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Add a comment about final empty extension intolerance.

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We reordered extensions some time ago to ensure a non-empty extension was last,
but the comment was since lost (or I forgot to put one in in the first place).
Add one now so we don't regress.

Change-Id: I2f6e2c3777912eb2c522a54bbbee579ee37ee58a
Reviewed-on: https://boringssl-review.googlesource.com/7570
Reviewed-by: David Benjamin <davidben@google.com>
This commit is contained in:
David Benjamin 2016-03-25 18:56:10 -04:00
parent 44477c03b9
commit 1e4ae00ac2
1 changed files with 6 additions and 2 deletions
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8
ssl/t1_lib.c
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@ -2037,6 +2037,9 @@ static const struct tls_extension kExtensions[] = {
ext_ec_point_parse_clienthello, ext_ec_point_parse_clienthello,
ext_ec_point_add_serverhello, ext_ec_point_add_serverhello,
}, },
/* The final extension must be non-empty. WebSphere Application Server 7.0 is
* intolerant to the last extension being zero-length. See
* https://crbug.com/363583. */
{ {
TLSEXT_TYPE_elliptic_curves, TLSEXT_TYPE_elliptic_curves,
ext_ec_curves_init, ext_ec_curves_init,
@ -2123,9 +2126,10 @@ int ssl_add_clienthello_tlsext(SSL *ssl, CBB *out, size_t header_len) {
* NB: because this code works out the length of all existing extensions * NB: because this code works out the length of all existing extensions
* it MUST always appear last. */ * it MUST always appear last. */
size_t padding_len = 0x200 - header_len; size_t padding_len = 0x200 - header_len;
/* Extensions take at least four bytes to encode. Always include least /* Extensions take at least four bytes to encode. Always include at least
* one byte of data if including the extension. WebSphere Application * one byte of data if including the extension. WebSphere Application
* Server 7.0 is intolerant to the last extension being zero-length. */ * Server 7.0 is intolerant to the last extension being zero-length. See
* https://crbug.com/363583. */
if (padding_len >= 4 + 1) { if (padding_len >= 4 + 1) {
padding_len -= 4; padding_len -= 4;
} else { } else {