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Fix infinite loop in run_fs()#2262

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drwetter merged 1 commit intotestssl:3.1devfrom
dcooper16:run_fs_infnite_loop
Nov 10, 2022
Merged

Fix infinite loop in run_fs()#2262
drwetter merged 1 commit intotestssl:3.1devfrom
dcooper16:run_fs_infnite_loop

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This PR fixes an infinite loop in run_fs() that occurs in cases in which $OPENSSL supports TLS 1.3 and the server supports all of the non-TLS 1.3 FS ciphers that $OPENSSL supports but not all of the TLS 1.3 ciphers that $OPENSSL supports.

The problem is that testing for supported ciphers using $OPENSSL, testing should stop if there are no more ciphers to test (because all of the ciphers supported by $OPENSSL have been determined to be supported by the server). However, currently testing only stops if both the list of TLS 1.3 ciphers and non-TLS 1.3 ciphers is empty. In the problematic case, only the list of non-TLS 1.3 ciphers is empty. Instead of stopping, s_client_options() is called with a -cipher option with an empty list, and s_client_options() simply removes the -cipher option from the command, resulting in a call to $OPENSSL s_client with a full list of non-TLS 1.3 ciphers. Since this call succeeds, the loop continues.

This PR fixes the problem by stopping TLS 1.3 ClientHello testing when the list of TLS 1.3 ciphers is empty and stopping non-TLS 1.3 ClientHello testing when the list of non-TLS 1.3 ciphers is empty.

This commit fixes an infinite loop in run_fs() that occurs in cases in which $OPENSSL supports TLS 1.3 and the server supports all of the non-TLS 1.3 FS ciphers that $OPENSSL supports but not all of the TLS 1.3 ciphers that $OPENSSL supports.

The problem is that testing for supported ciphers using $OPENSSL, testing should stop if there are no more ciphers to test (because all of the ciphers supported by $OPENSSL have been determined to be supported by the server). However, currently testing only stops if both the list of TLS 1.3 ciphers and non-TLS 1.3 ciphers is empty. In the problematic case, only the list of non-TLS 1.3 ciphers is empty. Instead of stopping, s_client_options() is called with a -cipher option with an empty list, and s_client_options() simply removes the -cipher option from the command, resulting in a call to $OPENSSL s_client with a full list of non-TLS 1.3 ciphers. Since this call succeeds, the loop continues.

This commit fixes the problem by stopping TLS 1.3 ClientHello testing when the list of TLS 1.3 ciphers is empty and stopping non-TLS 1.3 ClientHello testing when the list of non-TLS 1.3 ciphers is empty.
@drwetter drwetter merged commit 2b0fdfd into testssl:3.1dev Nov 10, 2022
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Thanks!

@dcooper16 dcooper16 deleted the run_fs_infnite_loop branch November 10, 2022 14:48
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2 participants