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Merge pull request #4096 from gilles-peskine-arm/mpi_sub_abs-buffer_overflow-development

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Fix buffer overflow in mbedtls_mpi_sub_abs negative case
This commit is contained in:
Janos Follath 2021-02-02 13:10:31 +00:00 committed by GitHub
commit bbd2bfb666
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3 changed files with 29 additions and 4 deletions
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7
ChangeLog.d/mpi_sub_abs.txt Normal file
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@ -0,0 +1,7 @@
Security
* Fix a buffer overflow in mbedtls_mpi_sub_abs() when calculating
|A| - |B| where |B| is larger than |A| and has more limbs (so the
function should return MBEDTLS_ERR_MPI_NEGATIVE_VALUE). Only
applications calling mbedtls_mpi_sub_abs() directly are affected:
all calls inside the library were safe since this function is
only called with |A| >= |B|. Reported by Guido Vranken in #4042.

6
library/bignum.c
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@ -1401,6 +1401,12 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
for( n = B->n; n > 0; n-- )
if( B->p[n - 1] != 0 )
break;
if( n > A->n )
{
/* B >= (2^ciL)^n > A */
ret = MBEDTLS_ERR_MPI_NEGATIVE_VALUE;
goto cleanup;
}
carry = mpi_sub_hlp( n, X->p, B->p );
if( carry != 0 )

20
tests/suites/test_suite_mpi.data
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@ -484,18 +484,30 @@ mbedtls_mpi_add_int:10:"20395687835640197740576586692903457728019399331434826309
Test mbedtls_mpi_add_int #2
mbedtls_mpi_add_int:10:"2039568783564019774057658669290345772801939933143482630947726464532830627227012776329":-9871232:10:"2039568783564019774057658669290345772801939933143482630947726464532830627227002905097"
Base test mbedtls_mpi_sub_abs #1 (Test with larger second input)
Base test mbedtls_mpi_sub_abs #1 (|B| > |A|)
mbedtls_mpi_sub_abs:10:"5":10:"7":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #2 (Test with larger second input)
Base test mbedtls_mpi_sub_abs #2 (|B| > |A|)
mbedtls_mpi_sub_abs:10:"-5":10:"-7":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #3 (Test with larger second input)
Base test mbedtls_mpi_sub_abs #3 (|B| > |A|)
mbedtls_mpi_sub_abs:10:"-5":10:"7":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #4 (Test with larger second input)
Base test mbedtls_mpi_sub_abs #4 (|B| > |A|)
mbedtls_mpi_sub_abs:10:"5":10:"-7":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #1 (|B| >> |A| with more limbs)
mbedtls_mpi_sub_abs:10:"5":16:"123456789abcdef01":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #2 (|B| >> |A| with more limbs)
mbedtls_mpi_sub_abs:10:"-5":16:"-123456789abcdef01":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #3 (|B| >> |A| with more limbs)
mbedtls_mpi_sub_abs:10:"-5":16:"123456789abcdef01":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #4 (|B| >> |A| with more limbs)
mbedtls_mpi_sub_abs:10:"5":16:"-123456789abcdef01":10:"0":MBEDTLS_ERR_MPI_NEGATIVE_VALUE
Base test mbedtls_mpi_sub_abs #1
mbedtls_mpi_sub_abs:10:"7":10:"5":10:"2":0