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Document the d2i object reuse changes in PORTING.md.

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Change-Id: I1875c5246c7da19af13683ca36c737c188a97d18
Reviewed-on: https://boringssl-review.googlesource.com/6984
Reviewed-by: Adam Langley <agl@google.com>
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David Benjamin 2016-01-23 11:53:33 -05:00 committed by Adam Langley
parent bf3335c621
commit 4aafe6a3af
1 changed files with 23 additions and 0 deletions
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PORTING.md
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@ -130,6 +130,23 @@ BoringSSL's `BN_bn2hex` function uses lowercase hexadecimal digits instead of
uppercase. Some code may require changes to avoid being sensitive to this uppercase. Some code may require changes to avoid being sensitive to this
difference. difference.
### Legacy ASN.1 functions
OpenSSL's ASN.1 stack uses `d2i` functions for parsing. They have the form:
RSA *d2i_RSAPrivateKey(RSA **out, const uint8_t **inp, long len);
In addition to returning the result, OpenSSL places it in `*out` if `out` is
not `NULL`. On input, if `*out` is not `NULL`, OpenSSL will usually (but not
always) reuse that object rather than allocating a new one. In BoringSSL, these
functions are compatibility wrappers over a newer ASN.1 stack. Even if `*out`
is not `NULL`, these wrappers will always allocate a new object and free the
previous one.
Ensure that callers do not rely on this object reuse behavior. It is
recommended to avoid the `out` parameter completely and always pass in `NULL`.
Note that less error-prone APIs are available for BoringSSL-specific code (see
below).
## Optional BoringSSL-specific simplifications ## Optional BoringSSL-specific simplifications
@ -162,3 +179,9 @@ locks. Without initializing these, the library is not thread-safe. Configuring
these does nothing in BoringSSL. Instead, BoringSSL calls pthreads and the these does nothing in BoringSSL. Instead, BoringSSL calls pthreads and the
corresponding Windows APIs internally and is always thread-safe where the API corresponding Windows APIs internally and is always thread-safe where the API
guarantees it. guarantees it.
### ASN.1
BoringSSL is in the process of deprecating OpenSSL's `d2i` and `i2d` in favor of
new functions using the much less error-prone `CBS` and `CBB` types.
BoringSSL-only code should use those functions where available.