Dogs and pigs, and all of their body parts are najis. Therefore, their leather is also najis.
The grand maraje’ state: Dogs and pigs that live on land are najis, including their hair, bones, paws, nails, and any wetness they excrete.
For further information on the rulings regarding dogs, refer to the following questions: 2827 (website: 3055), 1305 (website: 1291), 3430 (website: 4155). For information on different types of leather, see: Question 451 (website: 484).
 Tawdih al-Masaa’il (annotated by Imam Khomeini), vol. 1, pg. 75, issue 105.
This question does not have a detailed answer.