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SecureTransport/DarwinSSL: Implement public key pinning
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@moparisthebest
moparisthebest committed Apr 17, 2017
1 parent ab6d232 commit 7251072
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Showing 4 changed files with 185 additions and 0 deletions.
4 changes: 4 additions & 0 deletions docs/libcurl/opts/CURLOPT_PINNEDPUBLICKEY.3
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Expand Up @@ -103,6 +103,8 @@ PEM/DER support:

7.49.0: PolarSSL

7.54.0: SecureTransport/DarwinSSL on macOS 10.7+/iOS 10+

sha256 support:

7.44.0: OpenSSL, GnuTLS, NSS and wolfSSL/CyaSSL
Expand All @@ -111,6 +113,8 @@ sha256 support:

7.49.0: PolarSSL

7.54.0: SecureTransport/DarwinSSL on macOS 10.7+/iOS 10+

Other SSL backends not supported.
.SH RETURN VALUE
Returns CURLE_OK if TLS enabled, CURLE_UNKNOWN_OPTION if not, or
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156 changes: 156 additions & 0 deletions lib/vtls/darwinssl.c
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Expand Up @@ -113,6 +113,36 @@
#define ioErr -36
#define paramErr -50

#ifdef DARWIN_SSL_PINNEDPUBKEY
/* both new and old APIs return rsa keys missing the spki header (not DER) */
static const unsigned char rsa4096SpkiHeader[] = {
0x30, 0x82, 0x02, 0x22, 0x30, 0x0d,
0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05,
0x00, 0x03, 0x82, 0x02, 0x0f, 0x00};

static const unsigned char rsa2048SpkiHeader[] = {
0x30, 0x82, 0x01, 0x22, 0x30, 0x0d,
0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05,
0x00, 0x03, 0x82, 0x01, 0x0f, 0x00};
#ifdef DARWIN_SSL_PINNEDPUBKEY_V1
/* the *new* version doesn't return DER encoded ecdsa certs like the old... */
static const unsigned char ecDsaSecp256r1SpkiHeader[] = {
0x30, 0x59, 0x30, 0x13, 0x06, 0x07,
0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02,
0x01, 0x06, 0x08, 0x2a, 0x86, 0x48,
0xce, 0x3d, 0x03, 0x01, 0x07, 0x03,
0x42, 0x00};

static const unsigned char ecDsaSecp384r1SpkiHeader[] = {
0x30, 0x76, 0x30, 0x10, 0x06, 0x07,
0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02,
0x01, 0x06, 0x05, 0x2b, 0x81, 0x04,
0x00, 0x22, 0x03, 0x62, 0x00};
#endif /* DARWIN_SSL_PINNEDPUBKEY_V1 */
#endif /* DARWIN_SSL_PINNEDPUBKEY */

/* The following two functions were ripped from Apple sample code,
* with some modifications: */
static OSStatus SocketRead(SSLConnectionRef connection,
Expand Down Expand Up @@ -1996,6 +2026,112 @@ static int verify_cert(const char *cafile, struct Curl_easy *data,
}
}

#ifdef DARWIN_SSL_PINNEDPUBKEY
static CURLcode pkp_pin_peer_pubkey(struct SessionHandle *data,
SSLContextRef ctx,
const char *pinnedpubkey)
{ /* Scratch */
size_t pubkeylen, realpubkeylen, spkiHeaderLength = 24;
unsigned char *pubkey = NULL, *realpubkey = NULL, *spkiHeader = NULL;
CFDataRef publicKeyBits = NULL;

/* Result is returned to caller */
CURLcode result = CURLE_SSL_PINNEDPUBKEYNOTMATCH;

/* if a path wasn't specified, don't pin */
if(!pinnedpubkey)
return CURLE_OK;


if(!ctx)
return result;

do {
SecTrustRef trust;
OSStatus ret = SSLCopyPeerTrust(ctx, &trust);
if(ret != noErr || trust == NULL)
break;

SecKeyRef keyRef = SecTrustCopyPublicKey(trust);
CFRelease(trust);
if(keyRef == NULL)
break;

#ifdef DARWIN_SSL_PINNEDPUBKEY_V1

publicKeyBits = SecKeyCopyExternalRepresentation(keyRef, NULL);
CFRelease(keyRef);
if(publicKeyBits == NULL)
break;

#elif DARWIN_SSL_PINNEDPUBKEY_V2

OSStatus success = SecItemExport(keyRef, kSecFormatOpenSSL, 0, NULL,
&publicKeyBits);
CFRelease(keyRef);
if(success != errSecSuccess || publicKeyBits == NULL)
break;

#endif /* DARWIN_SSL_PINNEDPUBKEY_V2 */

pubkeylen = CFDataGetLength(publicKeyBits);
pubkey = CFDataGetBytePtr(publicKeyBits);

switch(pubkeylen) {
case 526:
/* 4096 bit RSA pubkeylen == 526 */
spkiHeader = rsa4096SpkiHeader;
break;
case 270:
/* 2048 bit RSA pubkeylen == 270 */
spkiHeader = rsa2048SpkiHeader;
break;
#ifdef DARWIN_SSL_PINNEDPUBKEY_V1
case 65:
/* ecDSA secp256r1 pubkeylen == 65 */
spkiHeader = ecDsaSecp256r1SpkiHeader;
spkiHeaderLength = 26;
break;
case 97:
/* ecDSA secp384r1 pubkeylen == 97 */
spkiHeader = ecDsaSecp384r1SpkiHeader;
spkiHeaderLength = 23;
break;
default:
infof(data, "SSL: unhandled public key length: %d\n", pubkeylen);
#elif DARWIN_SSL_PINNEDPUBKEY_V2
default:
/* ecDSA secp256r1 pubkeylen == 91 header already included?
* ecDSA secp384r1 header already included too
* we assume rest of algorithms do same, so do nothing
*/
result = Curl_pin_peer_pubkey(data, pinnedpubkey, pubkey,
pubkeylen);
#endif /* DARWIN_SSL_PINNEDPUBKEY_V2 */
continue; /* break from loop */
}

realpubkeylen = pubkeylen + spkiHeaderLength;
realpubkey = malloc(realpubkeylen);
if(!realpubkey)
break;

memcpy(realpubkey, spkiHeader, spkiHeaderLength);
memcpy(realpubkey + spkiHeaderLength, pubkey, pubkeylen);

result = Curl_pin_peer_pubkey(data, pinnedpubkey, realpubkey,
realpubkeylen);

} while(0);

Curl_safefree(realpubkey);
if(publicKeyBits != NULL)
CFRelease(publicKeyBits);

return result;
}
#endif /* DARWIN_SSL_PINNEDPUBKEY */

static CURLcode
darwinssl_connect_step2(struct connectdata *conn, int sockindex)
{
Expand Down Expand Up @@ -2102,6 +2238,17 @@ darwinssl_connect_step2(struct connectdata *conn, int sockindex)
/* we have been connected fine, we're not waiting for anything else. */
connssl->connecting_state = ssl_connect_3;

#ifdef DARWIN_SSL_PINNEDPUBKEY
if(data->set.str[STRING_SSL_PINNEDPUBLICKEY_ORIG]) {
CURLcode result = pkp_pin_peer_pubkey(data, connssl->ssl_ctx,
data->set.str[STRING_SSL_PINNEDPUBLICKEY_ORIG]);
if(result) {
failf(data, "SSL: public key does not match pinned public key!");
return result;
}
}
#endif /* DARWIN_SSL_PINNEDPUBKEY */

/* Informational message */
(void)SSLGetNegotiatedCipher(connssl->ssl_ctx, &cipher);
(void)SSLGetNegotiatedProtocolVersion(connssl->ssl_ctx, &protocol);
Expand Down Expand Up @@ -2573,6 +2720,15 @@ void Curl_darwinssl_md5sum(unsigned char *tmp, /* input */
(void)CC_MD5(tmp, (CC_LONG)tmplen, md5sum);
}

void Curl_darwinssl_sha256sum(unsigned char *tmp, /* input */
size_t tmplen,
unsigned char *sha256sum, /* output */
size_t sha256len)
{
assert(sha256len >= SHA256_DIGEST_LENGTH);
(void)CC_SHA256(tmp, (CC_LONG)tmplen, sha256sum);
}

bool Curl_darwinssl_false_start(void)
{
#if CURL_BUILD_MAC_10_9 || CURL_BUILD_IOS_7
Expand Down
24 changes: 24 additions & 0 deletions lib/vtls/darwinssl.h
View file
Expand Up @@ -48,11 +48,34 @@ void Curl_darwinssl_md5sum(unsigned char *tmp, /* input */
size_t tmplen,
unsigned char *md5sum, /* output */
size_t md5len);
void Curl_darwinssl_sha256sum(unsigned char *tmp, /* input */
size_t tmplen,
unsigned char *sha256sum, /* output */
size_t sha256len);
bool Curl_darwinssl_false_start(void);

/* Set the API backend definition to SecureTransport */
#define CURL_SSL_BACKEND CURLSSLBACKEND_DARWINSSL

/* pinned public key support tests */

/* version 1 supports macOS 10.12+ and iOS 10+ */
#if ((TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED >= 100000) || \
(!TARGET_OS_IPHONE && __MAC_OS_X_VERSION_MIN_REQUIRED >= 101200))
#define DARWIN_SSL_PINNEDPUBKEY_V1 1
#endif

/* version 2 supports MacOSX 10.7+ */
#if (!TARGET_OS_IPHONE && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070)
#define DARWIN_SSL_PINNEDPUBKEY_V2 1
#endif

#if defined(DARWIN_SSL_PINNEDPUBKEY_V1) || defined(DARWIN_SSL_PINNEDPUBKEY_V2)
/* this backend supports CURLOPT_PINNEDPUBLICKEY */
#define DARWIN_SSL_PINNEDPUBKEY 1
#define have_curlssl_pinnedpubkey 1
#endif /* DARWIN_SSL_PINNEDPUBKEY */

/* API setup for SecureTransport */
#define curlssl_init() (1)
#define curlssl_cleanup() Curl_nop_stmt
Expand All @@ -70,6 +93,7 @@ bool Curl_darwinssl_false_start(void);
#define curlssl_data_pending(x,y) Curl_darwinssl_data_pending(x, y)
#define curlssl_random(x,y,z) ((void)x, Curl_darwinssl_random(y,z))
#define curlssl_md5sum(a,b,c,d) Curl_darwinssl_md5sum(a,b,c,d)
#define curlssl_sha256sum(a,b,c,d) Curl_darwinssl_sha256sum(a,b,c,d)
#define curlssl_false_start() Curl_darwinssl_false_start()

#endif /* USE_DARWINSSL */
Expand Down
1 change: 1 addition & 0 deletions tests/runtests.pl
View file
Expand Up @@ -2412,6 +2412,7 @@ sub checksystem {
}
elsif ($libcurl =~ /securetransport/i) {
$has_darwinssl=1;
$has_sslpinning=1;
$ssllib="DarwinSSL";
}
elsif ($libcurl =~ /BoringSSL/i) {
Expand Down

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