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Fix potential stack underflow in mpi_read_file.

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When provided with an empty line, mpi_read_file causes a numeric
underflow resulting in a stack underflow. This commit fixes this and
adds some documentation to mpi_read_file.
This commit is contained in:
Hanno Becker 2017-04-26 11:46:46 +01:00
parent b65c2be5f1
commit b2034b7785
3 changed files with 20 additions and 4 deletions
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6
library/bignum.c
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@ -616,11 +616,11 @@ int mbedtls_mpi_read_file( mbedtls_mpi *X, int radix, FILE *fin )
if( slen == sizeof( s ) - 2 )
return( MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL );
if( s[slen - 1] == '\n' ) { slen--; s[slen] = '\0'; }
if( s[slen - 1] == '\r' ) { slen--; s[slen] = '\0'; }
if( slen > 0 && s[slen - 1] == '\n' ) { slen--; s[slen] = '\0'; }
if( slen > 0 && s[slen - 1] == '\r' ) { slen--; s[slen] = '\0'; }
p = s + slen;
while( --p >= s )
while( p-- > s )
if( mpi_get_digit( &d, radix, *p ) != 0 )
break;