PUSHTLS(3) PUSHTLS(3) NAME pushtls, tlsClient, tlsServer, initThumbprints, freeThumbprints, okThumbprint, readcert, readcertchain - attach TLS1 or SSL3 encryption to a communication channel SYNOPSIS #include <u.h> #include <libc.h> int pushtls(int fd, char *hashalg, char *encalg, int isclient, char *secret, char *dir) #include <mp.h> #include <libsec.h> int tlsClient(int fd, TLSconn *conn) int tlsServer(int fd, TLSconn *conn) uchar *readcert(char *filename, int *pcertlen) PEMchain *readcertchain(char *filename) Thumbprint* initThumbprints(char *ok, char *crl) void freeThumbprints(Thumbprint *table) int okThumbprint(uchar *hash, Thumbprint *table) DESCRIPTION Transport Layer Security (TLS) comprises a record layer pro- tocol, doing message digesting and encrypting in the kernel, and a handshake protocol, doing initial authentication and secret creation at user level and then starting a data chan- nel in the record protocol. TLS is nearly the same as SSL 3.0, and the software should interoperate with implementa- tions of either standard. To use just the record layer, as described in Plan 9's tls(3), call pushtls to open the record layer device, con- nect to the communications channel fd, and start up encryp- tion and message authentication as specified in hashalg, encalg, and secret. These parameters must have been arranged at the two ends of the conversation by other means. For example, hashalg could be sha1, encalg could be rc4_128, and secret could be the base-64 encoding of two (client-to- server and server-to-client) 20-byte digest keys and two corresponding 16-byte encryption keys. Pushtls returns a file descriptor for the TLS data channel. Anything written to this descriptor will get encrypted and authenticated and Page 1 Plan 9 (printed 3/11/25) PUSHTLS(3) PUSHTLS(3) then written to the file descriptor, fd. If dir is non-zero, the path name of the connection directory is copied into dir. This path name is guaranteed to be less than 40 bytes long. Alternatively, call tlsClient to speak the full handshake protocol, negotiate the algorithms and secrets, and return a new data file descriptor for the data channel. Conn points to a (caller-allocated) struct typedef struct TLSconn{ char dir[40]; // OUT connection directory uchar *cert; // IN/OUT certificate uchar *sessionID; // IN/OUT sessionID int certlen, sessionIDlen; void (*trace)(char*fmt, ...); PEMChain *chain; } TLSconn; defined in tls.h. On input, the caller can provide options such as cert, the local certificate, and sessionID, used by a client to resume a previously negotiated security associa- tion. On output, the connection directory is set, as with listen (see dial(3)). The input cert is freed and a freshly allocated copy of the remote's certificate is returned in conn, to be checked by the caller according to its needs. One mechanism is supplied by initThumbprints and freeThumbprints which allocate and free, respectively, a table of hashes from files of known trusted and revoked cer- tificates. okThumbprint confirms that a particular hash is in the table, as computed by uchar hash[SHA1dlen]; conn = (TLSconn*)mallocz(sizeof *conn, 1); fd = tlsClient(fd, conn); sha1(conn->cert, conn->certlen, hash, nil); if(!okThumbprint(hash,table)) exits("suspect server"); ...application begins... Call tlsServer to perform the corresponding function on the server side: fd = accept(lcfd, ldir); conn = (TLSconn*)mallocz(sizeof *conn, 1); conn->cert = readcert("cert.pem", &conn->certlen); fd = tlsServer(fd, conn); ...application begins... The private key corresponding to cert.pem should have been previously loaded into factotum. (See rsa(3) for more about key generation.) By setting conn->chain = readcertchain("intermediate-certs.pem"); the server can present extra certificate evidence to estab- lish the chain of trust to a root authority known to the Page 2 Plan 9 (printed 3/11/25) PUSHTLS(3) PUSHTLS(3) client. Conn is not required for the ongoing conversation and may be freed by the application whenever convenient. FILES /sys/lib/tls thumbprints of trusted services /sys/lib/ssl PEM certificate files SOURCE /usr/local/plan9/src/libsec/port SEE ALSO dial(3), thumbprint(7); Plan 9's factotum(4) and tls(3) DIAGNOSTICS return -1 on failure. BUGS Pushtls is not implemented. Client certificates and client sessionIDs are not yet imple- mented. Note that in the TLS protocol sessionID itself is public; it is used as a pointer to secrets stored in factotum. Page 3 Plan 9 (printed 3/11/25)