thodg/libgit2/src/streams/stransport.c

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• Hash : 5265b31c
  Author :
  Date : 2019-01-23T15:00:20
  

  streams: fix callers potentially only writing partial data Similar to the write(3) function, implementations of `git_stream_write` do not guarantee that all bytes are written. Instead, they return the number of bytes that actually have been written, which may be smaller than the total number of bytes. Furthermore, due to an interface design issue, we cannot ever write more than `SSIZE_MAX` bytes at once, as otherwise we cannot represent the number of bytes written to the caller. Unfortunately, no caller of `git_stream_write` ever checks the return value, except to verify that no error occurred. Due to this, they are susceptible to the case where only partial data has been written. Fix this by introducing a new function `git_stream__write_full`. In contrast to `git_stream_write`, it will always return either success or failure, without returning the number of bytes written. Thus, it is able to write all `SIZE_MAX` bytes and loop around `git_stream_write` until all data has been written. Adjust all callers except the BIO callbacks in our mbedtls and OpenSSL streams, which already do the right thing and require the amount of bytes written.

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• src/streams/stransport.c

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include "streams/stransport.h"
  
  #ifdef GIT_SECURE_TRANSPORT
  
  #include <CoreFoundation/CoreFoundation.h>
  #include <Security/SecureTransport.h>
  #include <Security/SecCertificate.h>
  
  #include "git2/transport.h"
  
  #include "streams/socket.h"
  
  static int stransport_error(OSStatus ret)
  {
  	CFStringRef message;
  
  	if (ret == noErr || ret == errSSLClosedGraceful) {
  		git_error_clear();
  		return 0;
  	}
  
  #if !TARGET_OS_IPHONE
  	message = SecCopyErrorMessageString(ret, NULL);
  	GIT_ERROR_CHECK_ALLOC(message);
  
  	git_error_set(GIT_ERROR_NET, "SecureTransport error: %s", CFStringGetCStringPtr(message, kCFStringEncodingUTF8));
  	CFRelease(message);
  #else
  	git_error_set(GIT_ERROR_NET, "SecureTransport error: OSStatus %d", (unsigned int)ret);
  	GIT_UNUSED(message);
  #endif
  
  	return -1;
  }
  
  typedef struct {
  	git_stream parent;
  	git_stream *io;
  	int owned;
  	SSLContextRef ctx;
  	CFDataRef der_data;
  	git_cert_x509 cert_info;
  } stransport_stream;
  
  static int stransport_connect(git_stream *stream)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  	int error;
  	SecTrustRef trust = NULL;
  	SecTrustResultType sec_res;
  	OSStatus ret;
  
  	if (st->owned && (error = git_stream_connect(st->io)) < 0)
  		return error;
  
  	ret = SSLHandshake(st->ctx);
  	if (ret != errSSLServerAuthCompleted) {
  		git_error_set(GIT_ERROR_SSL, "unexpected return value from ssl handshake %d", (int)ret);
  		return -1;
  	}
  
  	if ((ret = SSLCopyPeerTrust(st->ctx, &trust)) != noErr)
  		goto on_error;
  
  	if (!trust)
  		return GIT_ECERTIFICATE;
  
  	if ((ret = SecTrustEvaluate(trust, &sec_res)) != noErr)
  		goto on_error;
  
  	CFRelease(trust);
  
  	if (sec_res == kSecTrustResultInvalid || sec_res == kSecTrustResultOtherError) {
  		git_error_set(GIT_ERROR_SSL, "internal security trust error");
  		return -1;
  	}
  
  	if (sec_res == kSecTrustResultDeny || sec_res == kSecTrustResultRecoverableTrustFailure ||
  	    sec_res == kSecTrustResultFatalTrustFailure) {
  		git_error_set(GIT_ERROR_SSL, "untrusted connection error");
  		return GIT_ECERTIFICATE;
  	}
  
  	return 0;
  
  on_error:
  	if (trust)
  		CFRelease(trust);
  
  	return stransport_error(ret);
  }
  
  static int stransport_certificate(git_cert **out, git_stream *stream)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  	SecTrustRef trust = NULL;
  	SecCertificateRef sec_cert;
  	OSStatus ret;
  
  	if ((ret = SSLCopyPeerTrust(st->ctx, &trust)) != noErr)
  		return stransport_error(ret);
  
  	sec_cert = SecTrustGetCertificateAtIndex(trust, 0);
  	st->der_data = SecCertificateCopyData(sec_cert);
  	CFRelease(trust);
  
  	if (st->der_data == NULL) {
  		git_error_set(GIT_ERROR_SSL, "retrieved invalid certificate data");
  		return -1;
  	}
  
  	st->cert_info.parent.cert_type = GIT_CERT_X509;
  	st->cert_info.data = (void *) CFDataGetBytePtr(st->der_data);
  	st->cert_info.len = CFDataGetLength(st->der_data);
  
  	*out = (git_cert *)&st->cert_info;
  	return 0;
  }
  
  static int stransport_set_proxy(
  	git_stream *stream,
  	const git_proxy_options *proxy_opts)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  
  	return git_stream_set_proxy(st->io, proxy_opts);
  }
  
  /*
   * Contrary to typical network IO callbacks, Secure Transport write callback is
   * expected to write *all* passed data, not just as much as it can, and any
   * other case would be considered a failure.
   *
   * This behavior is actually not specified in the Apple documentation, but is
   * required for things to work correctly (and incidentally, that's also how
   * Apple implements it in its projects at opensource.apple.com).
   *
   * Libgit2 streams happen to already have this very behavior so this is just
   * passthrough.
   */
  static OSStatus write_cb(SSLConnectionRef conn, const void *data, size_t *len)
  {
  	git_stream *io = (git_stream *) conn;
  
  	if (git_stream__write_full(io, data, *len, 0) < 0)
  		return -36; /* "ioErr" from MacErrors.h which is not available on iOS */
  
  	return noErr;
  }
  
  static ssize_t stransport_write(git_stream *stream, const char *data, size_t len, int flags)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  	size_t data_len, processed;
  	OSStatus ret;
  
  	GIT_UNUSED(flags);
  
  	data_len = min(len, SSIZE_MAX);
  	if ((ret = SSLWrite(st->ctx, data, data_len, &processed)) != noErr)
  		return stransport_error(ret);
  
  	assert(processed < SSIZE_MAX);
  	return (ssize_t)processed;
  }
  
  /*
   * Contrary to typical network IO callbacks, Secure Transport read callback is
   * expected to read *exactly* the requested number of bytes, not just as much
   * as it can, and any other case would be considered a failure.
   *
   * This behavior is actually not specified in the Apple documentation, but is
   * required for things to work correctly (and incidentally, that's also how
   * Apple implements it in its projects at opensource.apple.com).
   */
  static OSStatus read_cb(SSLConnectionRef conn, void *data, size_t *len)
  {
  	git_stream *io = (git_stream *) conn;
  	OSStatus error = noErr;
  	size_t off = 0;
  	ssize_t ret;
  
  	do {
  		ret = git_stream_read(io, data + off, *len - off);
  		if (ret < 0) {
  			error = -36; /* "ioErr" from MacErrors.h which is not available on iOS */
  			break;
  		}
  		if (ret == 0) {
  			error = errSSLClosedGraceful;
  			break;
  		}
  
  		off += ret;
  	} while (off < *len);
  
  	*len = off;
  	return error;
  }
  
  static ssize_t stransport_read(git_stream *stream, void *data, size_t len)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  	size_t processed;
  	OSStatus ret;
  
  	if ((ret = SSLRead(st->ctx, data, len, &processed)) != noErr)
  		return stransport_error(ret);
  
  	return processed;
  }
  
  static int stransport_close(git_stream *stream)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  	OSStatus ret;
  
  	ret = SSLClose(st->ctx);
  	if (ret != noErr && ret != errSSLClosedGraceful)
  		return stransport_error(ret);
  
  	return st->owned ? git_stream_close(st->io) : 0;
  }
  
  static void stransport_free(git_stream *stream)
  {
  	stransport_stream *st = (stransport_stream *) stream;
  
  	if (st->owned)
  		git_stream_free(st->io);
  
  	CFRelease(st->ctx);
  	if (st->der_data)
  		CFRelease(st->der_data);
  	git__free(st);
  }
  
  static int stransport_wrap(
  	git_stream **out,
  	git_stream *in,
  	const char *host,
  	int owned)
  {
  	stransport_stream *st;
  	OSStatus ret;
  
  	assert(out && in && host);
  
  	st = git__calloc(1, sizeof(stransport_stream));
  	GIT_ERROR_CHECK_ALLOC(st);
  
  	st->io = in;
  	st->owned = owned;
  
  	st->ctx = SSLCreateContext(NULL, kSSLClientSide, kSSLStreamType);
  	if (!st->ctx) {
  		git_error_set(GIT_ERROR_NET, "failed to create SSL context");
  		git__free(st);
  		return -1;
  	}
  
  	if ((ret = SSLSetIOFuncs(st->ctx, read_cb, write_cb)) != noErr ||
  	    (ret = SSLSetConnection(st->ctx, st->io)) != noErr ||
  	    (ret = SSLSetSessionOption(st->ctx, kSSLSessionOptionBreakOnServerAuth, true)) != noErr ||
  	    (ret = SSLSetProtocolVersionMin(st->ctx, kTLSProtocol1)) != noErr ||
  	    (ret = SSLSetProtocolVersionMax(st->ctx, kTLSProtocol12)) != noErr ||
  	    (ret = SSLSetPeerDomainName(st->ctx, host, strlen(host))) != noErr) {
  		CFRelease(st->ctx);
  		git__free(st);
  		return stransport_error(ret);
  	}
  
  	st->parent.version = GIT_STREAM_VERSION;
  	st->parent.encrypted = 1;
  	st->parent.proxy_support = git_stream_supports_proxy(st->io);
  	st->parent.connect = stransport_connect;
  	st->parent.certificate = stransport_certificate;
  	st->parent.set_proxy = stransport_set_proxy;
  	st->parent.read = stransport_read;
  	st->parent.write = stransport_write;
  	st->parent.close = stransport_close;
  	st->parent.free = stransport_free;
  
  	*out = (git_stream *) st;
  	return 0;
  }
  
  int git_stransport_stream_wrap(
  	git_stream **out,
  	git_stream *in,
  	const char *host)
  {
  	return stransport_wrap(out, in, host, 0);
  }
  
  int git_stransport_stream_new(git_stream **out, const char *host, const char *port)
  {
  	git_stream *stream = NULL;
  	int error;
  
  	assert(out && host);
  
  	error = git_socket_stream_new(&stream, host, port);
  
  	if (!error)
  		error = stransport_wrap(out, stream, host, 1);
  
  	if (error < 0 && stream) {
  		git_stream_close(stream);
  		git_stream_free(stream);
  	}
  
  	return error;
  }
  
  #endif
  

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