75 lines
2.8 KiB
Diff
75 lines
2.8 KiB
Diff
commit 0238eb8f3612515f4374381b593dd79116169330
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Author: John Dennis <jdennis@redhat.com>
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Date: Thu Aug 2 16:21:33 2018 -0400
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fix concatkdf failures on big endian architectures
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Several of the elements used to compute the digest in ECDH-ES key
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agreement computation are represented in binary form as a 32-bit
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integer length followed by that number of octets. the length
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field. The 32-bit length integer is represented in big endian
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format (the 8 most significant bits are in the first octet.).
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The conversion to a 4 byte big endian integer was being computed
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in a manner that only worked on little endian architectures. The
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function htonl() returns a 32-bit integer whose octet sequence given
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the address of the integer is big endian. There is no need for any
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further manipulation.
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The existing code used bit shifting on a 32-bit value. In C bit
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shifting is endian agnostic for multi-octet values, a right shift
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moves most significant bits toward least significant bits. The result
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of a bit shift of a multi-octet value on either big or little
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archictures will always be the same provided you "view" it as the same
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data type (e.g. 32-bit integer). But indexing the octets of that
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mulit-octet value will be different depending on endianness, hence the
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assembled octets differed depending on endianness.
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Issue: #77
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Signed-off-by: John Dennis <jdennis@redhat.com>
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diff --git a/src/concatkdf.c b/src/concatkdf.c
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index ec064ab..59b845a 100644
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--- a/src/concatkdf.c
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+++ b/src/concatkdf.c
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@@ -29,15 +29,9 @@
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////////////////////////////////////////////////////////////////////////////////
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static uint8_t *_apply_uint32(const uint32_t value, uint8_t *buffer)
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{
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- const uint32_t formatted = htonl(value);
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- const uint8_t data[4] = {
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- (formatted >> 0) & 0xff,
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- (formatted >> 8) & 0xff,
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- (formatted >> 16) & 0xff,
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- (formatted >> 24) & 0xff
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- };
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- memcpy(buffer, data, 4);
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+ const uint32_t big_endian_int32 = htonl(value);
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+ memcpy(buffer, &big_endian_int32, 4);
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return buffer + 4;
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}
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diff --git a/test/check_concatkdf.c b/test/check_concatkdf.c
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index e4325fc..41d0f1c 100644
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--- a/test/check_concatkdf.c
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+++ b/test/check_concatkdf.c
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@@ -60,14 +60,9 @@ _create_otherinfo_header_finish:
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static bool _cmp_uint32(uint8_t **actual, uint32_t expected)
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{
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- uint32_t value = htonl(expected);
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- uint8_t expectedData[] = {
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- (value >> 0) & 0xff,
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- (value >> 8) & 0xff,
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- (value >> 16) & 0xff,
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- (value >> 24) & 0xff
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- };
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- bool result = (0 == memcmp(*actual, expectedData, 4));
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+ uint32_t big_endian_int32 = htonl(expected);
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+
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+ bool result = (0 == memcmp(*actual, &big_endian_int32, 4));
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(*actual) += 4;
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return result;
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}
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