Steps:
In moodle as LTI provider:
1. Enable LTI authentication.
2. Enable LTI enrollment.
3. Publish course as LTI.
In Canvas as a consumer:
4. Go to Canvas consumer course.
5. Add an external app using the cartridge xml url and the secret.
6. Test if Moodle content displays correctly in Canvas.

Expected behavior:
I should be able to see Moodle content inside Canvas.

Actual behavior:
Unable to see Moodle content in Canvas.
And, I see the following error in Moodle error logs:

Error writing to database: Data too long for column 'value' at row 1\nINSERT INTO mdl_enrol_lti_lti2_nonce (consumerid,value,expires) VALUES(?,?,?)\n[array (\n  0 => '8',\n  1 => 'mXvVJzAqKCSsp9cEwK2Shqq8OnJ2wgsZTrz1KKfhPYQ',\n  2 => 1483995900,\n)]

Observation:
The size limit for the column value in table mdl_enrol_lti_lti2_nonce is set to 32 but the nonce value coming from canvas is of 43 chars.

Bug reproduced on demo.moodle.net as well.