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libsec: sha256 support for thumbprint files, use it in ssh as well

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initThumbprints() now takes an application tag argument
so x509 and ssh can coexist.

the thumbprint entries can now hold both sha1 and sha256
hashes. okThumbprint() now takes a len argument for the
hash length used.

the new function okCertificate() hashes the certificate
with both and checks for any matches.

on failure, okCertificate() returns 0 and sets error string.

we also check for include loops now in thumbfiles, limiting
the number of includes to 8.
This commit is contained in:
cinap_lenrek 2017-04-23 19:00:08 +02:00
parent 2d1fbbdafa
commit 346f5828e0
11 changed files with 126 additions and 123 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
sys/include/ape/libsec.h
View file

@ -461,7 +461,8 @@ DSApriv* asn1toDSApriv(uchar*, int);
*/
typedef struct Thumbprint{
struct Thumbprint *next;
uchar sha1[SHA1dlen];
uchar hash[SHA2_256dlen];
uchar len;
} Thumbprint;
typedef struct TLSconn{
@ -487,9 +488,10 @@ int tlsClient(int fd, TLSconn *c);
int tlsServer(int fd, TLSconn *c);
/* thumb.c */
Thumbprint* initThumbprints(char *ok, char *crl);
Thumbprint* initThumbprints(char *ok, char *crl, char *tag);
void freeThumbprints(Thumbprint *ok);
int okThumbprint(uchar *sha1, Thumbprint *ok);
int okThumbprint(uchar *hash, int len, Thumbprint *ok);
int okCertificate(uchar *cert, int len, Thumbprint *ok);
/* readcert.c */
uchar *readcert(char *filename, int *pcertlen);

8
sys/include/libsec.h
View file

@ -453,7 +453,8 @@ DSApriv* asn1toDSApriv(uchar*, int);
*/
typedef struct Thumbprint{
struct Thumbprint *next;
uchar sha1[SHA1dlen];
uchar hash[SHA2_256dlen];
uchar len;
} Thumbprint;
typedef struct TLSconn{
@ -479,9 +480,10 @@ int tlsClient(int fd, TLSconn *c);
int tlsServer(int fd, TLSconn *c);
/* thumb.c */
Thumbprint* initThumbprints(char *ok, char *crl);
Thumbprint* initThumbprints(char *ok, char *crl, char *tag);
void freeThumbprints(Thumbprint *ok);
int okThumbprint(uchar *sha1, Thumbprint *ok);
int okThumbprint(uchar *hash, int len, Thumbprint *ok);
int okCertificate(uchar *cert, int len, Thumbprint *ok);
/* readcert.c */
uchar *readcert(char *filename, int *pcertlen);

16
sys/man/2/pushtls
View file

@ -1,6 +1,6 @@
.TH PUSHTLS 2
.SH NAME
pushtls, tlsClient, tlsServer, initThumbprints, freeThumbprints, okThumbprint, readcert, readcertchain \- attach TLS1 or SSL3 encryption to a communication channel
pushtls, tlsClient, tlsServer, initThumbprints, freeThumbprints, okThumbprint, okCertificate, readcert, readcertchain \- attach TLS1 or SSL3 encryption to a communication channel
.SH SYNOPSIS
.B #include <u.h>
.br
@ -29,13 +29,16 @@ uchar *readcert(char *filename, int *pcertlen)
PEMchain *readcertchain(char *filename)
.PP
.B
Thumbprint *initThumbprints(char *ok, char *crl)
Thumbprint *initThumbprints(char *ok, char *crl, char *tag)
.PP
.B
void freeThumbprints(Thumbprint *table)
.PP
.B
int okThumbprint(uchar *hash, Thumbprint *table)
int okThumbprint(uchar *hash, int len, Thumbprint *table)
.PP
.B
int okCertificate(uchar *cert, int len, Thumbprint *table)
.SH DESCRIPTION
Transport Layer Security (TLS) comprises a record layer protocol,
doing message digesting and encrypting in the kernel,
@ -213,13 +216,10 @@ be freed by the application whenever convenient.
Start the client half of TLS and check the remote certificate:
.IP
.EX
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");
if(!okCertificate(conn->cert, conn->certlen, table))
sysfatal("suspect server: %r");
\fI...application begins...\fP
.EE
.PP

18
sys/man/6/thumbprint
View file

@ -8,6 +8,8 @@ for example by calling
.B tlsClient
and
.B okThumbprint
or
.B okCertificate
(see
.IR pushtls (2)),
check the remote side's public key by comparing against
@ -25,13 +27,21 @@ attribute/value pairs of the form
.IB attr = value
or
.IR attr .
The first attribute must be
The first attribute must be the application tag:
.B x509
and the second must be
.BI sha1= {hex checksum of binary certificate}.
for tls applications or
.B ssh
for ssh server fingerprints.
The second attribute must be a hash type of
.B sha1=
or
.BI sha256=
followed by the hex or base64 encoded hash of binary certificate
or public key.
All other attributes are treated as comments.
The file may also contain lines of the form
.BI #include file
.B #include
.I file
.PP
For example, a web server might have thumbprint
.EX

2
sys/src/ape/lib/sec/mkfile
View file

@ -12,6 +12,7 @@ install all:V:
}
clean:V:
rm -f [$OS].* *.[$OS]
for(i in $DIRS)@{
echo $i
cd $i
@ -34,5 +35,6 @@ everything:V:
APE=/sys/src/ape
<$APE/config
$O.tlsclient: tlsclient.c
$CC -o $target $CFLAGS -D_POSIX_SOURCE -D_PLAN9_SOURCE -D_NET_EXTENSION tlsclient.c

11
sys/src/ape/lib/sec/tlsclient.c
View file

@ -107,7 +107,7 @@ main(int argc, char **argv)
sysfatal("specifying -x without -t is useless");
if(file){
thumb = initThumbprints(file, filex);
thumb = initThumbprints(file, filex, "x509");
if(thumb == nil)
sysfatal("initThumbprints: %r");
} else
@ -144,13 +144,8 @@ main(int argc, char **argv)
sysfatal("tlsclient: %r");
if(thumb){
uchar digest[20];
if(conn->cert==nil || conn->certlen<=0)
sysfatal("server did not provide TLS certificate");
sha1(conn->cert, conn->certlen, digest, nil);
if(!okThumbprint(digest, thumb))
sysfatal("server certificate %.*H not recognized", SHA1dlen, digest);
if(!okCertificate(conn->cert, conn->certlen, thumb))
sysfatal("cert for %s not recognized: %r", servername ? servername : addr);
freeThumbprints(thumb);
}

57
sys/src/cmd/ssh.c
View file

@ -4,7 +4,6 @@
#include <libsec.h>
#include <auth.h>
#include <authsrv.h>
#include <bio.h>
enum {
MSG_DISCONNECT = 1,
@ -84,7 +83,6 @@ char *user, *service, *status, *host, *cmd;
Oneway recv, send;
void dispatch(void);
int checkthumb(char*, uchar*);
void
shutdown(void)
@ -580,22 +578,25 @@ Next1: switch(recvpkt()){
ds = hashstr(ys, 32, ds);
if(thumb[0] == 0){
Thumbprint *ok;
sha2_256(ks, nks, h, nil);
i = snprint(thumb, sizeof(thumb), "%.*[", sizeof(h), h);
i = enc64(thumb, sizeof(thumb), h, sizeof(h));
while(i > 0 && thumb[i-1] == '=')
thumb[--i] = '\0';
i--;
thumb[i] = '\0';
if(debug)
fprint(2, "host fingerprint: %s\n", thumb);
switch(checkthumb(thumbfile, h)){
case 0:
werrstr("host unknown");
default:
ok = initThumbprints(thumbfile, nil, "ssh");
if(ok == nil || !okThumbprint(h, sizeof(h), ok)){
if(ok != nil) werrstr("unknown host");
fprint(2, "%s: %r, to add after verification:\n", argv0);
fprint(2, "\techo 'ssh sha256=%s # %s' >> %q\n", thumb, host, thumbfile);
fprint(2, "\techo 'ssh sha256=%s server=%s' >> %q\n", thumb, host, thumbfile);
sysfatal("checking hostkey failed: %r");
case 1:
break;
}
freeThumbprints(ok);
}
if((pub = ssh2rsapub(ks, nks)) == nil)
@ -1074,39 +1075,6 @@ rawon(void)
}
}
int
checkthumb(char *file, uchar hash[SHA2_256dlen])
{
uchar sum[SHA2_256dlen];
char *line, *field[50];
Biobuf *bin;
if((bin = Bopen(file, OREAD)) == nil)
return -1;
for(; (line = Brdstr(bin, '\n', 1)) != nil; free(line)){
if(tokenize(line, field, nelem(field)) < 2)
continue;
if(strcmp(field[0], "ssh") != 0 || strncmp(field[1], "sha256=", 7) != 0)
continue;
field[1] += 7;
if(dec64(sum, SHA2_256dlen, field[1], strlen(field[1])) != SHA2_256dlen){
werrstr("malformed ssh entry in %s: %s", file, field[1]);
goto err;
}
if(memcmp(sum, hash, SHA2_256dlen) == 0){
free(line);
Bterm(bin);
return 1;
}
}
Bterm(bin);
return 0;
err:
free(line);
Bterm(bin);
return -1;
}
void
usage(void)
{
@ -1124,7 +1092,6 @@ main(int argc, char *argv[])
quotefmtinstall();
fmtinstall('B', mpfmt);
fmtinstall('H', encodefmt);
fmtinstall('[', encodefmt);
s = getenv("TERM");
raw = s != nil && strcmp(s, "dumb") != 0;

11
sys/src/cmd/tlsclient.c
View file

@ -87,7 +87,7 @@ main(int argc, char **argv)
sysfatal("specifying -x without -t is useless");
if(file){
thumb = initThumbprints(file, filex);
thumb = initThumbprints(file, filex, "x509");
if(thumb == nil)
sysfatal("initThumbprints: %r");
} else
@ -123,13 +123,8 @@ main(int argc, char **argv)
sysfatal("tlsclient: %r");
if(thumb){
uchar digest[20];
if(conn->cert==nil || conn->certlen<=0)
sysfatal("server did not provide TLS certificate");
sha1(conn->cert, conn->certlen, digest, nil);
if(!okThumbprint(digest, thumb))
sysfatal("server certificate %.*H not recognized", SHA1dlen, digest);
if(!okCertificate(conn->cert, conn->certlen, thumb))
sysfatal("cert for %s not recognized: %r", servername ? servername : addr);
freeThumbprints(thumb);
}

13
sys/src/cmd/upas/fs/tls.c
View file

@ -6,7 +6,6 @@
int
wraptls(int ofd, char *host)
{
uchar digest[SHA1dlen];
Thumbprint *thumb;
TLSconn conn;
int fd;
@ -18,16 +17,10 @@ wraptls(int ofd, char *host)
close(ofd);
return -1;
}
thumb = initThumbprints("/sys/lib/tls/mail", "/sys/lib/tls/mail.exclude");
thumb = initThumbprints("/sys/lib/tls/mail", "/sys/lib/tls/mail.exclude", "x509");
if(thumb != nil){
if(conn.cert == nil || conn.certlen <= 0){
werrstr("server did not provide TLS certificate");
goto Err;
}
sha1(conn.cert, conn.certlen, digest, nil);
if(!okThumbprint(digest, thumb)){
werrstr("server certificate %.*H not recognized",
SHA1dlen, digest);
if(!okCertificate(conn.cert, conn.certlen, thumb)){
werrstr("cert for %s not recognized: %r", host);
Err:
close(fd);
fd = -1;

21
sys/src/cmd/upas/smtp/smtp.c
View file

@ -388,9 +388,8 @@ wraptls(void)
{
TLSconn *c;
Thumbprint *goodcerts;
char *h, *err;
char *err;
int fd;
uchar hash[SHA1dlen];
goodcerts = nil;
err = Giveup;
@ -412,29 +411,19 @@ wraptls(void)
Bterm(&bin);
Binit(&bin, fd, OREAD);
goodcerts = initThumbprints(smtpthumbs, smtpexclthumbs);
goodcerts = initThumbprints(smtpthumbs, smtpexclthumbs, "x509");
if (goodcerts == nil) {
syslog(0, "smtp", "bad thumbprints in %s", smtpthumbs);
goto Out;
}
/* compute sha1 hash of remote's certificate, see if we know it */
sha1(c->cert, c->certlen, hash, nil);
if (!okThumbprint(hash, goodcerts)) {
/* TODO? if not excluded, add hash to thumb list */
h = malloc(2*sizeof hash + 1);
if (h == nil)
goto Out;
enc16(h, 2*sizeof hash + 1, hash, sizeof hash);
syslog(0, "smtp", "remote cert. has bad thumbprint: x509 sha1=%s server=%q",
h, ddomain);
free(h);
if (!okCertificate(c->cert, c->certlen, goodcerts)) {
syslog(0, "smtp", "cert for %s not recognized: %r", ddomain);
goto Out;
}
syslog(0, "smtp", "started TLS to %q", ddomain);
err = nil;
Out:
if(goodcerts != nil)
freeThumbprints(goodcerts);
freeThumbprints(goodcerts);
free(c->cert);
free(c->sessionID);
free(c);

84
sys/src/libsec/port/thumb.c
View file

@ -5,9 +5,9 @@
enum{ ThumbTab = 1<<10 };
static Thumbprint*
tablehead(uchar *sum, Thumbprint *table)
tablehead(uchar *hash, Thumbprint *table)
{
return &table[((sum[0]<<8) + sum[1]) & (ThumbTab-1)];
return &table[((hash[0]<<8) + hash[1]) & (ThumbTab-1)];
}
void
@ -27,15 +27,15 @@ freeThumbprints(Thumbprint *table)
}
int
okThumbprint(uchar *sum, Thumbprint *table)
okThumbprint(uchar *hash, int len, Thumbprint *table)
{
Thumbprint *hd, *p;
if(table == nil)
return 0;
hd = tablehead(sum, table);
hd = tablehead(hash, table);
for(p = hd->next; p; p = p->next){
if(memcmp(sum, p->sha1, SHA1dlen) == 0)
if(p->len == len && memcmp(hash, p->hash, len) == 0)
return 1;
if(p == hd)
break;
@ -43,14 +43,51 @@ okThumbprint(uchar *sum, Thumbprint *table)
return 0;
}
int
okCertificate(uchar *cert, int len, Thumbprint *table)
{
uchar hash[SHA2_256dlen];
char thumb[2*SHA2_256dlen+1];
if(table == nil){
werrstr("no thumbprints provided");
return 0;
}
if(cert == nil || len <= 0){
werrstr("no certificate provided");
return 0;
}
sha1(cert, len, hash, nil);
if(okThumbprint(hash, SHA1dlen, table))
return 1;
sha2_256(cert, len, hash, nil);
if(okThumbprint(hash, SHA2_256dlen, table))
return 1;
len = enc64(thumb, sizeof(thumb), hash, SHA2_256dlen);
while(len > 0 && thumb[len-1] == '=')
len--;
thumb[len] = '\0';
werrstr("sha256=%s", thumb);
return 0;
}
static int
loadThumbprints(char *file, Thumbprint *table, Thumbprint *crltab)
loadThumbprints(char *file, char *tag, Thumbprint *table, Thumbprint *crltab, int depth)
{
Thumbprint *hd, *entry;
char *line, *field[50];
uchar sum[SHA1dlen];
uchar hash[SHA2_256dlen];
Biobuf *bin;
int len, n;
if(depth > 8){
werrstr("too many includes, last file %s", file);
return -1;
}
if(access(file, AEXIST) < 0)
return 0; /* not an error */
if((bin = Bopen(file, OREAD)) == nil)
@ -59,20 +96,30 @@ loadThumbprints(char *file, Thumbprint *table, Thumbprint *crltab)
if(tokenize(line, field, nelem(field)) < 2)
continue;
if(strcmp(field[0], "#include") == 0){
if(loadThumbprints(field[1], table, crltab) < 0)
if(loadThumbprints(field[1], tag, table, crltab, depth+1) < 0)
goto err;
continue;
}
if(strcmp(field[0], "x509") != 0 || strncmp(field[1], "sha1=", 5) != 0)
if(strcmp(field[0], tag) != 0)
continue;
field[1] += 5;
if(dec16(sum, SHA1dlen, field[1], strlen(field[1])) != SHA1dlen){
werrstr("malformed x509 entry in %s: %s", file, field[1]);
if(strncmp(field[1], "sha1=", 5) == 0){
field[1] += 5;
len = SHA1dlen;
} else if(strncmp(field[1], "sha256=", 7) == 0){
field[1] += 7;
len = SHA2_256dlen;
} else {
continue;
}
n = strlen(field[1]);
if((n != len*2 || dec16(hash, len, field[1], n) != len)
&& dec64(hash, len, field[1], n) != len){
werrstr("malformed %s entry in %s: %s", tag, file, field[1]);
goto err;
}
if(crltab && okThumbprint(sum, crltab))
if(crltab && okThumbprint(hash, len, crltab))
continue;
hd = tablehead(sum, table);
hd = tablehead(hash, table);
if(hd->next == nil)
entry = hd;
else {
@ -81,7 +128,8 @@ loadThumbprints(char *file, Thumbprint *table, Thumbprint *crltab)
entry->next = hd->next;
}
hd->next = entry;
memcpy(entry->sha1, sum, SHA1dlen);
entry->len = len;
memcpy(entry->hash, hash, len);
}
Bterm(bin);
return 0;
@ -92,7 +140,7 @@ err:
}
Thumbprint *
initThumbprints(char *ok, char *crl)
initThumbprints(char *ok, char *crl, char *tag)
{
Thumbprint *table, *crltab;
@ -101,13 +149,13 @@ initThumbprints(char *ok, char *crl)
if((crltab = malloc(ThumbTab * sizeof(*crltab))) == nil)
goto err;
memset(crltab, 0, ThumbTab * sizeof(*crltab));
if(loadThumbprints(crl, crltab, nil) < 0)
if(loadThumbprints(crl, tag, crltab, nil, 0) < 0)
goto err;
}
if((table = malloc(ThumbTab * sizeof(*table))) == nil)
goto err;
memset(table, 0, ThumbTab * sizeof(*table));
if(loadThumbprints(ok, table, crltab) < 0){
if(loadThumbprints(ok, tag, table, crltab, 0) < 0){
freeThumbprints(table);
table = nil;
}