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From 11f1fd4b0d1b3aef5c79b843d081dbb9bcd0b85f Mon Sep 17 00:00:00 2001
From: Kurt Roeckx <kurt@roeckx.be>
Date: Tue, 15 Nov 2016 18:58:52 +0100
Subject: [PATCH] Make SSL_read and SSL_write return the old behaviour and
 document it.

Backport of beacb0f0c1ae7b0542fe053b95307f515b578eb7, revert of
122580ef71e4e5f355a1a104c9bfb36feee43759

Fixes: #1903

Reviewed-by: Matt Caswell <matt@openssl.org>

GH: #1966
---
 doc/ssl/SSL_get_error.pod | 22 +++++++++---------
 doc/ssl/SSL_read.pod      | 29 +++++++++---------------
 doc/ssl/SSL_write.pod     | 19 +++++++---------
 ssl/record/rec_layer_s3.c | 14 ++++--------
 test/asynciotest.c        | 57 ++++++++++++++++++++++++++++++++++-------------
 5 files changed, 75 insertions(+), 66 deletions(-)

diff --git a/doc/ssl/SSL_get_error.pod b/doc/ssl/SSL_get_error.pod
index ddd72f7..47d2358 100644
--- a/doc/ssl/SSL_get_error.pod
+++ b/doc/ssl/SSL_get_error.pod
@@ -38,12 +38,13 @@ if and only if B<ret E<gt> 0>.
 
 =item SSL_ERROR_ZERO_RETURN
 
-The TLS/SSL connection has been closed.  If the protocol version is SSL 3.0
-or TLS 1.0, this result code is returned only if a closure
-alert has occurred in the protocol, i.e. if the connection has been
-closed cleanly. Note that in this case B<SSL_ERROR_ZERO_RETURN>
-does not necessarily indicate that the underlying transport
-has been closed.
+The TLS/SSL connection has been closed.
+If the protocol version is SSL 3.0 or higher, this result code is returned only
+if a closure alert has occurred in the protocol, i.e. if the connection has been
+closed cleanly.
+Note that in this case B<SSL_ERROR_ZERO_RETURN> does not necessarily
+indicate that the underlying transport has been closed.
+
 
 =item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
 
@@ -111,12 +112,9 @@ thread has completed.
 
 =item SSL_ERROR_SYSCALL
 
-Some I/O error occurred.  The OpenSSL error queue may contain more
-information on the error.  If the error queue is empty
-(i.e. ERR_get_error() returns 0), B<ret> can be used to find out more
-about the error: If B<ret == 0>, an EOF was observed that violates
-the protocol.  If B<ret == -1>, the underlying B<BIO> reported an
-I/O error (for socket I/O on Unix systems, consult B<errno> for details).
+Some non-recoverable I/O error occurred.
+The OpenSSL error queue may contain more information on the error.
+For socket I/O on Unix systems, consult B<errno> for details.
 
 =item SSL_ERROR_SSL
 
diff --git a/doc/ssl/SSL_read.pod b/doc/ssl/SSL_read.pod
index 8dff244..20ccf40 100644
--- a/doc/ssl/SSL_read.pod
+++ b/doc/ssl/SSL_read.pod
@@ -81,28 +81,21 @@ The following return values can occur:
 
 =over 4
 
-=item E<gt>0
+=item E<gt> 0
 
-The read operation was successful; the return value is the number of
-bytes actually read from the TLS/SSL connection.
+The read operation was successful.
+The return value is the number of bytes actually read from the TLS/SSL
+connection.
 
-=item Z<>0
+=item Z<><= 0
 
-The read operation was not successful. The reason may either be a clean
-shutdown due to a "close notify" alert sent by the peer (in which case
-the SSL_RECEIVED_SHUTDOWN flag in the ssl shutdown state is set
-(see L<SSL_shutdown(3)>,
-L<SSL_set_shutdown(3)>). It is also possible, that
-the peer simply shut down the underlying transport and the shutdown is
-incomplete. Call SSL_get_error() with the return value B<ret> to find out,
-whether an error occurred or the connection was shut down cleanly
-(SSL_ERROR_ZERO_RETURN).
+The read operation was not successful, because either the connection was closed,
+an error occurred or action must be taken by the calling process.
+Call L<SSL_get_error(3)> with the return value B<ret> to find out the reason.
 
-=item E<lt>0
-
-The read operation was not successful, because either an error occurred
-or action must be taken by the calling process. Call SSL_get_error() with the
-return value B<ret> to find out the reason.
+Old documentation indicated a difference between 0 and -1, and that -1 was
+retryable.
+You should instead call SSL_get_error() to find out if it's retryable.
 
 =back
 
diff --git a/doc/ssl/SSL_write.pod b/doc/ssl/SSL_write.pod
index 5ab0790..ef3b92a 100644
--- a/doc/ssl/SSL_write.pod
+++ b/doc/ssl/SSL_write.pod
@@ -74,23 +74,20 @@ The following return values can occur:
 
 =over 4
 
-=item E<gt>0
+=item E<gt> 0
 
 The write operation was successful, the return value is the number of
 bytes actually written to the TLS/SSL connection.
 
-=item Z<>0
+=item Z<><= 0
 
-The write operation was not successful. Probably the underlying connection
-was closed. Call SSL_get_error() with the return value B<ret> to find out,
-whether an error occurred or the connection was shut down cleanly
-(SSL_ERROR_ZERO_RETURN).
+The write operation was not successful, because either the connection was
+closed, an error occurred or action must be taken by the calling process.
+Call SSL_get_error() with the return value B<ret> to find out the reason.
 
-=item E<lt>0
-
-The write operation was not successful, because either an error occurred
-or action must be taken by the calling process. Call SSL_get_error() with the
-return value B<ret> to find out the reason.
+Old documentation indicated a difference between 0 and -1, and that -1 was
+retryable.
+You should instead call SSL_get_error() to find out if it's retryable.
 
 =back
 
diff --git a/ssl/record/rec_layer_s3.c b/ssl/record/rec_layer_s3.c
index 28de7c3..1270a5f 100644
--- a/ssl/record/rec_layer_s3.c
+++ b/ssl/record/rec_layer_s3.c
@@ -178,10 +178,7 @@ const char *SSL_rstate_string(const SSL *s)
 }
 
 /*
- * Return values are as per SSL_read(), i.e.
- * >0 The number of read bytes
- *  0 Failure (not retryable)
- * <0 Failure (may be retryable)
+ * Return values are as per SSL_read()
  */
 int ssl3_read_n(SSL *s, int n, int max, int extend, int clearold)
 {
@@ -312,7 +309,7 @@ int ssl3_read_n(SSL *s, int n, int max, int extend, int clearold)
             if (s->mode & SSL_MODE_RELEASE_BUFFERS && !SSL_IS_DTLS(s))
                 if (len + left == 0)
                     ssl3_release_read_buffer(s);
-            return -1;
+            return i;
         }
         left += i;
         /*
@@ -882,10 +879,7 @@ int do_ssl3_write(SSL *s, int type, const unsigned char *buf,
 
 /* if s->s3->wbuf.left != 0, we need to call this
  *
- * Return values are as per SSL_read(), i.e.
- * >0 The number of read bytes
- *  0 Failure (not retryable)
- * <0 Failure (may be retryable)
+ * Return values are as per SSL_write()
  */
 int ssl3_write_pending(SSL *s, int type, const unsigned char *buf,
                        unsigned int len)
@@ -936,7 +930,7 @@ int ssl3_write_pending(SSL *s, int type, const unsigned char *buf,
                  */
                 SSL3_BUFFER_set_left(&wb[currbuf], 0);
             }
-            return -1;
+            return i;
         }
         SSL3_BUFFER_add_offset(&wb[currbuf], i);
         SSL3_BUFFER_add_left(&wb[currbuf], -i);
diff --git a/test/asynciotest.c b/test/asynciotest.c
index 0d382d7..133e3d5 100644
--- a/test/asynciotest.c
+++ b/test/asynciotest.c
@@ -297,32 +297,59 @@ int main(int argc, char *argv[])
          * we hit at least one async event in both reading and writing
          */
         for (j = 0; j < 2; j++) {
+            int len;
+
             /*
              * Write some test data. It should never take more than 2 attempts
-             * (the first one might be a retryable fail). A zero return from
-             * SSL_write() is a non-retryable failure, so fail immediately if
-             * we get that.
+             * (the first one might be a retryable fail).
              */
-            for (ret = -1, i = 0; ret < 0 && i < 2 * sizeof(testdata); i++)
-                ret = SSL_write(clientssl, testdata, sizeof(testdata));
-            if (ret <= 0) {
-                printf("Test %d failed: Failed to write app data\n", test);
+            for (ret = -1, i = 0, len = 0; len != sizeof(testdata) && i < 2;
+                i++) {
+                ret = SSL_write(clientssl, testdata + len,
+                    sizeof(testdata) - len);
+                if (ret > 0) {
+                    len += ret;
+                } else {
+                    int ssl_error = SSL_get_error(clientssl, ret);
+
+                    if (ssl_error == SSL_ERROR_SYSCALL ||
+                        ssl_error == SSL_ERROR_SSL) {
+                        printf("Test %d failed: Failed to write app data\n", test);
+                        err = -1;
+                        goto end;
+                    }
+                }
+            }
+            if (len != sizeof(testdata)) {
+                err = -1;
+                printf("Test %d failed: Failed to write all app data\n", test);
                 goto end;
             }
             /*
              * Now read the test data. It may take more attemps here because
              * it could fail once for each byte read, including all overhead
-             * bytes from the record header/padding etc. Fail immediately if we
-             * get a zero return from SSL_read().
+             * bytes from the record header/padding etc.
              */
-            for (ret = -1, i = 0; ret < 0 && i < MAX_ATTEMPTS; i++)
-                ret = SSL_read(serverssl, buf, sizeof(buf));
-            if (ret <= 0) {
-                printf("Test %d failed: Failed to read app data\n", test);
-                goto end;
+            for (ret = -1, i = 0, len = 0; len != sizeof(testdata) &&
+                i < MAX_ATTEMPTS; i++)
+            {
+                ret = SSL_read(serverssl, buf + len, sizeof(buf) - len);
+                if (ret > 0) {
+                    len += ret;
+                } else {
+                    int ssl_error = SSL_get_error(serverssl, ret);
+
+                    if (ssl_error == SSL_ERROR_SYSCALL ||
+                        ssl_error == SSL_ERROR_SSL) {
+                        printf("Test %d failed: Failed to read app data\n", test);
+                        err = -1;
+                        goto end;
+                    }
+                }
             }
-            if (ret != sizeof(testdata)
+            if (len != sizeof(testdata)
                     || memcmp(buf, testdata, sizeof(testdata)) != 0) {
+                err = -1;
                 printf("Test %d failed: Unexpected app data received\n", test);
                 goto end;
             }
-- 
2.5.5