of data read. tls_write() writes buflen bytes of data from buf to the socket. It re- turns the amount of data written. tls_handshake() explicitly performs the TLS handshake. It is only nec- essary to call this function if you need to guarantee that the hand- shake has completed, as both tls_read() and tls_write() automatically perform the TLS handshake when necessary. The tls_error() function may be used to retrieve a string containing more information about the most recent error relating to a context. tls_close() closes a connection after use. Only the TLS layer will be shut down and the caller is responsible for closing the file descrip- tors, unless the connection was established using tls_connect(3) or tls_connect_servername(3). After closing the connection, ctx can be passed to tls_free(3). RETURN VALUES tls_read() and tls_write() return a size on success or -1 on error. tls_handshake() and tls_close() return 0 on success or -1 on error. The tls_read(), tls_write(), tls_handshake(), and tls_close() functions also have two special return values: TLS_WANT_POLLIN The underlying read file descriptor needs to be readable in order to continue. TLS_WANT_POLLOUT The underlying write file descriptor needs to be writeable in order to continue. In the case of blocking file descriptors, the same function call should be repeated immediately. In the case of non-blocking file descriptors, the same function call should be repeated when the required condition has been met. Callers of these functions cannot rely on the value of the global errno. To prevent mishandling of error conditions, tls_read(), tls_write(), tls_handshake(), and tls_close() all explicitly clear errno. tls_error() returns NULL if no error occurred with ctx during or since the last call to tls_handshake(), tls_read(), tls_write(), tls_close(), or tls_reset() involving ctx, or if memory allocation failed while try- ing to assemble the string describing the most recent error related to ctx. EXAMPLES The following example demonstrates how to handle TLS writes on a block- ing file descriptor: ... while (len > 0) { ssize_t ret; ret = tls_write(ctx, buf, len); if (ret == TLS_WANT_POLLIN || ret == TLS_WANT_POLLOUT) continue; if (ret == -1) errx(1, "tls_write: %s", tls_error(ctx)); buf += ret; len -= ret; } ... The following example demonstrates how to handle TLS writes on a non- blocking file descriptor using poll(2): ... pfd[0].fd = fd; pfd[0].events = POLLIN|POLLOUT; while (len > 0) { nready = poll(pfd, 1, 0); if (nready == -1) err(1, "poll"); if ((pfd[0].revents & (POLLERR|POLLNVAL))) errx(1, "bad fd %d", pfd[0].fd); if ((pfd[0].revents & (pfd[0].events|POLLHUP))) { ssize_t ret; ret = tls_write(ctx, buf, len); if (ret == TLS_WANT_POLLIN) pfd[0].events = POLLIN; else if (ret == TLS_WANT_POLLOUT) pfd[0].events = POLLOUT; else if (ret == -1) errx(1, "tls_write: %s", tls_error(ctx)); else { buf += ret; len -= ret; } } } ... SEE ALSO tls_accept_socket(3), tls_configure(3), tls_conn_version(3), tls_connect(3), tls_init(3), tls_ocsp_process_response(3) HISTORY tls_read(), tls_write(), tls_error(), tls_close(), and tls_reset() ap- peared in OpenBSD 5.6 and got their final names in OpenBSD 5.7. tls_handshake() appeared in OpenBSD 5.9. AUTHORS Joel Sing <jsing@openbsd.org> with contributions from Bob Beck <beck@openbsd.org> CAVEATS The function tls_error() returns an internal pointer. It must not be freed by the application, or a double free error will occur. The pointer will become invalid when the next error occurs with ctx. Con- sequently, if the application may need the message at a later time, it has to copy the string before calling the next libtls function involv- ing ctx, or a segmentation fault or read access to unintended data is the likely result. FreeBSD Ports 14.quarterly July 9, 2019 TLS_READ(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS | CAVEATS
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