The public API function BIO_new_NDEF is a helper function used for streaming ASN.1 data via a BIO. It is primarily used internally to OpenSSL to support the SMIME, CMS and PKCS7 streaming capabilities, but may also be called directly by end user applications.
The function receives a BIO from the caller, prepends a new BIO_f_asn1 filter BIO onto the front of it to form a BIO chain, and then returns the new head of the BIO chain to the caller. Under certain conditions, for example if a CMS recipient public key is invalid, the new filter BIO is freed and the function returns a NULL result indicating a failure. However, in this case, the BIO chain is not properly cleaned up and the BIO passed by the caller still retains internal pointers to the previously freed filter BIO. If the caller then goes on to call BIO_pop() on the BIO then a use-after-free will occur. This will most likely result in a crash.
This scenario occurs directly in the internal function B64_write_ASN1() which may cause BIO_new_NDEF() to be called and will subsequently call BIO_pop() on the BIO. This internal function is in turn called by the public API functions PEM_write_bio_ASN1_stream, PEM_write_bio_CMS_stream, PEM_write_bio_PKCS7_stream, SMIME_write_ASN1, SMIME_write_CMS and SMIME_write_PKCS7.
Other public API functions that may be impacted by this include i2d_ASN1_bio_stream, BIO_new_CMS, BIO_new_PKCS7, i2d_CMS_bio_stream and i2d_PKCS7_bio_stream.
References
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The public API function
BIO_new_NDEFis a helper function used for streaming ASN.1 data via aBIO. It is primarily used internally to OpenSSL to support the SMIME, CMS and PKCS7 streaming capabilities, but may also be called directly by end user applications.The function receives a
BIOfrom the caller, prepends a newBIO_f_asn1filterBIOonto the front of it to form aBIOchain, and then returns the new head of theBIOchain to the caller. Under certain conditions, for example if a CMS recipient public key is invalid, the new filterBIOis freed and the function returns aNULLresult indicating a failure. However, in this case, theBIOchain is not properly cleaned up and theBIOpassed by the caller still retains internal pointers to the previously freed filterBIO. If the caller then goes on to callBIO_pop()on theBIOthen a use-after-free will occur. This will most likely result in a crash.This scenario occurs directly in the internal function
B64_write_ASN1()which may causeBIO_new_NDEF()to be called and will subsequently callBIO_pop()on theBIO. This internal function is in turn called by the public API functionsPEM_write_bio_ASN1_stream,PEM_write_bio_CMS_stream,PEM_write_bio_PKCS7_stream,SMIME_write_ASN1,SMIME_write_CMSandSMIME_write_PKCS7.Other public API functions that may be impacted by this include
i2d_ASN1_bio_stream,BIO_new_CMS,BIO_new_PKCS7,i2d_CMS_bio_streamandi2d_PKCS7_bio_stream.References